Conversion of units 1 Conversion of units Conversion of units refers to conversion factors between different units of measurement for the same quantity. Techniques Process The process of conversion depends on the specific situation and the intended purpose. This may be governed by regulation, contract, Technical specifications or other published standards. Engineering judgment may include such factors as: • The precision and accuracy of measurement and the associated uncertainty of measurement • The statistical confidence interval or tolerance interval of the initial measurement • The number of significant figures of the measurement • The intended use of the measurement including the engineering tolerances Some conversions from one system of units to another need to be exact, without increasing or decreasing the precision of the first measurement. This is sometimes called soft conversion. It does not involve changing the physical configuration of the item being measured. By contrast, a hard conversion or an adaptive conversion may not be exactly equivalent. It changes the measurement to convenient and workable numbers and units in the new system. It sometimes involves a slightly different configuration, or size substitution, of the item. Multiplication Factors Conversion between units in the metric (SI) system can be discerned by their prefixes (for example, 1 kilogram = 1000 grams, 1 milligram = 0.001 grams) and are thus not listed in this article. Exceptions are made if the unit is commonly known by another name (for example, 1 micron = 10 −6 metre). For a full listing of multiplication factors, see SI prefix. Table Ordering Within each table, the units are listed alphabetically, and the SI units (base or derived) are highlighted. Tables of conversion factors This article gives lists of conversion factors for each of a number of physical quantities, which are listed in the index. For each physical quantity, a number of different units (some only of historical interest) are shown and expressed in terms of the corresponding SI unit.
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Conversion of units - SMART & COMPETITIVE · Conversion of units 2 Legend Symbol Definition ≡ exactly equal to ≈ approximately equal to digits indicates that digits repeat infinitely
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Conversion of units 1
Conversion of unitsConversion of units refers to conversion factors between different units of measurement for the same quantity
Techniques
ProcessThe process of conversion depends on the specific situation and the intended purpose This may be governed byregulation contract Technical specifications or other published standards Engineering judgment may include suchfactors asbull The precision and accuracy of measurement and the associated uncertainty of measurementbull The statistical confidence interval or tolerance interval of the initial measurementbull The number of significant figures of the measurementbull The intended use of the measurement including the engineering tolerancesSome conversions from one system of units to another need to be exact without increasing or decreasing theprecision of the first measurement This is sometimes called soft conversion It does not involve changing thephysical configuration of the item being measuredBy contrast a hard conversion or an adaptive conversion may not be exactly equivalent It changes the measurementto convenient and workable numbers and units in the new system It sometimes involves a slightly differentconfiguration or size substitution of the item
Multiplication FactorsConversion between units in the metric (SI) system can be discerned by their prefixes (for example 1 kilogram =1000 grams 1 milligram = 0001 grams) and are thus not listed in this article Exceptions are made if the unit iscommonly known by another name (for example 1 micron = 10minus6 metre) For a full listing of multiplication factorssee SI prefix
Table OrderingWithin each table the units are listed alphabetically and the SI units (base or derived) are highlighted
Tables of conversion factorsThis article gives lists of conversion factors for each of a number of physical quantities which are listed in the indexFor each physical quantity a number of different units (some only of historical interest) are shown and expressed interms of the corresponding SI unit
Conversion of units 2
Legend
Symbol Definition
equiv exactly equal to
asymp approximately equal to
digits indicates that digits repeat infinitely (eg 8294 369 corresponds to 8294 369 369 369 369hellip)
(H) of chiefly historical interest
Length
Length
Name of unit Symbol Definition Relation to SI units
aringngstroumlm Aring equiv 1 times 10minus10 m equiv 01 nm
astronomical unit AU asymp Distance from Earth to Sun asymp 149 597 871 464 m [1]
barleycorn (H) = ⅓ in (see note above about rounding) asymp 846 times 10minus3 m
bohr atomic unit oflength
a0 equiv Bohr radius of hydrogen asymp 5291 772 0859 times 10minus11 plusmn36 times 10minus20 m [2]
cable length (Imperial) equiv 608 ft asymp 1853184 m
Name of unit Symbol Definition Relation to SIunits
angular mil micro equiv 2π6400 rad asymp 0981 748 times 10minus3
rad
arcminute equiv 1deg60 asymp 0290 888 times 10minus3
rad
arcsecond equiv 1deg3600 asymp 4848 137 times 10minus6
rad
centesimal minuteof arc
equiv 1 grad100 asymp 0157 080 times 10minus3
rad
centesimal secondof arc
equiv 1 grad(10 000) asymp 1570 796 times 10minus6
rad
degree (of arc) deg equiv 1360 of a revolution equiv π180 rad asymp 17453293 times 10minus3 rad
grad gradian gon grad equiv 1400 of a revolution equiv 2π400 rad equiv 09deg asymp 15707963 times 10minus3 rad
octant equiv 45deg asymp 0785 398 rad
quadrant equiv 90deg asymp 1570 796 rad
radian (SI unit) rad The angle subtended at the center of a circle by an arc whose length is equal to the circlesradius One full revolution encompasses 2π radians
= 1 rad
sextant equiv 60deg asymp 1047 198 rad
sign equiv 30deg asymp 0523 599 rad
Conversion of units 10
Solid angle
Solid angle
Name of unit Symbol Definition Relation to SIunits
steradian (SIunit)
sr The solid angle subtended at the center of a sphere of radius r by a portion of the surface of the spherehaving an area r2 A sphere encompasses 4π sr[14]
= 1 sr
MassNotesbull See Weight for detail of massweight distinction and conversionbull In this table the unit gee is used to denote standard gravity in order to avoid confusion with the g symbol for
gramsbull In physics the pound of mass is sometimes written lbm to distinguish it from the pound-force (lbf) It should not
be read as the mongrel unit pound metre
Mass
Name of unit Symbol Definition Relation to SI units
atomic mass unit unified u AMU asymp 1660 538 73 times 10minus27 plusmn 13 times 10minus36 kg
atomic unit of mass electron restmass
me asymp 9109 382 15 times 10minus31 plusmn 45 times 10minus39 kg[18]
bag (coffee) equiv 60 kg = 60 kg
bag (Portland cement) equiv 94 lb av = 42637 682 78 kg
barge equiv 22frac12 sh tn = 20 411656 65 kg
carat kt equiv 3 16 gr asymp 205196 548 333 mg
carat (metric) ct equiv 200 mg = 200 mg
clove equiv 8 lb av = 3628 738 96 kg
crith asymp 899349 mg
dalton Da asymp 1660 902 10 times 10minus27 plusmn 13 times 10minus36 kg
dram (apothecary troy) dr t equiv 60 gr = 3887 9346 g
dram (avoirdupois) dr av equiv 27 1132 gr = 1771 845 195 3125 g
electronvolt eV equiv 1 eV (energy unit) c2 = 17826 times 10minus36 kg
gamma γ equiv 1 μg = 1 μg
grain gr equiv 17000 lb av equiv 64798 91 mg
grave G grave was the original name of the kilogram equiv 1 kg
hundredweight (long) long cwt orcwt
equiv 112 lb av = 50802 345 44 kg
hundredweight (short) cental sh cwt equiv 100 lb av = 45359 237 kg
hyl (CGS unit) equiv 1 gee times 1 g times 1 s2m = 9806 65 g
hyl (MKS unit) equiv 1 gee times 1 kg times 1 s2m = 9806 65 kg
Conversion of units 11
kilogram kg equiv mass of the prototype near Paris (asymp mass of 1L ofwater)
equiv 1 kg (SI base unit)[8]
kip kip equiv 1000 lb av = 453592 37 kg
mark equiv 8 oz t = 248827 8144 g
mite equiv 120 gr = 3239 9455 mg
mite (metric) equiv 120 g = 50 mg
ounce (apothecary troy) oz t equiv 112 lb t = 31103 4768 g
ounce (avoirdupois) oz av equiv 116 lb = 28349 523 125 g
ounce (US food nutritionlabeling)
oz equiv 28 g[16] = 28 g
pennyweight dwt pwt equiv 120 oz t = 1555 173 84 g
point equiv 1100 ct = 2 mg
pound (avoirdupois) lb av equiv 0453 592 37 kg = 7000 grains equiv 0453 592 37 kg
pound (metric) equiv 500 g = 500 g
pound (troy) lb t equiv 5 760 grains = 0373 241 7216 kg
quarter (Imperial) equiv 14 long cwt = 2 st = 28 lb av = 12700 586 36 kg
quarter (informal) equiv frac14 short tn = 226796 185 kg
quarter long (informal) equiv frac14 long tn = 254011 7272 kg
quintal (metric) q equiv 100 kg = 100 kg
scruple (apothecary) s ap equiv 20 gr = 1295 9782 g
sheet equiv 1700 lb av = 6479891 mg
slug geepound slug equiv 1 gee times 1 lb av times 1 s2ft asymp 14593 903 kg
stone st equiv 14 lb av = 6350 293 18 kg
ton assay (long) AT equiv 1 mg times 1 long tn divide 1 oz t asymp 32666 667 g
ton assay (short) AT equiv 1 mg times 1 sh tn divide 1 oz t asymp 29166 667 g
ton long long tn or ton equiv 2 240 lb = 1 016046 9088 kg
ton short sh tn equiv 2 000 lb = 907184 74 kg
tonne (mts unit) t equiv 1 000 kg = 1 000 kg
wey equiv 252 lb = 18 st = 114305 277 24 kg (variants exist)
Zentner Ztr Definitions vary see [19] and[14]
Density
Conversion of units 12
Density
Name of unit Symbol Definition Relation to SI units
gram per millilitre gmL equiv gmL = 1000 kgm3
kilogram per cubic metre (SI unit) kgm3 equiv kgm3 = 1 kgm3
slug per cubic foot slugft3 equiv slugft3 asymp 5153788184 kgm3
Time
Time t
Name of unit Symbol Definition Relation to SI units
atomic unit of time au equiv a0(αmiddotc) asymp 2418 884 254 times 10minus17
s
Callippic cycle equiv 441 mo (hollow) + 499 mo (full) = 76 a of 36525 d = 2398 3776 times 109 s
century c equiv 100 a (see below for definition of year length) = 100 times year
day d = 24 h = 86400 s
day (sidereal) d equiv Time needed for the Earth to rotate once around its axisdetermined from successive transits of a very distantastronomical object across an observers meridian(International Celestial Reference Frame)
asymp 86 1641 s
decade dec equiv 10 a (see below for definition of year length) = 10 times year
fortnight fn equiv 2 wk = 1 209 600 s
helek equiv 11 080 h = 33 s
Hipparchic cycle equiv 4 Callippic cycles - 1 d = 9593 424 times 109 s
hour h equiv 60 min = 3 600 s
jiffy j equiv 160 s = 016 s
jiffy (alternate) ja equiv 1100 s = 10 ms
ke (quarter of an hour) equiv frac14 h = 196 d = 60 times 60 4 s = 900 s= 60 4 min = 15 min
Conversion of units 13
ke (traditional) equiv 1100 d = 24 times 60 times 60 100 s =864 s = 24 60 100min = 144 min
lustre lustrum equiv 5 a of 365 d = 15768 times 108 s
Metonic cycle enneadecaeteris equiv 110 mo (hollow) + 125 mo (full) = 6940 d asymp 19 a = 5996 16 times 108 s
millennium equiv 1 000 a (see below for definition of year length) = 1000 times year
milliday md equiv 11 000 d = 24 times 60 times 60 1 000 s= 864 s
minute min equiv 60 s due to leap seconds sometimes 59 s or 61 s = 60 s
moment equiv 90 s = 90 s
month (full) mo equiv 30 d[20] = 2 592 000 s
month (Greg av) mo Average Gregorian month = 365242512 d = 30436875 d asymp 26297 times 106 s
month (hollow) mo equiv 29 d[20] = 2 505 600 s
month (synodic) mo Cycle time of moon phases asymp 29530589 days (Average) asymp 2551 times 106 s
octaeteris = 48 mo (full) + 48 mo (hollow) + 3 mo (full)[21] [22] = 8 aof 36525 d = 2922 d
= 2524 608 times 108 s
Planck time equiv (Gℏc5)frac12 asymp 1351 211 868 times 10minus43
s
second s time of 9 192 631 770 periods of the radiation correspondingto the transition between the 2 hyperfine levels of the groundstate of the caesium 133 atom at 0 K[8] (but other secondsare sometimes used in astronomy)
(SI base unit)
shake equiv 10minus8 s = 10 ns
sigma equiv 10minus6 s = 1 μs
Sothic cycle equiv 1 461 a of 365 d = 4607 4096 times 1010 s
svedberg S equiv 10minus13 s = 100 fs
week wk equiv 7 d = 604 800 s
year (Gregorian) a y oryr
= 3652425 d average calculated from common years (365d) plus leap years (366 d) on most years divisible by 4 Seeleap year for details
= 31 556 952 s
year (Julian) a y oryr
= 36525 d average calculated from common years (365 d)plus one leap year (366 d) every four years
= 31 557 600 s
year (sidereal) a y oryr
equiv time taken for Sun to return to the same position withrespect to the stars of the celestial sphere
asymp 365256 363 d asymp 31558 1497632 s
year (tropical) a y oryr
equiv Length of time it takes for the Sun to return to the sameposition in the cycle of seasons
asymp 365242 190 d asymp 31556 925 s
Where UTC is observed the length of timeunits longer than 1 s may increase or decreaseby 1 s if a leap second occurs during the timeinterval of interest
Conversion of units 14
Frequency
Frequency
Name of unit Symbol Definition Relation to SI units
hertz (SI unit) Hz equiv Number of cycles per second = 1 Hz = 1s
revolutions per minute rpm equiv One unit rpm equals one rotation completed around a fixed axis in one minute of time asymp0104719755 rads
Speed or velocity
Speed
Name of unit Symbol Definition Relation to SI units
foot per hour fph equiv 1 fth asymp 8466 667 times 10minus5
ms
foot per minute fpm equiv 1 ftmin = 508 times 10minus3 ms
foot per second fps equiv 1 fts = 3048 times 10minus1 ms
furlong perfortnight
equiv furlongfortnight asymp 1663 095 times 10minus4
ms
inch per minute ipm equiv 1 inmin asymp 423 333 times 10minus4 ms
inch per second ips equiv 1 ins = 254 times 10minus2 ms
mach number M Ratio of the speed to the speed of sound in the medium Varies especially with temperatureAbout 761 mph (1225 kph) in air at sea level to about 660 mph (1062 kph) at jet altitudesUnitless
asymp 340 to 295 ms foraircraft
metre per second(SI unit)
ms equiv 1 ms = 1 ms
mile per hour mph equiv 1 mih = 0447 04 ms
mile per minute mpm equiv 1 mimin = 268224 ms
mile per second mps equiv 1 mis = 1 609344 ms
speed of light invacuum
c equiv 299 792 458 ms = 299 792 458 ms
speed of sound inair
s Varies especially with temperature About 761 mph (1225 kph) in air at sea level to about660 mph (1062 kph) at jet altitudes
asymp 340 to 295 ms ataircraft altitudes
A velocity consists of a speed combined with a direction the speed part of the velocity takes units of speed
Conversion of units 15
Flow (volume)
Flow
Name of unit Symbol Definition Relation to SI units
cubic foot per minute CFM equiv 1 ft3min = 4719474432 times 10minus4 m3s
cubic foot per second ft3s equiv 1 ft3s = 0028316846592 m3s
cubic inch per minute in3min equiv 1 in3min = 27311773 times 10minus7 m3s
cubic inch per second in3s equiv 1 in3s = 16387064 times 10minus5 m3s
cubic metre per second (SIunit)
m3s equiv 1 m3s = 1 m3s
gallon (US fluid) per day GPD equiv 1 gald = 4381263638 times 10minus8 m3s
gallon (US fluid) per hour GPH equiv 1 galh = 1051503273 times 10minus6 m3s
gallon (US fluid) per minute GPM equiv 1 galmin = 630901964 times 10minus5 m3s
litre per minute LPM equiv 1 Lmin = 16 times 10minus5 m3s
Acceleration
Acceleration
Name of unit Symbol Definition Relation to SI units
foot per hour per second fphs equiv 1 ft(hmiddots) asymp 8466 667 times 10minus5
ms2
foot per minute per second fpms equiv 1 ft(minmiddots) = 508 times 10minus3 ms2
foot per second squared fps2 equiv 1 fts2 = 3048 times 10minus1 ms2
gal galileo Gal equiv 1 cms2 = 10minus2 ms2
inch per minute per second ipms equiv 1 in(minmiddots) asymp 4233 333 times 10minus4
ms2
inch per second squared ips2 equiv 1 ins2 = 254 times 10minus2 ms2
knot per second kns equiv 1 kns asymp 5144 444 times 10minus1
ms2
metre per second squared (SI unit) ms2 equiv 1 ms2 = 1 ms2
mile per hour per second mphs equiv 1 mi(hmiddots) = 44704 times 10minus1 ms2
mile per minute per second mpms equiv 1 mi(minmiddots) = 268224 ms2
mile per second squared mps2 equiv 1 mis2 = 1609 344 times 103 ms2
standard gravity g equiv 9806 65 ms2 = 9806 65 ms2
Conversion of units 16
Force
Force
Name of unit Symbol Definition Relation to SI units
atomic unit of force equiv memiddotα2middotc2a0 asymp 8238 722 06 times 10minus8 N
[23]
dyne (cgs unit) dyn equiv gmiddotcms2 = 10minus5 N
kilogram-force kilopondgrave-force
kgf kp Gf equiv g times 1 kg = 9806 65 N
kip kip-force kip kipfklbf
equiv g times 1 000 lb = 4448 221 6152605 times 103 N
milligrave-force gravet-force mGf gf equiv g times 1 g = 9806 65 mN
newton (SI unit) N A force capable of giving a mass of one kg an acceleration of one metreper second per second[24]
= 1 N = 1 kgmiddotms2
ounce-force ozf equiv g times 1 oz = 0278 013 850 9537812 N
pound lb equiv slugmiddotfts2 = 4448 230 531 N
pound-force lbf equiv g times 1 lb = 4448 221 615 2605 N
poise (cgs unit) P equiv 10minus1 Pamiddots = 01 Pamiddots
pound per foot hour lb(ftmiddoth) equiv 1 lb(ftmiddoth) asymp 4133 789 times 10minus4 Pamiddots
pound per foot second lb(ftmiddots) equiv 1 lb(ftmiddots) asymp 1488164 Pamiddots
pound-force second per square foot lbfmiddotsft2 equiv 1 lbfmiddotsft2 asymp 4788026 Pamiddots
pound-force second per square inch lbfmiddotsin2 equiv 1 lbfmiddotsin2 asymp 6894757 Pamiddots
Conversion of units 21
Kinematic viscosity
Kinematic viscosity
Name of unit Symbol Definition Relation to SI units
square foot per second ft2s equiv 1 ft2s = 009290304 m2s
square metre per second (SI unit) m2s equiv 1 m2s = 1 m2s
stokes (cgs unit) St equiv10minus4 m2s
= 10minus4 m2s
Electric current
Electric current
Name of unit Symbol Definition Relation to SI units
ampere (SI base unit) A equiv The constant current needed to produce a force of 2 times 10minus7 newton per metre betweentwo straight parallel conductors of infinite length and negligible circular cross-sectionplaced one metre apart in a vacuum[8]
= 1 A
electromagnetic unitabampere (cgs unit)
abamp equiv 10 A = 10 A
esu per secondstatampere (cgs unit)
esus equiv (01 Amiddotms) c asymp3335641 times 10minus10 A
Electric charge
Electric charge
Name of unit Symbol Definition Relation to SI units
abcoulomb electromagnetic unit (cgsunit)
abC emu equiv 10 C = 10 C
atomic unit of charge au equiv e asymp 1602 176462 times 10minus19 C
coulomb (SI unit) C equiv The amount of electricity carried in one second of time by oneampere of current[24]
= 1 C = 1 Amiddots
faraday F equiv 1 mol times NAmiddote asymp 96 4853383 C
statcoulomb franklin electrostatic unit(cgs unit)
statC Fresu
equiv (01 Amiddotm) c asymp 3335 641 times 10minus10 C
Conversion of units 22
Electric dipole
Electric dipole
Name of unit Symbol Definition Relation to SI units
atomic unit of electric dipole moment ea0 asymp 8478 352 81 times 10minus30
Cmiddotm[28]
Electromotive force electric potential difference
Voltage electromotive force
Name ofunit
Symbol Definition Relation to SI units
abvolt (cgsunit)
abV equiv 1 times 10minus8 V = 1 times 10minus8 V
statvolt (cgsunit)
statV equiv cmiddot (1 μJAmiddotm) = 299792 458 V
volt (SIunit)
V The difference in electric potential across two points along a conducting wire carrying one ampereof constant current when the power dissipated between the points equals one watt[24]
= 1 V = 1 WA = 1kgmiddotm2(Amiddots3)
Electrical resistance
Electrical resistance
Name ofunit
Symbol Definition Relation to SI units
ohm (SIunit)
Ω The resistance between two points in a conductor when one volt of electric potential differenceapplied to these points produces one ampere of current in the conductor[24]
= 1 Ω = 1 VA = 1kgmiddotm2(A2middots3)
Capacitance
Capacitors ability to store charge
Name ofunit
Symbol Definition Relation to SI units
farad (SIunit)
F The capacitance between two parallel plates that results in one volt of potential difference whencharged by one coulomb of electricity[24]
= 1 F = 1 CV = 1A2middots4(kgmiddotm2)
Conversion of units 23
Magnetic flux
magnetic flux
Name of unit Symbol Definition Relation to SI units
maxwell (CGSunit)
Mx equiv 10minus8 Wb[29] = 1 times 10minus8 Wb
weber (SIunit)
Wb Magnetic flux which linking a circuit of one turn would produce in it an electromotive force of1 volt if it were reduced to zero at a uniform rate in 1 second[24]
= 1 Wb = 1 Vmiddots = 1kgmiddotm2(Amiddots2)
Magnetic flux density
What physicists call Magnetic field is called Magnetic flux density by electrical engineersand magnetic induction by applied mathematicians and electrical engineers
Name of unit Symbol Definition Relation to SI units
gauss (CGS unit) G equiv Mxcm2 = 10minus4
T= 1 times 10minus4 T [30]
tesla (SI unit) T equiv Wbm2 = 1 T = 1 Wbm2 = 1kg(Amiddots2)
Inductance
Inductance
Name ofunit
Symbol Definition Relation to SI units
henry (SIunit)
H The inductance of a closed circuit that produces one volt of electromotive force when the current inthe circuit varies at a uniform rate of one ampere per second[24]
= 1 H = 1 WbA = 1kgmiddotm2(Amiddots)2
Temperature
Temperature
Name of unit Symbol Definition Conversion to kelvin
degree Celsius degC degC equiv K minus 27315 [K] equiv [degC] + 27315
degree Delisle degDe [K] = 37315 minus [degDe] times 23
degree Fahrenheit degF degF equiv degC times 95 + 32 [K] equiv ([degF] + 45967) times 59
degree Newton degN [K] = [degN] times 10033 + 27315
degree Rankine degR degRa degR equiv K times 95 [K] equiv [degR] times 59
degree Reacuteaumur degReacute [K] = [degReacute] times 54 + 27315
degree Roslashmer degRoslash [K] = ([degRoslash] minus 75) times 4021 + 27315
kelvin (SI baseunit)
K equiv 127316 of the thermodynamic temperature of the triple point of water[8] equiv 1 K
Conversion of units 24
Information entropy
Information entropy
Name of unit Symbol Definition Relation to SI units Relation to bits
SI unit JK equiv JK = 1 JK
nat nip nepit nat equiv kB = 1380 650 5(23) times 10minus23 JK
bit shannon bit b Sh equiv ln(2) times kB = 9569 940 (16) times 10minus24 JK = 1 bit
ban hartley ban Hart equiv ln(10) times kB = 3179 065 3(53) times 10minus23 JK
nibble equiv 4 bits = 3827 976 0(64) times 10minus23 JK = 22 bit
byte B equiv 8 bits = 7655 952 (13) times 10minus23 JK = 23 bit
kilobyte (decimal) kB equiv 1 000 B = 7655 952 (13) times 10minus20 JK
kilobyte (kibibyte) KB KiB equiv 1 024 B = 7839 695 (13) times 10minus20 JK = 210 bit
Often information entropy is measured in shannons whereas the (discrete) storage space of digital devices ismeasured in bits Thus uncompressed redundant data occupy more than one bit of storage per shannon ofinformation entropy The multiples of a bit listed above are usually used with this meaning Other times the bit isused as a measure of information entropy and is thus a synonym of shannon
Luminous intensityThe candela is the preferred nomenclature for the SI unit
Luminous intensity
Name of unit Symbol Definition Relation toSI units
candela (SI baseunit) candle
cd The luminous intensity in a given direction of a source that emits monochromatic radiation offrequency 540 times 1012 hertz and that has a radiant intensity in that direction of 1683 watt persteradian[8]
= 1 cd
candlepower (new) cp equiv cd The use of candlepower as a unit is discouraged due to its ambiguity = 1 cd
candlepower (oldpre-1948)
cp Varies and is poorly reproducible[31] Approximately 0981 cd[14] asymp 0981 cd
Luminance
Conversion of units 25
Luminance
Name of unit Symbol Definition Relation to SI units
candela per square foot cdft2 equiv cdft2 asymp10763910417 cdm2
candela per square inch cdin2 equiv cdin2 asymp 15500031 cdm2
candela per square metre (SI unit) nit (deprecated[14] ) cdm2 equiv cdm2 = 1 cdm2
Name of unit Symbol Definition Relation to SI units
lumen (SIunit)
lm equiv cdmiddotsr = 1 lm = 1 cdmiddotsr
Illuminance
Illuminance
Name of unit Symbol Definition Relation to SI units
footcandle lumen per square foot fc equiv lmft2 = 10763910417 lx
lumen per square inch lmin2 equiv lmin2 asymp 15500031 lx
lux (SI unit) lx equiv lmm2 = 1 lx = 1 lmm2
phot (CGS unit) ph equiv lmcm2 = 1 times 104 lx
Radiation - source activity
Conversion of units 26
Radioactivity
Name of unit Symbol Definition Relation to SI units
becquerel (SIunit)
Bq equiv Number of disintegrations per second = 1 Bq = 1s
curie Ci equiv 37 times 1010 Bq = 37 times 1010 Bq [32]
rutherford (H) rd equiv 1 MBq = 1 times 106 Bq
Please note that although becquerel (Bq) and hertz (Hz) both ultimately refer to the same SI base unit (sminus1) Hz isused only for periodic phenomena and Bq is only used for stochastic processes associated with radioactivity[33]
Radiation - exposure
Radiation - exposure
Name of unit Symbol Definition Relation to SI units
roentgen R 1 R equiv 258 times 10minus4 Ckg[29] = 258 times 10minus4 Ckg
The roentgen is not a SI unit and the NIST strongly discourages its continued use[34]
Radiation - absorbed dose
Radiation - absorbed dose
Name of unit Symbol Definition Relation to SI units
Name of unit Symbol Definition Relation to SI units
Roumlntgen equivalent man rem equiv 001 Sv = 001 Sv
sievert (SI unit) Sv equiv 1 Jkg[33] = 1 Sv
Although the definitions for sievert (Sv) and gray (Gy) would seem to indicate that they measure the same quantitiesthis is not the case The effect of receiving a certain dose of radiation (given as Gy) is variable and depends on manyfactors thus a new unit was needed to denote the biological effectiveness of that dose on the body this is known asthe equivalent dose and is shown in Sv The general relationship between absorbed dose and equivalent dose can berepresented as
H = Q middot D
where H is the equivalent dose D is the absorbed dose and Q is a dimensionless quality factor Thus for anyquantity of D measured in Gy the numerical value for H measured in Sv may be different[36]
Conversion of units 27
Software toolsHome and office computers come with converters in bundled spreadsheet applications or can access free convertersvia the Internet Units and measurements can be easily converted using these tools but only if the units are explicitlydefined and the conversion is compatible (eg cmHg to kPa)
Free conversion softwarebull Units (software) a popular cross-platform command-line utilitybull Converter [37] contextual unit converter for Mozilla Firefox browsersbull Converber [38] portable application converting utilitybull calculla [39] calculla - online web convertersbull iMetrix [40] - unit converter for xpbull uniteasy [41] online scientific unit conversionbull Unit Converter Add-in for Excel [42] - allow a large selection of unit conversions within the Microsoft Excel
spread sheet programbull Unit Converter [43] simple and extensible unit converterbull Portable Unit Converter [44] including 4500 units 33 unit-categories and the possibility to create custom units
General commercial sources of convertersbull Advanced electronic calculators have unit-conversion functionalitybull Spreadsheet programs usually provide conversion functions or formulas or the user can write their ownbull Commercial mathematical scientific and technical applications often include converters
See also
bull Accuracy and precisionbull English unitsbull False precisionbull Imperial unitsbull International System of Unitsbull Mesures usuellesbull Metric system
bull Natural unitsbull Roundingbull Significant figuresbull Temperature conversionbull United States customary unitsbull Units conversion by factor-labelbull Units of measurement
External linksbull British law Units of measurement regulations 1995 [45]
bull ConvertBuster [46] Variety of conversion tools to convert easilybull How Many A dictionary of units of measurement [47]
bull NIST Fundamental physical constants mdash Non-SI units [48]PDF (357 KB)bull NIST Guide to SI Units [49] Many conversion factors listedbull Online Conversion Calculators [50] Very extensive list of conversions from-to equvalent unitsbull The Unified Code for Units of Measure [51]
bull Units Symbols and Conversions XML Dictionary [52]
bull Multilingual Online Conversion of Units [53]
bull Temperature Converter [54]
Conversion of units 28
References[1] United States Naval Observatory (2009) Selected Astronomical Constants 2009 (http asa usno navy mil SecK 2009
Astronomical_Constants_2009 txt) Accessed May 10 2009[2] NIST Reference on Constants Units and Uncertainty (http physics nist gov cgi-bin cuu Valuebohrrada0|search_for=Bohr+
radius)(2006) National Institute of Standards and Technology Retrieved February 22 2008[3] National Institute of Standards and Technology General Tables of Units of Measurement (http ts nist gov WeightsAndMeasures
Publications appxc cfm)[4] Lide D (Ed) (1990) Handbook of Chemistry and Physics (71st ed) Boca Raton FL CRC Press Section 1[5] National Bureau of Standards (June 30 1959) Refinement of values for the yard and the pound Federal Register viewed September 20
2006 at National Geodetic Survey web site (http www ngs noaa gov PUBS_LIB FedRegister FRdoc59-5442 pdf)[6] The International Astronomical Union and Astronomical Units (http www iau org public_press themes measuring )[7] Klein Herbert Arthur (1988) The Science of Measurement a Historical Survey Mineola NY Dover Publications 0-4862-5839-4[8] The International System of Units Section 21 (http www bipm org en si si_brochure chapter2 2-1 ) (8 ed) Bureau International des
Poids et Mesures 2006 retrieved August 26 2009[9] International System of Units (http www bipm org en si si_brochure chapter4 table8 html) 8th ed (2006) Bureau International des
Poids et Mesures Section 41 Table 8[10] P Kenneth Seidelmann Ed (1992) Explanatory Supplement to the Astronomical Almanac Sausalito CA University Science Books p 716
and sv parsec in Glossary[11] Whitelaw Ian (2007) A Measure of All Things The Story of Man and Measurement (http books google com
booksid=3zgGEWM5-iAC) New York Macmillan 0-312-37026-1 p 152[12] De Vinne Theodore Low (1900) The practice of typography a treatise on the processes of type-making the point system the names sizes
styles and prices of plain printing types (http books google com booksid=R4-DjphIpLMC) 2nd ed New York The Century Co p142ndash150
[13] Pasko Wesley Washington (1894) American dictionary of printing and bookmaking (http books google combooksid=Z_QUAAAAIAAJ) (1894) New York Howard Lockwood p 521
[14] Rowlett Russ (2005) How Many A Dictionary of Units of Measurement (http www unc edu ~rowlett units index html)[15] Thompson A and Taylor BN (2008) Guide for the Use of the International System of Units (SI) National Institute of Standards and
Technology Special Publication 811 p 57[16] US Code of Federal Regulations Title 21 Section 1019 Paragraph (b)(5)(viii) (http ecfr gpoaccess gov cgi t text text-idxc=ecframp
rgn=div8amp view=textamp node=212 0 1 1 2 1 1 6amp idno=21) retrieved August 29 2009[17] Barry N Taylor Ed NIST Special Publication 330 The International System of Units (SI) (http physics nist gov Pubs SP330 sp330
pdf) (2001 Edition) Washington US Government Printing Office 43The 12th Conference Generale des Poids et Mesures(CGPM)hellipdeclares that the word ldquolitrerdquo may be employed as a special name for the cubic decimetre
[18] CODATA Value atomic uint of mass (http physics nist gov cgi-bin cuu Valuettme|search_for=atomic+ unit+ of+ mass) (2006)National Institute of Standards and Technology Retrieved 16 September 2008
[19] The Swiss Federal Office for Metrology gives Zentner on a German language web page (http www metas ch de scales systemch html)and quintal on the English translation of that page (http www metas ch en scales systemch html) the unit is marked speacutecifiquementsuisse
[20] Pedersen O (1983) Glossary in Coyne G Hoskin M and Pedersen O Gregorian Reform of the Calendar Proceedings of the VaticanConference to Commemorate its 400th Anniversary Vatican Observatory Available from Astrophysics Data System
[21] Richards EG (1998) Mapping Time Oxford University Press pp 94ndash95 ISBN 0-19-850413-6[22] Steel Duncan (2000) Marking Time John Wiley amp Sons p 46 ISBN 0-471-29827-1[23] CODATA Value atomic unit of force (http physics nist gov cuu Constants ) (2006) National Institute of Standards and Technology
Retrieved September 14 2008[24] [[Comiteacute International des Poids et Mesures (http www bipm org en CIPM db 1946 2 )] Resolution 2] 1946 retrieved August 26
2009[25] Barry N Taylor (April 1995) Guide for the Use of the International System of Units (SI) (http physics nist gov cuu pdf sp811 pdf)
(NIST Special Publication 811) Washington DC US Government Printing Office pp 57ndash68[26] Barry N Taylor (April 1995) Guide for the Use of the International System of Units (SI) (NIST Special Publication 811) Washington DC
US Government Printing Office p 5[27] International System of Units (http www bipm org en si si_brochure chapter4 table7 html) 8th ed (2006) Bureau International des
Poids et Mesures Section 41 Table 7[28] The NIST Reference on Constants Units and Uncertainty (http physics nist gov cgi-bin cuu Valueauedm) 2006 retrieved August
26 2009[29] NIST Guide to SI Units Appendix B9 (http physics nist gov Pubs SP811 appenB9 html) retrieved August 27 2009[30] Standard for the Use of the International System of Units (SI) The Modern Metric System IEEEASTM SI 10-1997 (1997) New York and
West Conshohocken PA Institute of Electrical and Electronics Engineers and American Society for Testing and Materials Tables A1through A5
Conversion of units 29
[31] The NIST Reference on Constants Units and Uncertainty (http physics nist gov cuu Units candela html) retrieved August 28 2009[32] Ambler Thompson amp Barry N Taylor (2008) Guide for the Use of the International System of Units (SI) (http physics nist gov cuu
pdf sp811 pdf) Special Publication 811 Gaithersburg MD National Institute of Standards and Technology p 10[33] The International System of Units Section 222 Table 3 (http www bipm org en si si_brochure chapter2 2-2 table3 html) (8 ed)
Bureau International des Poids et Mesures 2006 retrieved August 27 2009[34] The NIST Guide to the SI (Special Publication 811) section 52 (http physics nist gov Pubs SP811 sec05 html5 2) 2008 retrieved
August 27 2009[35] Ambler Thompson amp Barry N Taylor (2008) Guide for the Use of the International System of Units (SI) (http physics nist gov cuu
pdf sp811 pdf) Special Publication 811 Gaithersburg MD National Institute of Standards and Technology p 5[36] [[Comiteacute international des poids et mesures (http www bipm org en CIPM db 2002 2 )] 2002 Recommendation 2] retrieved
August 27 2009[37] http converter mozdev org[38] http www xyntec com converber htm[39] http www calculla com[40] http illusions hu index phptask=100amp lang=0amp statpage=86[41] http www uniteasy com[42] http www tenderwire com wikipedialandingpage[43] http www kamlex com index phpoption=com_contentamp view=articleamp id=53amp Itemid=55[44] http www sttmedia com unitconverter[45] http www hmso gov uk si si1995 Uksi_19951804_en_2 htm[46] http www convertbuster com[47] http www unc edu ~rowlett units[48] http physics nist gov cuu Document nonsi_in_1998 pdf[49] http physics nist gov Pubs SP811 appenB9 html[50] http www onlineconversion com[51] http aurora rg iupui edu ~schadow units UCUM ucum html[52] http www posc org refs poscUnits20 xml[53] http www imperialtometric com[54] http www tampile com
Article Sources and Contributors 30
Article Sources and ContributorsConversion of units Source httpenwikipediaorgwindexphpoldid=373975089 Contributors 1571781xxx 7 A-giau AVSI Acather96 Ahoerstemeier Alexius08 Altenmann AndreEngels Andrewa Andy120290 Anonymi Ariconte Army1987 ArnoldReinhold Arthur3030 Aspects AxelBoldt AzaToth Azikala BW95 Bdesham Beland Bensaccount Bkumartvm Blackand White BlaiseFEgan BlueEarth Bobblewik Borbrav Bpmullins Bryan Derksen C J B Scholten CORNELIUSSEON CTZMSC3 Calltech Camerajohn Chaosfeary Charles MatthewsChris the speller Cmdrjameson Colonies Chris Conversion script Cope555 Crappy13 Crissov CyrilB DARTH SIDIOUS 2 DMacks DanielCD Dark Formal DarkestSideX DekisugiDenelson83 Dhp1080 Dicklyon DirkvdM Donald Duck Donarreiskoffer Dramatic Dyss DAringsbquougosz Egil Ehrenkater Ejohnsonboulder Elexmax Elf Emokhberi Enon Eob Epbr123Euchiasmus Fathead99 Father Goose Fella22 Femto FernandoAC Fibula Flutefreek Fred Bauder Fredrik Fuhghettaboutit Fuzheado Gaff Gene Nygaard Georgiy1996 Gerry AshtonGiftlite Gilliam Glenn L GoingBatty Goobergunch Gregsexton Greyengine5 Grunt Gurch Gutza HLHJ Haemo Hammersbach Heracles31 Herbee Heron HikerBush Hqb IcairnsIgiffin Indefatigable Isis JBobbitt JHunterJ Jabowery JakeVortex Jamicanmonkey Jason Begin Jay Jc3s5h Jcronen1 Jdoherty Jeffz1 Jeronimo Jimmuhk Jimp Jimwilliams57 JoeinwapJohndburger Josh Parris Jq4bagiq Kaihsu KaneWang Keenan Pepper Kevin Rector KeyStorm Khukri Kurtan Lee Daniel Crocker LightYear Linuxoidoz Liv4christ210 Loggie Lolo252Lupinelawyer M ichaeligl MJCdetroit MTC Mac MacMcF Magore Markus Kuhn Masterqwe MaxHund Maxamegalon2000 Mbeychok Meggar Mh26 Michael Daly Michael Hardy MichelAudy Mikelifeguard Mikhailov Kusserow Mindbuilder Missvain Monger Mr bulow MrOllie MrZhuKeeper Muro de Aguas Mwanner Mwtoews Nandesuka Natkeeran Ndsg NgjaimeNhy67ygv Nick Y Nick123 NickPenguin Ninjagecko Noe Nosilleg Now3r3 Obelix homologator Oldadamml Oleg Alexandrov Olivier Ortolan88 OwenBlacker Pac72 PassargeaPatrick Paul Martin Peter Horn Physchim62 Piels Pierdm Pmanderson Prometheus235 Quadell QuantumEleven Quod erat demonstrandum 314159 Radagast83 Rccoms RedWolfReinyday Revipm Rexparry sydney Reyk Rhetth Rhialto Rich Farmbrough Richard Myers Rjwilmsi Rlsheehan Robin Barry RoySmith Rpwolfgram SD6-Agent SGBailey SamuelLowry Samw Sander123 Seabhcan SebastianHelm Sherbert1 Shinhan Shrew Sietse Snel SimonP Sinbaddasail0r Skotte Smalljim SomeHuman Spencer Srleffler StarwarsmastergeekSteacoon StefanK SteveRamone Stevertigo Stokerm Suisui Sunev Superboy112233 Superm401 Synchronism Tacoman1996 Tarquin Taw Teratornis The Man in Question ThierrycThingg Thinking of England Thunderbird2 Timwi Tobias Hoevekamp Tomasr Tonsofpcs Toon05 Topsykretts2512 Trekphiler Tuwile Twanvl Uday147502 Unitman00 UrhixidurUtherSRG Vargenau Vsmith WarrenPlatts Wasell Welsh Whispering Wikinger Wolfkeeper Wtmitchell XJamRastafire Xenonice Yath Zginder Zibem Zocky Zotel 713 anonymousedits
Name of unit Symbol Definition Relation to SIunits
angular mil micro equiv 2π6400 rad asymp 0981 748 times 10minus3
rad
arcminute equiv 1deg60 asymp 0290 888 times 10minus3
rad
arcsecond equiv 1deg3600 asymp 4848 137 times 10minus6
rad
centesimal minuteof arc
equiv 1 grad100 asymp 0157 080 times 10minus3
rad
centesimal secondof arc
equiv 1 grad(10 000) asymp 1570 796 times 10minus6
rad
degree (of arc) deg equiv 1360 of a revolution equiv π180 rad asymp 17453293 times 10minus3 rad
grad gradian gon grad equiv 1400 of a revolution equiv 2π400 rad equiv 09deg asymp 15707963 times 10minus3 rad
octant equiv 45deg asymp 0785 398 rad
quadrant equiv 90deg asymp 1570 796 rad
radian (SI unit) rad The angle subtended at the center of a circle by an arc whose length is equal to the circlesradius One full revolution encompasses 2π radians
= 1 rad
sextant equiv 60deg asymp 1047 198 rad
sign equiv 30deg asymp 0523 599 rad
Conversion of units 10
Solid angle
Solid angle
Name of unit Symbol Definition Relation to SIunits
steradian (SIunit)
sr The solid angle subtended at the center of a sphere of radius r by a portion of the surface of the spherehaving an area r2 A sphere encompasses 4π sr[14]
= 1 sr
MassNotesbull See Weight for detail of massweight distinction and conversionbull In this table the unit gee is used to denote standard gravity in order to avoid confusion with the g symbol for
gramsbull In physics the pound of mass is sometimes written lbm to distinguish it from the pound-force (lbf) It should not
be read as the mongrel unit pound metre
Mass
Name of unit Symbol Definition Relation to SI units
atomic mass unit unified u AMU asymp 1660 538 73 times 10minus27 plusmn 13 times 10minus36 kg
atomic unit of mass electron restmass
me asymp 9109 382 15 times 10minus31 plusmn 45 times 10minus39 kg[18]
bag (coffee) equiv 60 kg = 60 kg
bag (Portland cement) equiv 94 lb av = 42637 682 78 kg
barge equiv 22frac12 sh tn = 20 411656 65 kg
carat kt equiv 3 16 gr asymp 205196 548 333 mg
carat (metric) ct equiv 200 mg = 200 mg
clove equiv 8 lb av = 3628 738 96 kg
crith asymp 899349 mg
dalton Da asymp 1660 902 10 times 10minus27 plusmn 13 times 10minus36 kg
dram (apothecary troy) dr t equiv 60 gr = 3887 9346 g
dram (avoirdupois) dr av equiv 27 1132 gr = 1771 845 195 3125 g
electronvolt eV equiv 1 eV (energy unit) c2 = 17826 times 10minus36 kg
gamma γ equiv 1 μg = 1 μg
grain gr equiv 17000 lb av equiv 64798 91 mg
grave G grave was the original name of the kilogram equiv 1 kg
hundredweight (long) long cwt orcwt
equiv 112 lb av = 50802 345 44 kg
hundredweight (short) cental sh cwt equiv 100 lb av = 45359 237 kg
hyl (CGS unit) equiv 1 gee times 1 g times 1 s2m = 9806 65 g
hyl (MKS unit) equiv 1 gee times 1 kg times 1 s2m = 9806 65 kg
Conversion of units 11
kilogram kg equiv mass of the prototype near Paris (asymp mass of 1L ofwater)
equiv 1 kg (SI base unit)[8]
kip kip equiv 1000 lb av = 453592 37 kg
mark equiv 8 oz t = 248827 8144 g
mite equiv 120 gr = 3239 9455 mg
mite (metric) equiv 120 g = 50 mg
ounce (apothecary troy) oz t equiv 112 lb t = 31103 4768 g
ounce (avoirdupois) oz av equiv 116 lb = 28349 523 125 g
ounce (US food nutritionlabeling)
oz equiv 28 g[16] = 28 g
pennyweight dwt pwt equiv 120 oz t = 1555 173 84 g
point equiv 1100 ct = 2 mg
pound (avoirdupois) lb av equiv 0453 592 37 kg = 7000 grains equiv 0453 592 37 kg
pound (metric) equiv 500 g = 500 g
pound (troy) lb t equiv 5 760 grains = 0373 241 7216 kg
quarter (Imperial) equiv 14 long cwt = 2 st = 28 lb av = 12700 586 36 kg
quarter (informal) equiv frac14 short tn = 226796 185 kg
quarter long (informal) equiv frac14 long tn = 254011 7272 kg
quintal (metric) q equiv 100 kg = 100 kg
scruple (apothecary) s ap equiv 20 gr = 1295 9782 g
sheet equiv 1700 lb av = 6479891 mg
slug geepound slug equiv 1 gee times 1 lb av times 1 s2ft asymp 14593 903 kg
stone st equiv 14 lb av = 6350 293 18 kg
ton assay (long) AT equiv 1 mg times 1 long tn divide 1 oz t asymp 32666 667 g
ton assay (short) AT equiv 1 mg times 1 sh tn divide 1 oz t asymp 29166 667 g
ton long long tn or ton equiv 2 240 lb = 1 016046 9088 kg
ton short sh tn equiv 2 000 lb = 907184 74 kg
tonne (mts unit) t equiv 1 000 kg = 1 000 kg
wey equiv 252 lb = 18 st = 114305 277 24 kg (variants exist)
Zentner Ztr Definitions vary see [19] and[14]
Density
Conversion of units 12
Density
Name of unit Symbol Definition Relation to SI units
gram per millilitre gmL equiv gmL = 1000 kgm3
kilogram per cubic metre (SI unit) kgm3 equiv kgm3 = 1 kgm3
slug per cubic foot slugft3 equiv slugft3 asymp 5153788184 kgm3
Time
Time t
Name of unit Symbol Definition Relation to SI units
atomic unit of time au equiv a0(αmiddotc) asymp 2418 884 254 times 10minus17
s
Callippic cycle equiv 441 mo (hollow) + 499 mo (full) = 76 a of 36525 d = 2398 3776 times 109 s
century c equiv 100 a (see below for definition of year length) = 100 times year
day d = 24 h = 86400 s
day (sidereal) d equiv Time needed for the Earth to rotate once around its axisdetermined from successive transits of a very distantastronomical object across an observers meridian(International Celestial Reference Frame)
asymp 86 1641 s
decade dec equiv 10 a (see below for definition of year length) = 10 times year
fortnight fn equiv 2 wk = 1 209 600 s
helek equiv 11 080 h = 33 s
Hipparchic cycle equiv 4 Callippic cycles - 1 d = 9593 424 times 109 s
hour h equiv 60 min = 3 600 s
jiffy j equiv 160 s = 016 s
jiffy (alternate) ja equiv 1100 s = 10 ms
ke (quarter of an hour) equiv frac14 h = 196 d = 60 times 60 4 s = 900 s= 60 4 min = 15 min
Conversion of units 13
ke (traditional) equiv 1100 d = 24 times 60 times 60 100 s =864 s = 24 60 100min = 144 min
lustre lustrum equiv 5 a of 365 d = 15768 times 108 s
Metonic cycle enneadecaeteris equiv 110 mo (hollow) + 125 mo (full) = 6940 d asymp 19 a = 5996 16 times 108 s
millennium equiv 1 000 a (see below for definition of year length) = 1000 times year
milliday md equiv 11 000 d = 24 times 60 times 60 1 000 s= 864 s
minute min equiv 60 s due to leap seconds sometimes 59 s or 61 s = 60 s
moment equiv 90 s = 90 s
month (full) mo equiv 30 d[20] = 2 592 000 s
month (Greg av) mo Average Gregorian month = 365242512 d = 30436875 d asymp 26297 times 106 s
month (hollow) mo equiv 29 d[20] = 2 505 600 s
month (synodic) mo Cycle time of moon phases asymp 29530589 days (Average) asymp 2551 times 106 s
octaeteris = 48 mo (full) + 48 mo (hollow) + 3 mo (full)[21] [22] = 8 aof 36525 d = 2922 d
= 2524 608 times 108 s
Planck time equiv (Gℏc5)frac12 asymp 1351 211 868 times 10minus43
s
second s time of 9 192 631 770 periods of the radiation correspondingto the transition between the 2 hyperfine levels of the groundstate of the caesium 133 atom at 0 K[8] (but other secondsare sometimes used in astronomy)
(SI base unit)
shake equiv 10minus8 s = 10 ns
sigma equiv 10minus6 s = 1 μs
Sothic cycle equiv 1 461 a of 365 d = 4607 4096 times 1010 s
svedberg S equiv 10minus13 s = 100 fs
week wk equiv 7 d = 604 800 s
year (Gregorian) a y oryr
= 3652425 d average calculated from common years (365d) plus leap years (366 d) on most years divisible by 4 Seeleap year for details
= 31 556 952 s
year (Julian) a y oryr
= 36525 d average calculated from common years (365 d)plus one leap year (366 d) every four years
= 31 557 600 s
year (sidereal) a y oryr
equiv time taken for Sun to return to the same position withrespect to the stars of the celestial sphere
asymp 365256 363 d asymp 31558 1497632 s
year (tropical) a y oryr
equiv Length of time it takes for the Sun to return to the sameposition in the cycle of seasons
asymp 365242 190 d asymp 31556 925 s
Where UTC is observed the length of timeunits longer than 1 s may increase or decreaseby 1 s if a leap second occurs during the timeinterval of interest
Conversion of units 14
Frequency
Frequency
Name of unit Symbol Definition Relation to SI units
hertz (SI unit) Hz equiv Number of cycles per second = 1 Hz = 1s
revolutions per minute rpm equiv One unit rpm equals one rotation completed around a fixed axis in one minute of time asymp0104719755 rads
Speed or velocity
Speed
Name of unit Symbol Definition Relation to SI units
foot per hour fph equiv 1 fth asymp 8466 667 times 10minus5
ms
foot per minute fpm equiv 1 ftmin = 508 times 10minus3 ms
foot per second fps equiv 1 fts = 3048 times 10minus1 ms
furlong perfortnight
equiv furlongfortnight asymp 1663 095 times 10minus4
ms
inch per minute ipm equiv 1 inmin asymp 423 333 times 10minus4 ms
inch per second ips equiv 1 ins = 254 times 10minus2 ms
mach number M Ratio of the speed to the speed of sound in the medium Varies especially with temperatureAbout 761 mph (1225 kph) in air at sea level to about 660 mph (1062 kph) at jet altitudesUnitless
asymp 340 to 295 ms foraircraft
metre per second(SI unit)
ms equiv 1 ms = 1 ms
mile per hour mph equiv 1 mih = 0447 04 ms
mile per minute mpm equiv 1 mimin = 268224 ms
mile per second mps equiv 1 mis = 1 609344 ms
speed of light invacuum
c equiv 299 792 458 ms = 299 792 458 ms
speed of sound inair
s Varies especially with temperature About 761 mph (1225 kph) in air at sea level to about660 mph (1062 kph) at jet altitudes
asymp 340 to 295 ms ataircraft altitudes
A velocity consists of a speed combined with a direction the speed part of the velocity takes units of speed
Conversion of units 15
Flow (volume)
Flow
Name of unit Symbol Definition Relation to SI units
cubic foot per minute CFM equiv 1 ft3min = 4719474432 times 10minus4 m3s
cubic foot per second ft3s equiv 1 ft3s = 0028316846592 m3s
cubic inch per minute in3min equiv 1 in3min = 27311773 times 10minus7 m3s
cubic inch per second in3s equiv 1 in3s = 16387064 times 10minus5 m3s
cubic metre per second (SIunit)
m3s equiv 1 m3s = 1 m3s
gallon (US fluid) per day GPD equiv 1 gald = 4381263638 times 10minus8 m3s
gallon (US fluid) per hour GPH equiv 1 galh = 1051503273 times 10minus6 m3s
gallon (US fluid) per minute GPM equiv 1 galmin = 630901964 times 10minus5 m3s
litre per minute LPM equiv 1 Lmin = 16 times 10minus5 m3s
Acceleration
Acceleration
Name of unit Symbol Definition Relation to SI units
foot per hour per second fphs equiv 1 ft(hmiddots) asymp 8466 667 times 10minus5
ms2
foot per minute per second fpms equiv 1 ft(minmiddots) = 508 times 10minus3 ms2
foot per second squared fps2 equiv 1 fts2 = 3048 times 10minus1 ms2
gal galileo Gal equiv 1 cms2 = 10minus2 ms2
inch per minute per second ipms equiv 1 in(minmiddots) asymp 4233 333 times 10minus4
ms2
inch per second squared ips2 equiv 1 ins2 = 254 times 10minus2 ms2
knot per second kns equiv 1 kns asymp 5144 444 times 10minus1
ms2
metre per second squared (SI unit) ms2 equiv 1 ms2 = 1 ms2
mile per hour per second mphs equiv 1 mi(hmiddots) = 44704 times 10minus1 ms2
mile per minute per second mpms equiv 1 mi(minmiddots) = 268224 ms2
mile per second squared mps2 equiv 1 mis2 = 1609 344 times 103 ms2
standard gravity g equiv 9806 65 ms2 = 9806 65 ms2
Conversion of units 16
Force
Force
Name of unit Symbol Definition Relation to SI units
atomic unit of force equiv memiddotα2middotc2a0 asymp 8238 722 06 times 10minus8 N
[23]
dyne (cgs unit) dyn equiv gmiddotcms2 = 10minus5 N
kilogram-force kilopondgrave-force
kgf kp Gf equiv g times 1 kg = 9806 65 N
kip kip-force kip kipfklbf
equiv g times 1 000 lb = 4448 221 6152605 times 103 N
milligrave-force gravet-force mGf gf equiv g times 1 g = 9806 65 mN
newton (SI unit) N A force capable of giving a mass of one kg an acceleration of one metreper second per second[24]
= 1 N = 1 kgmiddotms2
ounce-force ozf equiv g times 1 oz = 0278 013 850 9537812 N
pound lb equiv slugmiddotfts2 = 4448 230 531 N
pound-force lbf equiv g times 1 lb = 4448 221 615 2605 N
poise (cgs unit) P equiv 10minus1 Pamiddots = 01 Pamiddots
pound per foot hour lb(ftmiddoth) equiv 1 lb(ftmiddoth) asymp 4133 789 times 10minus4 Pamiddots
pound per foot second lb(ftmiddots) equiv 1 lb(ftmiddots) asymp 1488164 Pamiddots
pound-force second per square foot lbfmiddotsft2 equiv 1 lbfmiddotsft2 asymp 4788026 Pamiddots
pound-force second per square inch lbfmiddotsin2 equiv 1 lbfmiddotsin2 asymp 6894757 Pamiddots
Conversion of units 21
Kinematic viscosity
Kinematic viscosity
Name of unit Symbol Definition Relation to SI units
square foot per second ft2s equiv 1 ft2s = 009290304 m2s
square metre per second (SI unit) m2s equiv 1 m2s = 1 m2s
stokes (cgs unit) St equiv10minus4 m2s
= 10minus4 m2s
Electric current
Electric current
Name of unit Symbol Definition Relation to SI units
ampere (SI base unit) A equiv The constant current needed to produce a force of 2 times 10minus7 newton per metre betweentwo straight parallel conductors of infinite length and negligible circular cross-sectionplaced one metre apart in a vacuum[8]
= 1 A
electromagnetic unitabampere (cgs unit)
abamp equiv 10 A = 10 A
esu per secondstatampere (cgs unit)
esus equiv (01 Amiddotms) c asymp3335641 times 10minus10 A
Electric charge
Electric charge
Name of unit Symbol Definition Relation to SI units
abcoulomb electromagnetic unit (cgsunit)
abC emu equiv 10 C = 10 C
atomic unit of charge au equiv e asymp 1602 176462 times 10minus19 C
coulomb (SI unit) C equiv The amount of electricity carried in one second of time by oneampere of current[24]
= 1 C = 1 Amiddots
faraday F equiv 1 mol times NAmiddote asymp 96 4853383 C
statcoulomb franklin electrostatic unit(cgs unit)
statC Fresu
equiv (01 Amiddotm) c asymp 3335 641 times 10minus10 C
Conversion of units 22
Electric dipole
Electric dipole
Name of unit Symbol Definition Relation to SI units
atomic unit of electric dipole moment ea0 asymp 8478 352 81 times 10minus30
Cmiddotm[28]
Electromotive force electric potential difference
Voltage electromotive force
Name ofunit
Symbol Definition Relation to SI units
abvolt (cgsunit)
abV equiv 1 times 10minus8 V = 1 times 10minus8 V
statvolt (cgsunit)
statV equiv cmiddot (1 μJAmiddotm) = 299792 458 V
volt (SIunit)
V The difference in electric potential across two points along a conducting wire carrying one ampereof constant current when the power dissipated between the points equals one watt[24]
= 1 V = 1 WA = 1kgmiddotm2(Amiddots3)
Electrical resistance
Electrical resistance
Name ofunit
Symbol Definition Relation to SI units
ohm (SIunit)
Ω The resistance between two points in a conductor when one volt of electric potential differenceapplied to these points produces one ampere of current in the conductor[24]
= 1 Ω = 1 VA = 1kgmiddotm2(A2middots3)
Capacitance
Capacitors ability to store charge
Name ofunit
Symbol Definition Relation to SI units
farad (SIunit)
F The capacitance between two parallel plates that results in one volt of potential difference whencharged by one coulomb of electricity[24]
= 1 F = 1 CV = 1A2middots4(kgmiddotm2)
Conversion of units 23
Magnetic flux
magnetic flux
Name of unit Symbol Definition Relation to SI units
maxwell (CGSunit)
Mx equiv 10minus8 Wb[29] = 1 times 10minus8 Wb
weber (SIunit)
Wb Magnetic flux which linking a circuit of one turn would produce in it an electromotive force of1 volt if it were reduced to zero at a uniform rate in 1 second[24]
= 1 Wb = 1 Vmiddots = 1kgmiddotm2(Amiddots2)
Magnetic flux density
What physicists call Magnetic field is called Magnetic flux density by electrical engineersand magnetic induction by applied mathematicians and electrical engineers
Name of unit Symbol Definition Relation to SI units
gauss (CGS unit) G equiv Mxcm2 = 10minus4
T= 1 times 10minus4 T [30]
tesla (SI unit) T equiv Wbm2 = 1 T = 1 Wbm2 = 1kg(Amiddots2)
Inductance
Inductance
Name ofunit
Symbol Definition Relation to SI units
henry (SIunit)
H The inductance of a closed circuit that produces one volt of electromotive force when the current inthe circuit varies at a uniform rate of one ampere per second[24]
= 1 H = 1 WbA = 1kgmiddotm2(Amiddots)2
Temperature
Temperature
Name of unit Symbol Definition Conversion to kelvin
degree Celsius degC degC equiv K minus 27315 [K] equiv [degC] + 27315
degree Delisle degDe [K] = 37315 minus [degDe] times 23
degree Fahrenheit degF degF equiv degC times 95 + 32 [K] equiv ([degF] + 45967) times 59
degree Newton degN [K] = [degN] times 10033 + 27315
degree Rankine degR degRa degR equiv K times 95 [K] equiv [degR] times 59
degree Reacuteaumur degReacute [K] = [degReacute] times 54 + 27315
degree Roslashmer degRoslash [K] = ([degRoslash] minus 75) times 4021 + 27315
kelvin (SI baseunit)
K equiv 127316 of the thermodynamic temperature of the triple point of water[8] equiv 1 K
Conversion of units 24
Information entropy
Information entropy
Name of unit Symbol Definition Relation to SI units Relation to bits
SI unit JK equiv JK = 1 JK
nat nip nepit nat equiv kB = 1380 650 5(23) times 10minus23 JK
bit shannon bit b Sh equiv ln(2) times kB = 9569 940 (16) times 10minus24 JK = 1 bit
ban hartley ban Hart equiv ln(10) times kB = 3179 065 3(53) times 10minus23 JK
nibble equiv 4 bits = 3827 976 0(64) times 10minus23 JK = 22 bit
byte B equiv 8 bits = 7655 952 (13) times 10minus23 JK = 23 bit
kilobyte (decimal) kB equiv 1 000 B = 7655 952 (13) times 10minus20 JK
kilobyte (kibibyte) KB KiB equiv 1 024 B = 7839 695 (13) times 10minus20 JK = 210 bit
Often information entropy is measured in shannons whereas the (discrete) storage space of digital devices ismeasured in bits Thus uncompressed redundant data occupy more than one bit of storage per shannon ofinformation entropy The multiples of a bit listed above are usually used with this meaning Other times the bit isused as a measure of information entropy and is thus a synonym of shannon
Luminous intensityThe candela is the preferred nomenclature for the SI unit
Luminous intensity
Name of unit Symbol Definition Relation toSI units
candela (SI baseunit) candle
cd The luminous intensity in a given direction of a source that emits monochromatic radiation offrequency 540 times 1012 hertz and that has a radiant intensity in that direction of 1683 watt persteradian[8]
= 1 cd
candlepower (new) cp equiv cd The use of candlepower as a unit is discouraged due to its ambiguity = 1 cd
candlepower (oldpre-1948)
cp Varies and is poorly reproducible[31] Approximately 0981 cd[14] asymp 0981 cd
Luminance
Conversion of units 25
Luminance
Name of unit Symbol Definition Relation to SI units
candela per square foot cdft2 equiv cdft2 asymp10763910417 cdm2
candela per square inch cdin2 equiv cdin2 asymp 15500031 cdm2
candela per square metre (SI unit) nit (deprecated[14] ) cdm2 equiv cdm2 = 1 cdm2
Name of unit Symbol Definition Relation to SI units
lumen (SIunit)
lm equiv cdmiddotsr = 1 lm = 1 cdmiddotsr
Illuminance
Illuminance
Name of unit Symbol Definition Relation to SI units
footcandle lumen per square foot fc equiv lmft2 = 10763910417 lx
lumen per square inch lmin2 equiv lmin2 asymp 15500031 lx
lux (SI unit) lx equiv lmm2 = 1 lx = 1 lmm2
phot (CGS unit) ph equiv lmcm2 = 1 times 104 lx
Radiation - source activity
Conversion of units 26
Radioactivity
Name of unit Symbol Definition Relation to SI units
becquerel (SIunit)
Bq equiv Number of disintegrations per second = 1 Bq = 1s
curie Ci equiv 37 times 1010 Bq = 37 times 1010 Bq [32]
rutherford (H) rd equiv 1 MBq = 1 times 106 Bq
Please note that although becquerel (Bq) and hertz (Hz) both ultimately refer to the same SI base unit (sminus1) Hz isused only for periodic phenomena and Bq is only used for stochastic processes associated with radioactivity[33]
Radiation - exposure
Radiation - exposure
Name of unit Symbol Definition Relation to SI units
roentgen R 1 R equiv 258 times 10minus4 Ckg[29] = 258 times 10minus4 Ckg
The roentgen is not a SI unit and the NIST strongly discourages its continued use[34]
Radiation - absorbed dose
Radiation - absorbed dose
Name of unit Symbol Definition Relation to SI units
Name of unit Symbol Definition Relation to SI units
Roumlntgen equivalent man rem equiv 001 Sv = 001 Sv
sievert (SI unit) Sv equiv 1 Jkg[33] = 1 Sv
Although the definitions for sievert (Sv) and gray (Gy) would seem to indicate that they measure the same quantitiesthis is not the case The effect of receiving a certain dose of radiation (given as Gy) is variable and depends on manyfactors thus a new unit was needed to denote the biological effectiveness of that dose on the body this is known asthe equivalent dose and is shown in Sv The general relationship between absorbed dose and equivalent dose can berepresented as
H = Q middot D
where H is the equivalent dose D is the absorbed dose and Q is a dimensionless quality factor Thus for anyquantity of D measured in Gy the numerical value for H measured in Sv may be different[36]
Conversion of units 27
Software toolsHome and office computers come with converters in bundled spreadsheet applications or can access free convertersvia the Internet Units and measurements can be easily converted using these tools but only if the units are explicitlydefined and the conversion is compatible (eg cmHg to kPa)
Free conversion softwarebull Units (software) a popular cross-platform command-line utilitybull Converter [37] contextual unit converter for Mozilla Firefox browsersbull Converber [38] portable application converting utilitybull calculla [39] calculla - online web convertersbull iMetrix [40] - unit converter for xpbull uniteasy [41] online scientific unit conversionbull Unit Converter Add-in for Excel [42] - allow a large selection of unit conversions within the Microsoft Excel
spread sheet programbull Unit Converter [43] simple and extensible unit converterbull Portable Unit Converter [44] including 4500 units 33 unit-categories and the possibility to create custom units
General commercial sources of convertersbull Advanced electronic calculators have unit-conversion functionalitybull Spreadsheet programs usually provide conversion functions or formulas or the user can write their ownbull Commercial mathematical scientific and technical applications often include converters
See also
bull Accuracy and precisionbull English unitsbull False precisionbull Imperial unitsbull International System of Unitsbull Mesures usuellesbull Metric system
bull Natural unitsbull Roundingbull Significant figuresbull Temperature conversionbull United States customary unitsbull Units conversion by factor-labelbull Units of measurement
External linksbull British law Units of measurement regulations 1995 [45]
bull ConvertBuster [46] Variety of conversion tools to convert easilybull How Many A dictionary of units of measurement [47]
bull NIST Fundamental physical constants mdash Non-SI units [48]PDF (357 KB)bull NIST Guide to SI Units [49] Many conversion factors listedbull Online Conversion Calculators [50] Very extensive list of conversions from-to equvalent unitsbull The Unified Code for Units of Measure [51]
bull Units Symbols and Conversions XML Dictionary [52]
bull Multilingual Online Conversion of Units [53]
bull Temperature Converter [54]
Conversion of units 28
References[1] United States Naval Observatory (2009) Selected Astronomical Constants 2009 (http asa usno navy mil SecK 2009
Astronomical_Constants_2009 txt) Accessed May 10 2009[2] NIST Reference on Constants Units and Uncertainty (http physics nist gov cgi-bin cuu Valuebohrrada0|search_for=Bohr+
radius)(2006) National Institute of Standards and Technology Retrieved February 22 2008[3] National Institute of Standards and Technology General Tables of Units of Measurement (http ts nist gov WeightsAndMeasures
Publications appxc cfm)[4] Lide D (Ed) (1990) Handbook of Chemistry and Physics (71st ed) Boca Raton FL CRC Press Section 1[5] National Bureau of Standards (June 30 1959) Refinement of values for the yard and the pound Federal Register viewed September 20
2006 at National Geodetic Survey web site (http www ngs noaa gov PUBS_LIB FedRegister FRdoc59-5442 pdf)[6] The International Astronomical Union and Astronomical Units (http www iau org public_press themes measuring )[7] Klein Herbert Arthur (1988) The Science of Measurement a Historical Survey Mineola NY Dover Publications 0-4862-5839-4[8] The International System of Units Section 21 (http www bipm org en si si_brochure chapter2 2-1 ) (8 ed) Bureau International des
Poids et Mesures 2006 retrieved August 26 2009[9] International System of Units (http www bipm org en si si_brochure chapter4 table8 html) 8th ed (2006) Bureau International des
Poids et Mesures Section 41 Table 8[10] P Kenneth Seidelmann Ed (1992) Explanatory Supplement to the Astronomical Almanac Sausalito CA University Science Books p 716
and sv parsec in Glossary[11] Whitelaw Ian (2007) A Measure of All Things The Story of Man and Measurement (http books google com
booksid=3zgGEWM5-iAC) New York Macmillan 0-312-37026-1 p 152[12] De Vinne Theodore Low (1900) The practice of typography a treatise on the processes of type-making the point system the names sizes
styles and prices of plain printing types (http books google com booksid=R4-DjphIpLMC) 2nd ed New York The Century Co p142ndash150
[13] Pasko Wesley Washington (1894) American dictionary of printing and bookmaking (http books google combooksid=Z_QUAAAAIAAJ) (1894) New York Howard Lockwood p 521
[14] Rowlett Russ (2005) How Many A Dictionary of Units of Measurement (http www unc edu ~rowlett units index html)[15] Thompson A and Taylor BN (2008) Guide for the Use of the International System of Units (SI) National Institute of Standards and
Technology Special Publication 811 p 57[16] US Code of Federal Regulations Title 21 Section 1019 Paragraph (b)(5)(viii) (http ecfr gpoaccess gov cgi t text text-idxc=ecframp
rgn=div8amp view=textamp node=212 0 1 1 2 1 1 6amp idno=21) retrieved August 29 2009[17] Barry N Taylor Ed NIST Special Publication 330 The International System of Units (SI) (http physics nist gov Pubs SP330 sp330
pdf) (2001 Edition) Washington US Government Printing Office 43The 12th Conference Generale des Poids et Mesures(CGPM)hellipdeclares that the word ldquolitrerdquo may be employed as a special name for the cubic decimetre
[18] CODATA Value atomic uint of mass (http physics nist gov cgi-bin cuu Valuettme|search_for=atomic+ unit+ of+ mass) (2006)National Institute of Standards and Technology Retrieved 16 September 2008
[19] The Swiss Federal Office for Metrology gives Zentner on a German language web page (http www metas ch de scales systemch html)and quintal on the English translation of that page (http www metas ch en scales systemch html) the unit is marked speacutecifiquementsuisse
[20] Pedersen O (1983) Glossary in Coyne G Hoskin M and Pedersen O Gregorian Reform of the Calendar Proceedings of the VaticanConference to Commemorate its 400th Anniversary Vatican Observatory Available from Astrophysics Data System
[21] Richards EG (1998) Mapping Time Oxford University Press pp 94ndash95 ISBN 0-19-850413-6[22] Steel Duncan (2000) Marking Time John Wiley amp Sons p 46 ISBN 0-471-29827-1[23] CODATA Value atomic unit of force (http physics nist gov cuu Constants ) (2006) National Institute of Standards and Technology
Retrieved September 14 2008[24] [[Comiteacute International des Poids et Mesures (http www bipm org en CIPM db 1946 2 )] Resolution 2] 1946 retrieved August 26
2009[25] Barry N Taylor (April 1995) Guide for the Use of the International System of Units (SI) (http physics nist gov cuu pdf sp811 pdf)
(NIST Special Publication 811) Washington DC US Government Printing Office pp 57ndash68[26] Barry N Taylor (April 1995) Guide for the Use of the International System of Units (SI) (NIST Special Publication 811) Washington DC
US Government Printing Office p 5[27] International System of Units (http www bipm org en si si_brochure chapter4 table7 html) 8th ed (2006) Bureau International des
Poids et Mesures Section 41 Table 7[28] The NIST Reference on Constants Units and Uncertainty (http physics nist gov cgi-bin cuu Valueauedm) 2006 retrieved August
26 2009[29] NIST Guide to SI Units Appendix B9 (http physics nist gov Pubs SP811 appenB9 html) retrieved August 27 2009[30] Standard for the Use of the International System of Units (SI) The Modern Metric System IEEEASTM SI 10-1997 (1997) New York and
West Conshohocken PA Institute of Electrical and Electronics Engineers and American Society for Testing and Materials Tables A1through A5
Conversion of units 29
[31] The NIST Reference on Constants Units and Uncertainty (http physics nist gov cuu Units candela html) retrieved August 28 2009[32] Ambler Thompson amp Barry N Taylor (2008) Guide for the Use of the International System of Units (SI) (http physics nist gov cuu
pdf sp811 pdf) Special Publication 811 Gaithersburg MD National Institute of Standards and Technology p 10[33] The International System of Units Section 222 Table 3 (http www bipm org en si si_brochure chapter2 2-2 table3 html) (8 ed)
Bureau International des Poids et Mesures 2006 retrieved August 27 2009[34] The NIST Guide to the SI (Special Publication 811) section 52 (http physics nist gov Pubs SP811 sec05 html5 2) 2008 retrieved
August 27 2009[35] Ambler Thompson amp Barry N Taylor (2008) Guide for the Use of the International System of Units (SI) (http physics nist gov cuu
pdf sp811 pdf) Special Publication 811 Gaithersburg MD National Institute of Standards and Technology p 5[36] [[Comiteacute international des poids et mesures (http www bipm org en CIPM db 2002 2 )] 2002 Recommendation 2] retrieved
August 27 2009[37] http converter mozdev org[38] http www xyntec com converber htm[39] http www calculla com[40] http illusions hu index phptask=100amp lang=0amp statpage=86[41] http www uniteasy com[42] http www tenderwire com wikipedialandingpage[43] http www kamlex com index phpoption=com_contentamp view=articleamp id=53amp Itemid=55[44] http www sttmedia com unitconverter[45] http www hmso gov uk si si1995 Uksi_19951804_en_2 htm[46] http www convertbuster com[47] http www unc edu ~rowlett units[48] http physics nist gov cuu Document nonsi_in_1998 pdf[49] http physics nist gov Pubs SP811 appenB9 html[50] http www onlineconversion com[51] http aurora rg iupui edu ~schadow units UCUM ucum html[52] http www posc org refs poscUnits20 xml[53] http www imperialtometric com[54] http www tampile com
Article Sources and Contributors 30
Article Sources and ContributorsConversion of units Source httpenwikipediaorgwindexphpoldid=373975089 Contributors 1571781xxx 7 A-giau AVSI Acather96 Ahoerstemeier Alexius08 Altenmann AndreEngels Andrewa Andy120290 Anonymi Ariconte Army1987 ArnoldReinhold Arthur3030 Aspects AxelBoldt AzaToth Azikala BW95 Bdesham Beland Bensaccount Bkumartvm Blackand White BlaiseFEgan BlueEarth Bobblewik Borbrav Bpmullins Bryan Derksen C J B Scholten CORNELIUSSEON CTZMSC3 Calltech Camerajohn Chaosfeary Charles MatthewsChris the speller Cmdrjameson Colonies Chris Conversion script Cope555 Crappy13 Crissov CyrilB DARTH SIDIOUS 2 DMacks DanielCD Dark Formal DarkestSideX DekisugiDenelson83 Dhp1080 Dicklyon DirkvdM Donald Duck Donarreiskoffer Dramatic Dyss DAringsbquougosz Egil Ehrenkater Ejohnsonboulder Elexmax Elf Emokhberi Enon Eob Epbr123Euchiasmus Fathead99 Father Goose Fella22 Femto FernandoAC Fibula Flutefreek Fred Bauder Fredrik Fuhghettaboutit Fuzheado Gaff Gene Nygaard Georgiy1996 Gerry AshtonGiftlite Gilliam Glenn L GoingBatty Goobergunch Gregsexton Greyengine5 Grunt Gurch Gutza HLHJ Haemo Hammersbach Heracles31 Herbee Heron HikerBush Hqb IcairnsIgiffin Indefatigable Isis JBobbitt JHunterJ Jabowery JakeVortex Jamicanmonkey Jason Begin Jay Jc3s5h Jcronen1 Jdoherty Jeffz1 Jeronimo Jimmuhk Jimp Jimwilliams57 JoeinwapJohndburger Josh Parris Jq4bagiq Kaihsu KaneWang Keenan Pepper Kevin Rector KeyStorm Khukri Kurtan Lee Daniel Crocker LightYear Linuxoidoz Liv4christ210 Loggie Lolo252Lupinelawyer M ichaeligl MJCdetroit MTC Mac MacMcF Magore Markus Kuhn Masterqwe MaxHund Maxamegalon2000 Mbeychok Meggar Mh26 Michael Daly Michael Hardy MichelAudy Mikelifeguard Mikhailov Kusserow Mindbuilder Missvain Monger Mr bulow MrOllie MrZhuKeeper Muro de Aguas Mwanner Mwtoews Nandesuka Natkeeran Ndsg NgjaimeNhy67ygv Nick Y Nick123 NickPenguin Ninjagecko Noe Nosilleg Now3r3 Obelix homologator Oldadamml Oleg Alexandrov Olivier Ortolan88 OwenBlacker Pac72 PassargeaPatrick Paul Martin Peter Horn Physchim62 Piels Pierdm Pmanderson Prometheus235 Quadell QuantumEleven Quod erat demonstrandum 314159 Radagast83 Rccoms RedWolfReinyday Revipm Rexparry sydney Reyk Rhetth Rhialto Rich Farmbrough Richard Myers Rjwilmsi Rlsheehan Robin Barry RoySmith Rpwolfgram SD6-Agent SGBailey SamuelLowry Samw Sander123 Seabhcan SebastianHelm Sherbert1 Shinhan Shrew Sietse Snel SimonP Sinbaddasail0r Skotte Smalljim SomeHuman Spencer Srleffler StarwarsmastergeekSteacoon StefanK SteveRamone Stevertigo Stokerm Suisui Sunev Superboy112233 Superm401 Synchronism Tacoman1996 Tarquin Taw Teratornis The Man in Question ThierrycThingg Thinking of England Thunderbird2 Timwi Tobias Hoevekamp Tomasr Tonsofpcs Toon05 Topsykretts2512 Trekphiler Tuwile Twanvl Uday147502 Unitman00 UrhixidurUtherSRG Vargenau Vsmith WarrenPlatts Wasell Welsh Whispering Wikinger Wolfkeeper Wtmitchell XJamRastafire Xenonice Yath Zginder Zibem Zocky Zotel 713 anonymousedits
Name of unit Symbol Definition Relation to SIunits
angular mil micro equiv 2π6400 rad asymp 0981 748 times 10minus3
rad
arcminute equiv 1deg60 asymp 0290 888 times 10minus3
rad
arcsecond equiv 1deg3600 asymp 4848 137 times 10minus6
rad
centesimal minuteof arc
equiv 1 grad100 asymp 0157 080 times 10minus3
rad
centesimal secondof arc
equiv 1 grad(10 000) asymp 1570 796 times 10minus6
rad
degree (of arc) deg equiv 1360 of a revolution equiv π180 rad asymp 17453293 times 10minus3 rad
grad gradian gon grad equiv 1400 of a revolution equiv 2π400 rad equiv 09deg asymp 15707963 times 10minus3 rad
octant equiv 45deg asymp 0785 398 rad
quadrant equiv 90deg asymp 1570 796 rad
radian (SI unit) rad The angle subtended at the center of a circle by an arc whose length is equal to the circlesradius One full revolution encompasses 2π radians
= 1 rad
sextant equiv 60deg asymp 1047 198 rad
sign equiv 30deg asymp 0523 599 rad
Conversion of units 10
Solid angle
Solid angle
Name of unit Symbol Definition Relation to SIunits
steradian (SIunit)
sr The solid angle subtended at the center of a sphere of radius r by a portion of the surface of the spherehaving an area r2 A sphere encompasses 4π sr[14]
= 1 sr
MassNotesbull See Weight for detail of massweight distinction and conversionbull In this table the unit gee is used to denote standard gravity in order to avoid confusion with the g symbol for
gramsbull In physics the pound of mass is sometimes written lbm to distinguish it from the pound-force (lbf) It should not
be read as the mongrel unit pound metre
Mass
Name of unit Symbol Definition Relation to SI units
atomic mass unit unified u AMU asymp 1660 538 73 times 10minus27 plusmn 13 times 10minus36 kg
atomic unit of mass electron restmass
me asymp 9109 382 15 times 10minus31 plusmn 45 times 10minus39 kg[18]
bag (coffee) equiv 60 kg = 60 kg
bag (Portland cement) equiv 94 lb av = 42637 682 78 kg
barge equiv 22frac12 sh tn = 20 411656 65 kg
carat kt equiv 3 16 gr asymp 205196 548 333 mg
carat (metric) ct equiv 200 mg = 200 mg
clove equiv 8 lb av = 3628 738 96 kg
crith asymp 899349 mg
dalton Da asymp 1660 902 10 times 10minus27 plusmn 13 times 10minus36 kg
dram (apothecary troy) dr t equiv 60 gr = 3887 9346 g
dram (avoirdupois) dr av equiv 27 1132 gr = 1771 845 195 3125 g
electronvolt eV equiv 1 eV (energy unit) c2 = 17826 times 10minus36 kg
gamma γ equiv 1 μg = 1 μg
grain gr equiv 17000 lb av equiv 64798 91 mg
grave G grave was the original name of the kilogram equiv 1 kg
hundredweight (long) long cwt orcwt
equiv 112 lb av = 50802 345 44 kg
hundredweight (short) cental sh cwt equiv 100 lb av = 45359 237 kg
hyl (CGS unit) equiv 1 gee times 1 g times 1 s2m = 9806 65 g
hyl (MKS unit) equiv 1 gee times 1 kg times 1 s2m = 9806 65 kg
Conversion of units 11
kilogram kg equiv mass of the prototype near Paris (asymp mass of 1L ofwater)
equiv 1 kg (SI base unit)[8]
kip kip equiv 1000 lb av = 453592 37 kg
mark equiv 8 oz t = 248827 8144 g
mite equiv 120 gr = 3239 9455 mg
mite (metric) equiv 120 g = 50 mg
ounce (apothecary troy) oz t equiv 112 lb t = 31103 4768 g
ounce (avoirdupois) oz av equiv 116 lb = 28349 523 125 g
ounce (US food nutritionlabeling)
oz equiv 28 g[16] = 28 g
pennyweight dwt pwt equiv 120 oz t = 1555 173 84 g
point equiv 1100 ct = 2 mg
pound (avoirdupois) lb av equiv 0453 592 37 kg = 7000 grains equiv 0453 592 37 kg
pound (metric) equiv 500 g = 500 g
pound (troy) lb t equiv 5 760 grains = 0373 241 7216 kg
quarter (Imperial) equiv 14 long cwt = 2 st = 28 lb av = 12700 586 36 kg
quarter (informal) equiv frac14 short tn = 226796 185 kg
quarter long (informal) equiv frac14 long tn = 254011 7272 kg
quintal (metric) q equiv 100 kg = 100 kg
scruple (apothecary) s ap equiv 20 gr = 1295 9782 g
sheet equiv 1700 lb av = 6479891 mg
slug geepound slug equiv 1 gee times 1 lb av times 1 s2ft asymp 14593 903 kg
stone st equiv 14 lb av = 6350 293 18 kg
ton assay (long) AT equiv 1 mg times 1 long tn divide 1 oz t asymp 32666 667 g
ton assay (short) AT equiv 1 mg times 1 sh tn divide 1 oz t asymp 29166 667 g
ton long long tn or ton equiv 2 240 lb = 1 016046 9088 kg
ton short sh tn equiv 2 000 lb = 907184 74 kg
tonne (mts unit) t equiv 1 000 kg = 1 000 kg
wey equiv 252 lb = 18 st = 114305 277 24 kg (variants exist)
Zentner Ztr Definitions vary see [19] and[14]
Density
Conversion of units 12
Density
Name of unit Symbol Definition Relation to SI units
gram per millilitre gmL equiv gmL = 1000 kgm3
kilogram per cubic metre (SI unit) kgm3 equiv kgm3 = 1 kgm3
slug per cubic foot slugft3 equiv slugft3 asymp 5153788184 kgm3
Time
Time t
Name of unit Symbol Definition Relation to SI units
atomic unit of time au equiv a0(αmiddotc) asymp 2418 884 254 times 10minus17
s
Callippic cycle equiv 441 mo (hollow) + 499 mo (full) = 76 a of 36525 d = 2398 3776 times 109 s
century c equiv 100 a (see below for definition of year length) = 100 times year
day d = 24 h = 86400 s
day (sidereal) d equiv Time needed for the Earth to rotate once around its axisdetermined from successive transits of a very distantastronomical object across an observers meridian(International Celestial Reference Frame)
asymp 86 1641 s
decade dec equiv 10 a (see below for definition of year length) = 10 times year
fortnight fn equiv 2 wk = 1 209 600 s
helek equiv 11 080 h = 33 s
Hipparchic cycle equiv 4 Callippic cycles - 1 d = 9593 424 times 109 s
hour h equiv 60 min = 3 600 s
jiffy j equiv 160 s = 016 s
jiffy (alternate) ja equiv 1100 s = 10 ms
ke (quarter of an hour) equiv frac14 h = 196 d = 60 times 60 4 s = 900 s= 60 4 min = 15 min
Conversion of units 13
ke (traditional) equiv 1100 d = 24 times 60 times 60 100 s =864 s = 24 60 100min = 144 min
lustre lustrum equiv 5 a of 365 d = 15768 times 108 s
Metonic cycle enneadecaeteris equiv 110 mo (hollow) + 125 mo (full) = 6940 d asymp 19 a = 5996 16 times 108 s
millennium equiv 1 000 a (see below for definition of year length) = 1000 times year
milliday md equiv 11 000 d = 24 times 60 times 60 1 000 s= 864 s
minute min equiv 60 s due to leap seconds sometimes 59 s or 61 s = 60 s
moment equiv 90 s = 90 s
month (full) mo equiv 30 d[20] = 2 592 000 s
month (Greg av) mo Average Gregorian month = 365242512 d = 30436875 d asymp 26297 times 106 s
month (hollow) mo equiv 29 d[20] = 2 505 600 s
month (synodic) mo Cycle time of moon phases asymp 29530589 days (Average) asymp 2551 times 106 s
octaeteris = 48 mo (full) + 48 mo (hollow) + 3 mo (full)[21] [22] = 8 aof 36525 d = 2922 d
= 2524 608 times 108 s
Planck time equiv (Gℏc5)frac12 asymp 1351 211 868 times 10minus43
s
second s time of 9 192 631 770 periods of the radiation correspondingto the transition between the 2 hyperfine levels of the groundstate of the caesium 133 atom at 0 K[8] (but other secondsare sometimes used in astronomy)
(SI base unit)
shake equiv 10minus8 s = 10 ns
sigma equiv 10minus6 s = 1 μs
Sothic cycle equiv 1 461 a of 365 d = 4607 4096 times 1010 s
svedberg S equiv 10minus13 s = 100 fs
week wk equiv 7 d = 604 800 s
year (Gregorian) a y oryr
= 3652425 d average calculated from common years (365d) plus leap years (366 d) on most years divisible by 4 Seeleap year for details
= 31 556 952 s
year (Julian) a y oryr
= 36525 d average calculated from common years (365 d)plus one leap year (366 d) every four years
= 31 557 600 s
year (sidereal) a y oryr
equiv time taken for Sun to return to the same position withrespect to the stars of the celestial sphere
asymp 365256 363 d asymp 31558 1497632 s
year (tropical) a y oryr
equiv Length of time it takes for the Sun to return to the sameposition in the cycle of seasons
asymp 365242 190 d asymp 31556 925 s
Where UTC is observed the length of timeunits longer than 1 s may increase or decreaseby 1 s if a leap second occurs during the timeinterval of interest
Conversion of units 14
Frequency
Frequency
Name of unit Symbol Definition Relation to SI units
hertz (SI unit) Hz equiv Number of cycles per second = 1 Hz = 1s
revolutions per minute rpm equiv One unit rpm equals one rotation completed around a fixed axis in one minute of time asymp0104719755 rads
Speed or velocity
Speed
Name of unit Symbol Definition Relation to SI units
foot per hour fph equiv 1 fth asymp 8466 667 times 10minus5
ms
foot per minute fpm equiv 1 ftmin = 508 times 10minus3 ms
foot per second fps equiv 1 fts = 3048 times 10minus1 ms
furlong perfortnight
equiv furlongfortnight asymp 1663 095 times 10minus4
ms
inch per minute ipm equiv 1 inmin asymp 423 333 times 10minus4 ms
inch per second ips equiv 1 ins = 254 times 10minus2 ms
mach number M Ratio of the speed to the speed of sound in the medium Varies especially with temperatureAbout 761 mph (1225 kph) in air at sea level to about 660 mph (1062 kph) at jet altitudesUnitless
asymp 340 to 295 ms foraircraft
metre per second(SI unit)
ms equiv 1 ms = 1 ms
mile per hour mph equiv 1 mih = 0447 04 ms
mile per minute mpm equiv 1 mimin = 268224 ms
mile per second mps equiv 1 mis = 1 609344 ms
speed of light invacuum
c equiv 299 792 458 ms = 299 792 458 ms
speed of sound inair
s Varies especially with temperature About 761 mph (1225 kph) in air at sea level to about660 mph (1062 kph) at jet altitudes
asymp 340 to 295 ms ataircraft altitudes
A velocity consists of a speed combined with a direction the speed part of the velocity takes units of speed
Conversion of units 15
Flow (volume)
Flow
Name of unit Symbol Definition Relation to SI units
cubic foot per minute CFM equiv 1 ft3min = 4719474432 times 10minus4 m3s
cubic foot per second ft3s equiv 1 ft3s = 0028316846592 m3s
cubic inch per minute in3min equiv 1 in3min = 27311773 times 10minus7 m3s
cubic inch per second in3s equiv 1 in3s = 16387064 times 10minus5 m3s
cubic metre per second (SIunit)
m3s equiv 1 m3s = 1 m3s
gallon (US fluid) per day GPD equiv 1 gald = 4381263638 times 10minus8 m3s
gallon (US fluid) per hour GPH equiv 1 galh = 1051503273 times 10minus6 m3s
gallon (US fluid) per minute GPM equiv 1 galmin = 630901964 times 10minus5 m3s
litre per minute LPM equiv 1 Lmin = 16 times 10minus5 m3s
Acceleration
Acceleration
Name of unit Symbol Definition Relation to SI units
foot per hour per second fphs equiv 1 ft(hmiddots) asymp 8466 667 times 10minus5
ms2
foot per minute per second fpms equiv 1 ft(minmiddots) = 508 times 10minus3 ms2
foot per second squared fps2 equiv 1 fts2 = 3048 times 10minus1 ms2
gal galileo Gal equiv 1 cms2 = 10minus2 ms2
inch per minute per second ipms equiv 1 in(minmiddots) asymp 4233 333 times 10minus4
ms2
inch per second squared ips2 equiv 1 ins2 = 254 times 10minus2 ms2
knot per second kns equiv 1 kns asymp 5144 444 times 10minus1
ms2
metre per second squared (SI unit) ms2 equiv 1 ms2 = 1 ms2
mile per hour per second mphs equiv 1 mi(hmiddots) = 44704 times 10minus1 ms2
mile per minute per second mpms equiv 1 mi(minmiddots) = 268224 ms2
mile per second squared mps2 equiv 1 mis2 = 1609 344 times 103 ms2
standard gravity g equiv 9806 65 ms2 = 9806 65 ms2
Conversion of units 16
Force
Force
Name of unit Symbol Definition Relation to SI units
atomic unit of force equiv memiddotα2middotc2a0 asymp 8238 722 06 times 10minus8 N
[23]
dyne (cgs unit) dyn equiv gmiddotcms2 = 10minus5 N
kilogram-force kilopondgrave-force
kgf kp Gf equiv g times 1 kg = 9806 65 N
kip kip-force kip kipfklbf
equiv g times 1 000 lb = 4448 221 6152605 times 103 N
milligrave-force gravet-force mGf gf equiv g times 1 g = 9806 65 mN
newton (SI unit) N A force capable of giving a mass of one kg an acceleration of one metreper second per second[24]
= 1 N = 1 kgmiddotms2
ounce-force ozf equiv g times 1 oz = 0278 013 850 9537812 N
pound lb equiv slugmiddotfts2 = 4448 230 531 N
pound-force lbf equiv g times 1 lb = 4448 221 615 2605 N
poise (cgs unit) P equiv 10minus1 Pamiddots = 01 Pamiddots
pound per foot hour lb(ftmiddoth) equiv 1 lb(ftmiddoth) asymp 4133 789 times 10minus4 Pamiddots
pound per foot second lb(ftmiddots) equiv 1 lb(ftmiddots) asymp 1488164 Pamiddots
pound-force second per square foot lbfmiddotsft2 equiv 1 lbfmiddotsft2 asymp 4788026 Pamiddots
pound-force second per square inch lbfmiddotsin2 equiv 1 lbfmiddotsin2 asymp 6894757 Pamiddots
Conversion of units 21
Kinematic viscosity
Kinematic viscosity
Name of unit Symbol Definition Relation to SI units
square foot per second ft2s equiv 1 ft2s = 009290304 m2s
square metre per second (SI unit) m2s equiv 1 m2s = 1 m2s
stokes (cgs unit) St equiv10minus4 m2s
= 10minus4 m2s
Electric current
Electric current
Name of unit Symbol Definition Relation to SI units
ampere (SI base unit) A equiv The constant current needed to produce a force of 2 times 10minus7 newton per metre betweentwo straight parallel conductors of infinite length and negligible circular cross-sectionplaced one metre apart in a vacuum[8]
= 1 A
electromagnetic unitabampere (cgs unit)
abamp equiv 10 A = 10 A
esu per secondstatampere (cgs unit)
esus equiv (01 Amiddotms) c asymp3335641 times 10minus10 A
Electric charge
Electric charge
Name of unit Symbol Definition Relation to SI units
abcoulomb electromagnetic unit (cgsunit)
abC emu equiv 10 C = 10 C
atomic unit of charge au equiv e asymp 1602 176462 times 10minus19 C
coulomb (SI unit) C equiv The amount of electricity carried in one second of time by oneampere of current[24]
= 1 C = 1 Amiddots
faraday F equiv 1 mol times NAmiddote asymp 96 4853383 C
statcoulomb franklin electrostatic unit(cgs unit)
statC Fresu
equiv (01 Amiddotm) c asymp 3335 641 times 10minus10 C
Conversion of units 22
Electric dipole
Electric dipole
Name of unit Symbol Definition Relation to SI units
atomic unit of electric dipole moment ea0 asymp 8478 352 81 times 10minus30
Cmiddotm[28]
Electromotive force electric potential difference
Voltage electromotive force
Name ofunit
Symbol Definition Relation to SI units
abvolt (cgsunit)
abV equiv 1 times 10minus8 V = 1 times 10minus8 V
statvolt (cgsunit)
statV equiv cmiddot (1 μJAmiddotm) = 299792 458 V
volt (SIunit)
V The difference in electric potential across two points along a conducting wire carrying one ampereof constant current when the power dissipated between the points equals one watt[24]
= 1 V = 1 WA = 1kgmiddotm2(Amiddots3)
Electrical resistance
Electrical resistance
Name ofunit
Symbol Definition Relation to SI units
ohm (SIunit)
Ω The resistance between two points in a conductor when one volt of electric potential differenceapplied to these points produces one ampere of current in the conductor[24]
= 1 Ω = 1 VA = 1kgmiddotm2(A2middots3)
Capacitance
Capacitors ability to store charge
Name ofunit
Symbol Definition Relation to SI units
farad (SIunit)
F The capacitance between two parallel plates that results in one volt of potential difference whencharged by one coulomb of electricity[24]
= 1 F = 1 CV = 1A2middots4(kgmiddotm2)
Conversion of units 23
Magnetic flux
magnetic flux
Name of unit Symbol Definition Relation to SI units
maxwell (CGSunit)
Mx equiv 10minus8 Wb[29] = 1 times 10minus8 Wb
weber (SIunit)
Wb Magnetic flux which linking a circuit of one turn would produce in it an electromotive force of1 volt if it were reduced to zero at a uniform rate in 1 second[24]
= 1 Wb = 1 Vmiddots = 1kgmiddotm2(Amiddots2)
Magnetic flux density
What physicists call Magnetic field is called Magnetic flux density by electrical engineersand magnetic induction by applied mathematicians and electrical engineers
Name of unit Symbol Definition Relation to SI units
gauss (CGS unit) G equiv Mxcm2 = 10minus4
T= 1 times 10minus4 T [30]
tesla (SI unit) T equiv Wbm2 = 1 T = 1 Wbm2 = 1kg(Amiddots2)
Inductance
Inductance
Name ofunit
Symbol Definition Relation to SI units
henry (SIunit)
H The inductance of a closed circuit that produces one volt of electromotive force when the current inthe circuit varies at a uniform rate of one ampere per second[24]
= 1 H = 1 WbA = 1kgmiddotm2(Amiddots)2
Temperature
Temperature
Name of unit Symbol Definition Conversion to kelvin
degree Celsius degC degC equiv K minus 27315 [K] equiv [degC] + 27315
degree Delisle degDe [K] = 37315 minus [degDe] times 23
degree Fahrenheit degF degF equiv degC times 95 + 32 [K] equiv ([degF] + 45967) times 59
degree Newton degN [K] = [degN] times 10033 + 27315
degree Rankine degR degRa degR equiv K times 95 [K] equiv [degR] times 59
degree Reacuteaumur degReacute [K] = [degReacute] times 54 + 27315
degree Roslashmer degRoslash [K] = ([degRoslash] minus 75) times 4021 + 27315
kelvin (SI baseunit)
K equiv 127316 of the thermodynamic temperature of the triple point of water[8] equiv 1 K
Conversion of units 24
Information entropy
Information entropy
Name of unit Symbol Definition Relation to SI units Relation to bits
SI unit JK equiv JK = 1 JK
nat nip nepit nat equiv kB = 1380 650 5(23) times 10minus23 JK
bit shannon bit b Sh equiv ln(2) times kB = 9569 940 (16) times 10minus24 JK = 1 bit
ban hartley ban Hart equiv ln(10) times kB = 3179 065 3(53) times 10minus23 JK
nibble equiv 4 bits = 3827 976 0(64) times 10minus23 JK = 22 bit
byte B equiv 8 bits = 7655 952 (13) times 10minus23 JK = 23 bit
kilobyte (decimal) kB equiv 1 000 B = 7655 952 (13) times 10minus20 JK
kilobyte (kibibyte) KB KiB equiv 1 024 B = 7839 695 (13) times 10minus20 JK = 210 bit
Often information entropy is measured in shannons whereas the (discrete) storage space of digital devices ismeasured in bits Thus uncompressed redundant data occupy more than one bit of storage per shannon ofinformation entropy The multiples of a bit listed above are usually used with this meaning Other times the bit isused as a measure of information entropy and is thus a synonym of shannon
Luminous intensityThe candela is the preferred nomenclature for the SI unit
Luminous intensity
Name of unit Symbol Definition Relation toSI units
candela (SI baseunit) candle
cd The luminous intensity in a given direction of a source that emits monochromatic radiation offrequency 540 times 1012 hertz and that has a radiant intensity in that direction of 1683 watt persteradian[8]
= 1 cd
candlepower (new) cp equiv cd The use of candlepower as a unit is discouraged due to its ambiguity = 1 cd
candlepower (oldpre-1948)
cp Varies and is poorly reproducible[31] Approximately 0981 cd[14] asymp 0981 cd
Luminance
Conversion of units 25
Luminance
Name of unit Symbol Definition Relation to SI units
candela per square foot cdft2 equiv cdft2 asymp10763910417 cdm2
candela per square inch cdin2 equiv cdin2 asymp 15500031 cdm2
candela per square metre (SI unit) nit (deprecated[14] ) cdm2 equiv cdm2 = 1 cdm2
Name of unit Symbol Definition Relation to SI units
lumen (SIunit)
lm equiv cdmiddotsr = 1 lm = 1 cdmiddotsr
Illuminance
Illuminance
Name of unit Symbol Definition Relation to SI units
footcandle lumen per square foot fc equiv lmft2 = 10763910417 lx
lumen per square inch lmin2 equiv lmin2 asymp 15500031 lx
lux (SI unit) lx equiv lmm2 = 1 lx = 1 lmm2
phot (CGS unit) ph equiv lmcm2 = 1 times 104 lx
Radiation - source activity
Conversion of units 26
Radioactivity
Name of unit Symbol Definition Relation to SI units
becquerel (SIunit)
Bq equiv Number of disintegrations per second = 1 Bq = 1s
curie Ci equiv 37 times 1010 Bq = 37 times 1010 Bq [32]
rutherford (H) rd equiv 1 MBq = 1 times 106 Bq
Please note that although becquerel (Bq) and hertz (Hz) both ultimately refer to the same SI base unit (sminus1) Hz isused only for periodic phenomena and Bq is only used for stochastic processes associated with radioactivity[33]
Radiation - exposure
Radiation - exposure
Name of unit Symbol Definition Relation to SI units
roentgen R 1 R equiv 258 times 10minus4 Ckg[29] = 258 times 10minus4 Ckg
The roentgen is not a SI unit and the NIST strongly discourages its continued use[34]
Radiation - absorbed dose
Radiation - absorbed dose
Name of unit Symbol Definition Relation to SI units
Name of unit Symbol Definition Relation to SI units
Roumlntgen equivalent man rem equiv 001 Sv = 001 Sv
sievert (SI unit) Sv equiv 1 Jkg[33] = 1 Sv
Although the definitions for sievert (Sv) and gray (Gy) would seem to indicate that they measure the same quantitiesthis is not the case The effect of receiving a certain dose of radiation (given as Gy) is variable and depends on manyfactors thus a new unit was needed to denote the biological effectiveness of that dose on the body this is known asthe equivalent dose and is shown in Sv The general relationship between absorbed dose and equivalent dose can berepresented as
H = Q middot D
where H is the equivalent dose D is the absorbed dose and Q is a dimensionless quality factor Thus for anyquantity of D measured in Gy the numerical value for H measured in Sv may be different[36]
Conversion of units 27
Software toolsHome and office computers come with converters in bundled spreadsheet applications or can access free convertersvia the Internet Units and measurements can be easily converted using these tools but only if the units are explicitlydefined and the conversion is compatible (eg cmHg to kPa)
Free conversion softwarebull Units (software) a popular cross-platform command-line utilitybull Converter [37] contextual unit converter for Mozilla Firefox browsersbull Converber [38] portable application converting utilitybull calculla [39] calculla - online web convertersbull iMetrix [40] - unit converter for xpbull uniteasy [41] online scientific unit conversionbull Unit Converter Add-in for Excel [42] - allow a large selection of unit conversions within the Microsoft Excel
spread sheet programbull Unit Converter [43] simple and extensible unit converterbull Portable Unit Converter [44] including 4500 units 33 unit-categories and the possibility to create custom units
General commercial sources of convertersbull Advanced electronic calculators have unit-conversion functionalitybull Spreadsheet programs usually provide conversion functions or formulas or the user can write their ownbull Commercial mathematical scientific and technical applications often include converters
See also
bull Accuracy and precisionbull English unitsbull False precisionbull Imperial unitsbull International System of Unitsbull Mesures usuellesbull Metric system
bull Natural unitsbull Roundingbull Significant figuresbull Temperature conversionbull United States customary unitsbull Units conversion by factor-labelbull Units of measurement
External linksbull British law Units of measurement regulations 1995 [45]
bull ConvertBuster [46] Variety of conversion tools to convert easilybull How Many A dictionary of units of measurement [47]
bull NIST Fundamental physical constants mdash Non-SI units [48]PDF (357 KB)bull NIST Guide to SI Units [49] Many conversion factors listedbull Online Conversion Calculators [50] Very extensive list of conversions from-to equvalent unitsbull The Unified Code for Units of Measure [51]
bull Units Symbols and Conversions XML Dictionary [52]
bull Multilingual Online Conversion of Units [53]
bull Temperature Converter [54]
Conversion of units 28
References[1] United States Naval Observatory (2009) Selected Astronomical Constants 2009 (http asa usno navy mil SecK 2009
Astronomical_Constants_2009 txt) Accessed May 10 2009[2] NIST Reference on Constants Units and Uncertainty (http physics nist gov cgi-bin cuu Valuebohrrada0|search_for=Bohr+
radius)(2006) National Institute of Standards and Technology Retrieved February 22 2008[3] National Institute of Standards and Technology General Tables of Units of Measurement (http ts nist gov WeightsAndMeasures
Publications appxc cfm)[4] Lide D (Ed) (1990) Handbook of Chemistry and Physics (71st ed) Boca Raton FL CRC Press Section 1[5] National Bureau of Standards (June 30 1959) Refinement of values for the yard and the pound Federal Register viewed September 20
2006 at National Geodetic Survey web site (http www ngs noaa gov PUBS_LIB FedRegister FRdoc59-5442 pdf)[6] The International Astronomical Union and Astronomical Units (http www iau org public_press themes measuring )[7] Klein Herbert Arthur (1988) The Science of Measurement a Historical Survey Mineola NY Dover Publications 0-4862-5839-4[8] The International System of Units Section 21 (http www bipm org en si si_brochure chapter2 2-1 ) (8 ed) Bureau International des
Poids et Mesures 2006 retrieved August 26 2009[9] International System of Units (http www bipm org en si si_brochure chapter4 table8 html) 8th ed (2006) Bureau International des
Poids et Mesures Section 41 Table 8[10] P Kenneth Seidelmann Ed (1992) Explanatory Supplement to the Astronomical Almanac Sausalito CA University Science Books p 716
and sv parsec in Glossary[11] Whitelaw Ian (2007) A Measure of All Things The Story of Man and Measurement (http books google com
booksid=3zgGEWM5-iAC) New York Macmillan 0-312-37026-1 p 152[12] De Vinne Theodore Low (1900) The practice of typography a treatise on the processes of type-making the point system the names sizes
styles and prices of plain printing types (http books google com booksid=R4-DjphIpLMC) 2nd ed New York The Century Co p142ndash150
[13] Pasko Wesley Washington (1894) American dictionary of printing and bookmaking (http books google combooksid=Z_QUAAAAIAAJ) (1894) New York Howard Lockwood p 521
[14] Rowlett Russ (2005) How Many A Dictionary of Units of Measurement (http www unc edu ~rowlett units index html)[15] Thompson A and Taylor BN (2008) Guide for the Use of the International System of Units (SI) National Institute of Standards and
Technology Special Publication 811 p 57[16] US Code of Federal Regulations Title 21 Section 1019 Paragraph (b)(5)(viii) (http ecfr gpoaccess gov cgi t text text-idxc=ecframp
rgn=div8amp view=textamp node=212 0 1 1 2 1 1 6amp idno=21) retrieved August 29 2009[17] Barry N Taylor Ed NIST Special Publication 330 The International System of Units (SI) (http physics nist gov Pubs SP330 sp330
pdf) (2001 Edition) Washington US Government Printing Office 43The 12th Conference Generale des Poids et Mesures(CGPM)hellipdeclares that the word ldquolitrerdquo may be employed as a special name for the cubic decimetre
[18] CODATA Value atomic uint of mass (http physics nist gov cgi-bin cuu Valuettme|search_for=atomic+ unit+ of+ mass) (2006)National Institute of Standards and Technology Retrieved 16 September 2008
[19] The Swiss Federal Office for Metrology gives Zentner on a German language web page (http www metas ch de scales systemch html)and quintal on the English translation of that page (http www metas ch en scales systemch html) the unit is marked speacutecifiquementsuisse
[20] Pedersen O (1983) Glossary in Coyne G Hoskin M and Pedersen O Gregorian Reform of the Calendar Proceedings of the VaticanConference to Commemorate its 400th Anniversary Vatican Observatory Available from Astrophysics Data System
[21] Richards EG (1998) Mapping Time Oxford University Press pp 94ndash95 ISBN 0-19-850413-6[22] Steel Duncan (2000) Marking Time John Wiley amp Sons p 46 ISBN 0-471-29827-1[23] CODATA Value atomic unit of force (http physics nist gov cuu Constants ) (2006) National Institute of Standards and Technology
Retrieved September 14 2008[24] [[Comiteacute International des Poids et Mesures (http www bipm org en CIPM db 1946 2 )] Resolution 2] 1946 retrieved August 26
2009[25] Barry N Taylor (April 1995) Guide for the Use of the International System of Units (SI) (http physics nist gov cuu pdf sp811 pdf)
(NIST Special Publication 811) Washington DC US Government Printing Office pp 57ndash68[26] Barry N Taylor (April 1995) Guide for the Use of the International System of Units (SI) (NIST Special Publication 811) Washington DC
US Government Printing Office p 5[27] International System of Units (http www bipm org en si si_brochure chapter4 table7 html) 8th ed (2006) Bureau International des
Poids et Mesures Section 41 Table 7[28] The NIST Reference on Constants Units and Uncertainty (http physics nist gov cgi-bin cuu Valueauedm) 2006 retrieved August
26 2009[29] NIST Guide to SI Units Appendix B9 (http physics nist gov Pubs SP811 appenB9 html) retrieved August 27 2009[30] Standard for the Use of the International System of Units (SI) The Modern Metric System IEEEASTM SI 10-1997 (1997) New York and
West Conshohocken PA Institute of Electrical and Electronics Engineers and American Society for Testing and Materials Tables A1through A5
Conversion of units 29
[31] The NIST Reference on Constants Units and Uncertainty (http physics nist gov cuu Units candela html) retrieved August 28 2009[32] Ambler Thompson amp Barry N Taylor (2008) Guide for the Use of the International System of Units (SI) (http physics nist gov cuu
pdf sp811 pdf) Special Publication 811 Gaithersburg MD National Institute of Standards and Technology p 10[33] The International System of Units Section 222 Table 3 (http www bipm org en si si_brochure chapter2 2-2 table3 html) (8 ed)
Bureau International des Poids et Mesures 2006 retrieved August 27 2009[34] The NIST Guide to the SI (Special Publication 811) section 52 (http physics nist gov Pubs SP811 sec05 html5 2) 2008 retrieved
August 27 2009[35] Ambler Thompson amp Barry N Taylor (2008) Guide for the Use of the International System of Units (SI) (http physics nist gov cuu
pdf sp811 pdf) Special Publication 811 Gaithersburg MD National Institute of Standards and Technology p 5[36] [[Comiteacute international des poids et mesures (http www bipm org en CIPM db 2002 2 )] 2002 Recommendation 2] retrieved
August 27 2009[37] http converter mozdev org[38] http www xyntec com converber htm[39] http www calculla com[40] http illusions hu index phptask=100amp lang=0amp statpage=86[41] http www uniteasy com[42] http www tenderwire com wikipedialandingpage[43] http www kamlex com index phpoption=com_contentamp view=articleamp id=53amp Itemid=55[44] http www sttmedia com unitconverter[45] http www hmso gov uk si si1995 Uksi_19951804_en_2 htm[46] http www convertbuster com[47] http www unc edu ~rowlett units[48] http physics nist gov cuu Document nonsi_in_1998 pdf[49] http physics nist gov Pubs SP811 appenB9 html[50] http www onlineconversion com[51] http aurora rg iupui edu ~schadow units UCUM ucum html[52] http www posc org refs poscUnits20 xml[53] http www imperialtometric com[54] http www tampile com
Article Sources and Contributors 30
Article Sources and ContributorsConversion of units Source httpenwikipediaorgwindexphpoldid=373975089 Contributors 1571781xxx 7 A-giau AVSI Acather96 Ahoerstemeier Alexius08 Altenmann AndreEngels Andrewa Andy120290 Anonymi Ariconte Army1987 ArnoldReinhold Arthur3030 Aspects AxelBoldt AzaToth Azikala BW95 Bdesham Beland Bensaccount Bkumartvm Blackand White BlaiseFEgan BlueEarth Bobblewik Borbrav Bpmullins Bryan Derksen C J B Scholten CORNELIUSSEON CTZMSC3 Calltech Camerajohn Chaosfeary Charles MatthewsChris the speller Cmdrjameson Colonies Chris Conversion script Cope555 Crappy13 Crissov CyrilB DARTH SIDIOUS 2 DMacks DanielCD Dark Formal DarkestSideX DekisugiDenelson83 Dhp1080 Dicklyon DirkvdM Donald Duck Donarreiskoffer Dramatic Dyss DAringsbquougosz Egil Ehrenkater Ejohnsonboulder Elexmax Elf Emokhberi Enon Eob Epbr123Euchiasmus Fathead99 Father Goose Fella22 Femto FernandoAC Fibula Flutefreek Fred Bauder Fredrik Fuhghettaboutit Fuzheado Gaff Gene Nygaard Georgiy1996 Gerry AshtonGiftlite Gilliam Glenn L GoingBatty Goobergunch Gregsexton Greyengine5 Grunt Gurch Gutza HLHJ Haemo Hammersbach Heracles31 Herbee Heron HikerBush Hqb IcairnsIgiffin Indefatigable Isis JBobbitt JHunterJ Jabowery JakeVortex Jamicanmonkey Jason Begin Jay Jc3s5h Jcronen1 Jdoherty Jeffz1 Jeronimo Jimmuhk Jimp Jimwilliams57 JoeinwapJohndburger Josh Parris Jq4bagiq Kaihsu KaneWang Keenan Pepper Kevin Rector KeyStorm Khukri Kurtan Lee Daniel Crocker LightYear Linuxoidoz Liv4christ210 Loggie Lolo252Lupinelawyer M ichaeligl MJCdetroit MTC Mac MacMcF Magore Markus Kuhn Masterqwe MaxHund Maxamegalon2000 Mbeychok Meggar Mh26 Michael Daly Michael Hardy MichelAudy Mikelifeguard Mikhailov Kusserow Mindbuilder Missvain Monger Mr bulow MrOllie MrZhuKeeper Muro de Aguas Mwanner Mwtoews Nandesuka Natkeeran Ndsg NgjaimeNhy67ygv Nick Y Nick123 NickPenguin Ninjagecko Noe Nosilleg Now3r3 Obelix homologator Oldadamml Oleg Alexandrov Olivier Ortolan88 OwenBlacker Pac72 PassargeaPatrick Paul Martin Peter Horn Physchim62 Piels Pierdm Pmanderson Prometheus235 Quadell QuantumEleven Quod erat demonstrandum 314159 Radagast83 Rccoms RedWolfReinyday Revipm Rexparry sydney Reyk Rhetth Rhialto Rich Farmbrough Richard Myers Rjwilmsi Rlsheehan Robin Barry RoySmith Rpwolfgram SD6-Agent SGBailey SamuelLowry Samw Sander123 Seabhcan SebastianHelm Sherbert1 Shinhan Shrew Sietse Snel SimonP Sinbaddasail0r Skotte Smalljim SomeHuman Spencer Srleffler StarwarsmastergeekSteacoon StefanK SteveRamone Stevertigo Stokerm Suisui Sunev Superboy112233 Superm401 Synchronism Tacoman1996 Tarquin Taw Teratornis The Man in Question ThierrycThingg Thinking of England Thunderbird2 Timwi Tobias Hoevekamp Tomasr Tonsofpcs Toon05 Topsykretts2512 Trekphiler Tuwile Twanvl Uday147502 Unitman00 UrhixidurUtherSRG Vargenau Vsmith WarrenPlatts Wasell Welsh Whispering Wikinger Wolfkeeper Wtmitchell XJamRastafire Xenonice Yath Zginder Zibem Zocky Zotel 713 anonymousedits
Name of unit Symbol Definition Relation to SIunits
angular mil micro equiv 2π6400 rad asymp 0981 748 times 10minus3
rad
arcminute equiv 1deg60 asymp 0290 888 times 10minus3
rad
arcsecond equiv 1deg3600 asymp 4848 137 times 10minus6
rad
centesimal minuteof arc
equiv 1 grad100 asymp 0157 080 times 10minus3
rad
centesimal secondof arc
equiv 1 grad(10 000) asymp 1570 796 times 10minus6
rad
degree (of arc) deg equiv 1360 of a revolution equiv π180 rad asymp 17453293 times 10minus3 rad
grad gradian gon grad equiv 1400 of a revolution equiv 2π400 rad equiv 09deg asymp 15707963 times 10minus3 rad
octant equiv 45deg asymp 0785 398 rad
quadrant equiv 90deg asymp 1570 796 rad
radian (SI unit) rad The angle subtended at the center of a circle by an arc whose length is equal to the circlesradius One full revolution encompasses 2π radians
= 1 rad
sextant equiv 60deg asymp 1047 198 rad
sign equiv 30deg asymp 0523 599 rad
Conversion of units 10
Solid angle
Solid angle
Name of unit Symbol Definition Relation to SIunits
steradian (SIunit)
sr The solid angle subtended at the center of a sphere of radius r by a portion of the surface of the spherehaving an area r2 A sphere encompasses 4π sr[14]
= 1 sr
MassNotesbull See Weight for detail of massweight distinction and conversionbull In this table the unit gee is used to denote standard gravity in order to avoid confusion with the g symbol for
gramsbull In physics the pound of mass is sometimes written lbm to distinguish it from the pound-force (lbf) It should not
be read as the mongrel unit pound metre
Mass
Name of unit Symbol Definition Relation to SI units
atomic mass unit unified u AMU asymp 1660 538 73 times 10minus27 plusmn 13 times 10minus36 kg
atomic unit of mass electron restmass
me asymp 9109 382 15 times 10minus31 plusmn 45 times 10minus39 kg[18]
bag (coffee) equiv 60 kg = 60 kg
bag (Portland cement) equiv 94 lb av = 42637 682 78 kg
barge equiv 22frac12 sh tn = 20 411656 65 kg
carat kt equiv 3 16 gr asymp 205196 548 333 mg
carat (metric) ct equiv 200 mg = 200 mg
clove equiv 8 lb av = 3628 738 96 kg
crith asymp 899349 mg
dalton Da asymp 1660 902 10 times 10minus27 plusmn 13 times 10minus36 kg
dram (apothecary troy) dr t equiv 60 gr = 3887 9346 g
dram (avoirdupois) dr av equiv 27 1132 gr = 1771 845 195 3125 g
electronvolt eV equiv 1 eV (energy unit) c2 = 17826 times 10minus36 kg
gamma γ equiv 1 μg = 1 μg
grain gr equiv 17000 lb av equiv 64798 91 mg
grave G grave was the original name of the kilogram equiv 1 kg
hundredweight (long) long cwt orcwt
equiv 112 lb av = 50802 345 44 kg
hundredweight (short) cental sh cwt equiv 100 lb av = 45359 237 kg
hyl (CGS unit) equiv 1 gee times 1 g times 1 s2m = 9806 65 g
hyl (MKS unit) equiv 1 gee times 1 kg times 1 s2m = 9806 65 kg
Conversion of units 11
kilogram kg equiv mass of the prototype near Paris (asymp mass of 1L ofwater)
equiv 1 kg (SI base unit)[8]
kip kip equiv 1000 lb av = 453592 37 kg
mark equiv 8 oz t = 248827 8144 g
mite equiv 120 gr = 3239 9455 mg
mite (metric) equiv 120 g = 50 mg
ounce (apothecary troy) oz t equiv 112 lb t = 31103 4768 g
ounce (avoirdupois) oz av equiv 116 lb = 28349 523 125 g
ounce (US food nutritionlabeling)
oz equiv 28 g[16] = 28 g
pennyweight dwt pwt equiv 120 oz t = 1555 173 84 g
point equiv 1100 ct = 2 mg
pound (avoirdupois) lb av equiv 0453 592 37 kg = 7000 grains equiv 0453 592 37 kg
pound (metric) equiv 500 g = 500 g
pound (troy) lb t equiv 5 760 grains = 0373 241 7216 kg
quarter (Imperial) equiv 14 long cwt = 2 st = 28 lb av = 12700 586 36 kg
quarter (informal) equiv frac14 short tn = 226796 185 kg
quarter long (informal) equiv frac14 long tn = 254011 7272 kg
quintal (metric) q equiv 100 kg = 100 kg
scruple (apothecary) s ap equiv 20 gr = 1295 9782 g
sheet equiv 1700 lb av = 6479891 mg
slug geepound slug equiv 1 gee times 1 lb av times 1 s2ft asymp 14593 903 kg
stone st equiv 14 lb av = 6350 293 18 kg
ton assay (long) AT equiv 1 mg times 1 long tn divide 1 oz t asymp 32666 667 g
ton assay (short) AT equiv 1 mg times 1 sh tn divide 1 oz t asymp 29166 667 g
ton long long tn or ton equiv 2 240 lb = 1 016046 9088 kg
ton short sh tn equiv 2 000 lb = 907184 74 kg
tonne (mts unit) t equiv 1 000 kg = 1 000 kg
wey equiv 252 lb = 18 st = 114305 277 24 kg (variants exist)
Zentner Ztr Definitions vary see [19] and[14]
Density
Conversion of units 12
Density
Name of unit Symbol Definition Relation to SI units
gram per millilitre gmL equiv gmL = 1000 kgm3
kilogram per cubic metre (SI unit) kgm3 equiv kgm3 = 1 kgm3
slug per cubic foot slugft3 equiv slugft3 asymp 5153788184 kgm3
Time
Time t
Name of unit Symbol Definition Relation to SI units
atomic unit of time au equiv a0(αmiddotc) asymp 2418 884 254 times 10minus17
s
Callippic cycle equiv 441 mo (hollow) + 499 mo (full) = 76 a of 36525 d = 2398 3776 times 109 s
century c equiv 100 a (see below for definition of year length) = 100 times year
day d = 24 h = 86400 s
day (sidereal) d equiv Time needed for the Earth to rotate once around its axisdetermined from successive transits of a very distantastronomical object across an observers meridian(International Celestial Reference Frame)
asymp 86 1641 s
decade dec equiv 10 a (see below for definition of year length) = 10 times year
fortnight fn equiv 2 wk = 1 209 600 s
helek equiv 11 080 h = 33 s
Hipparchic cycle equiv 4 Callippic cycles - 1 d = 9593 424 times 109 s
hour h equiv 60 min = 3 600 s
jiffy j equiv 160 s = 016 s
jiffy (alternate) ja equiv 1100 s = 10 ms
ke (quarter of an hour) equiv frac14 h = 196 d = 60 times 60 4 s = 900 s= 60 4 min = 15 min
Conversion of units 13
ke (traditional) equiv 1100 d = 24 times 60 times 60 100 s =864 s = 24 60 100min = 144 min
lustre lustrum equiv 5 a of 365 d = 15768 times 108 s
Metonic cycle enneadecaeteris equiv 110 mo (hollow) + 125 mo (full) = 6940 d asymp 19 a = 5996 16 times 108 s
millennium equiv 1 000 a (see below for definition of year length) = 1000 times year
milliday md equiv 11 000 d = 24 times 60 times 60 1 000 s= 864 s
minute min equiv 60 s due to leap seconds sometimes 59 s or 61 s = 60 s
moment equiv 90 s = 90 s
month (full) mo equiv 30 d[20] = 2 592 000 s
month (Greg av) mo Average Gregorian month = 365242512 d = 30436875 d asymp 26297 times 106 s
month (hollow) mo equiv 29 d[20] = 2 505 600 s
month (synodic) mo Cycle time of moon phases asymp 29530589 days (Average) asymp 2551 times 106 s
octaeteris = 48 mo (full) + 48 mo (hollow) + 3 mo (full)[21] [22] = 8 aof 36525 d = 2922 d
= 2524 608 times 108 s
Planck time equiv (Gℏc5)frac12 asymp 1351 211 868 times 10minus43
s
second s time of 9 192 631 770 periods of the radiation correspondingto the transition between the 2 hyperfine levels of the groundstate of the caesium 133 atom at 0 K[8] (but other secondsare sometimes used in astronomy)
(SI base unit)
shake equiv 10minus8 s = 10 ns
sigma equiv 10minus6 s = 1 μs
Sothic cycle equiv 1 461 a of 365 d = 4607 4096 times 1010 s
svedberg S equiv 10minus13 s = 100 fs
week wk equiv 7 d = 604 800 s
year (Gregorian) a y oryr
= 3652425 d average calculated from common years (365d) plus leap years (366 d) on most years divisible by 4 Seeleap year for details
= 31 556 952 s
year (Julian) a y oryr
= 36525 d average calculated from common years (365 d)plus one leap year (366 d) every four years
= 31 557 600 s
year (sidereal) a y oryr
equiv time taken for Sun to return to the same position withrespect to the stars of the celestial sphere
asymp 365256 363 d asymp 31558 1497632 s
year (tropical) a y oryr
equiv Length of time it takes for the Sun to return to the sameposition in the cycle of seasons
asymp 365242 190 d asymp 31556 925 s
Where UTC is observed the length of timeunits longer than 1 s may increase or decreaseby 1 s if a leap second occurs during the timeinterval of interest
Conversion of units 14
Frequency
Frequency
Name of unit Symbol Definition Relation to SI units
hertz (SI unit) Hz equiv Number of cycles per second = 1 Hz = 1s
revolutions per minute rpm equiv One unit rpm equals one rotation completed around a fixed axis in one minute of time asymp0104719755 rads
Speed or velocity
Speed
Name of unit Symbol Definition Relation to SI units
foot per hour fph equiv 1 fth asymp 8466 667 times 10minus5
ms
foot per minute fpm equiv 1 ftmin = 508 times 10minus3 ms
foot per second fps equiv 1 fts = 3048 times 10minus1 ms
furlong perfortnight
equiv furlongfortnight asymp 1663 095 times 10minus4
ms
inch per minute ipm equiv 1 inmin asymp 423 333 times 10minus4 ms
inch per second ips equiv 1 ins = 254 times 10minus2 ms
mach number M Ratio of the speed to the speed of sound in the medium Varies especially with temperatureAbout 761 mph (1225 kph) in air at sea level to about 660 mph (1062 kph) at jet altitudesUnitless
asymp 340 to 295 ms foraircraft
metre per second(SI unit)
ms equiv 1 ms = 1 ms
mile per hour mph equiv 1 mih = 0447 04 ms
mile per minute mpm equiv 1 mimin = 268224 ms
mile per second mps equiv 1 mis = 1 609344 ms
speed of light invacuum
c equiv 299 792 458 ms = 299 792 458 ms
speed of sound inair
s Varies especially with temperature About 761 mph (1225 kph) in air at sea level to about660 mph (1062 kph) at jet altitudes
asymp 340 to 295 ms ataircraft altitudes
A velocity consists of a speed combined with a direction the speed part of the velocity takes units of speed
Conversion of units 15
Flow (volume)
Flow
Name of unit Symbol Definition Relation to SI units
cubic foot per minute CFM equiv 1 ft3min = 4719474432 times 10minus4 m3s
cubic foot per second ft3s equiv 1 ft3s = 0028316846592 m3s
cubic inch per minute in3min equiv 1 in3min = 27311773 times 10minus7 m3s
cubic inch per second in3s equiv 1 in3s = 16387064 times 10minus5 m3s
cubic metre per second (SIunit)
m3s equiv 1 m3s = 1 m3s
gallon (US fluid) per day GPD equiv 1 gald = 4381263638 times 10minus8 m3s
gallon (US fluid) per hour GPH equiv 1 galh = 1051503273 times 10minus6 m3s
gallon (US fluid) per minute GPM equiv 1 galmin = 630901964 times 10minus5 m3s
litre per minute LPM equiv 1 Lmin = 16 times 10minus5 m3s
Acceleration
Acceleration
Name of unit Symbol Definition Relation to SI units
foot per hour per second fphs equiv 1 ft(hmiddots) asymp 8466 667 times 10minus5
ms2
foot per minute per second fpms equiv 1 ft(minmiddots) = 508 times 10minus3 ms2
foot per second squared fps2 equiv 1 fts2 = 3048 times 10minus1 ms2
gal galileo Gal equiv 1 cms2 = 10minus2 ms2
inch per minute per second ipms equiv 1 in(minmiddots) asymp 4233 333 times 10minus4
ms2
inch per second squared ips2 equiv 1 ins2 = 254 times 10minus2 ms2
knot per second kns equiv 1 kns asymp 5144 444 times 10minus1
ms2
metre per second squared (SI unit) ms2 equiv 1 ms2 = 1 ms2
mile per hour per second mphs equiv 1 mi(hmiddots) = 44704 times 10minus1 ms2
mile per minute per second mpms equiv 1 mi(minmiddots) = 268224 ms2
mile per second squared mps2 equiv 1 mis2 = 1609 344 times 103 ms2
standard gravity g equiv 9806 65 ms2 = 9806 65 ms2
Conversion of units 16
Force
Force
Name of unit Symbol Definition Relation to SI units
atomic unit of force equiv memiddotα2middotc2a0 asymp 8238 722 06 times 10minus8 N
[23]
dyne (cgs unit) dyn equiv gmiddotcms2 = 10minus5 N
kilogram-force kilopondgrave-force
kgf kp Gf equiv g times 1 kg = 9806 65 N
kip kip-force kip kipfklbf
equiv g times 1 000 lb = 4448 221 6152605 times 103 N
milligrave-force gravet-force mGf gf equiv g times 1 g = 9806 65 mN
newton (SI unit) N A force capable of giving a mass of one kg an acceleration of one metreper second per second[24]
= 1 N = 1 kgmiddotms2
ounce-force ozf equiv g times 1 oz = 0278 013 850 9537812 N
pound lb equiv slugmiddotfts2 = 4448 230 531 N
pound-force lbf equiv g times 1 lb = 4448 221 615 2605 N
poise (cgs unit) P equiv 10minus1 Pamiddots = 01 Pamiddots
pound per foot hour lb(ftmiddoth) equiv 1 lb(ftmiddoth) asymp 4133 789 times 10minus4 Pamiddots
pound per foot second lb(ftmiddots) equiv 1 lb(ftmiddots) asymp 1488164 Pamiddots
pound-force second per square foot lbfmiddotsft2 equiv 1 lbfmiddotsft2 asymp 4788026 Pamiddots
pound-force second per square inch lbfmiddotsin2 equiv 1 lbfmiddotsin2 asymp 6894757 Pamiddots
Conversion of units 21
Kinematic viscosity
Kinematic viscosity
Name of unit Symbol Definition Relation to SI units
square foot per second ft2s equiv 1 ft2s = 009290304 m2s
square metre per second (SI unit) m2s equiv 1 m2s = 1 m2s
stokes (cgs unit) St equiv10minus4 m2s
= 10minus4 m2s
Electric current
Electric current
Name of unit Symbol Definition Relation to SI units
ampere (SI base unit) A equiv The constant current needed to produce a force of 2 times 10minus7 newton per metre betweentwo straight parallel conductors of infinite length and negligible circular cross-sectionplaced one metre apart in a vacuum[8]
= 1 A
electromagnetic unitabampere (cgs unit)
abamp equiv 10 A = 10 A
esu per secondstatampere (cgs unit)
esus equiv (01 Amiddotms) c asymp3335641 times 10minus10 A
Electric charge
Electric charge
Name of unit Symbol Definition Relation to SI units
abcoulomb electromagnetic unit (cgsunit)
abC emu equiv 10 C = 10 C
atomic unit of charge au equiv e asymp 1602 176462 times 10minus19 C
coulomb (SI unit) C equiv The amount of electricity carried in one second of time by oneampere of current[24]
= 1 C = 1 Amiddots
faraday F equiv 1 mol times NAmiddote asymp 96 4853383 C
statcoulomb franklin electrostatic unit(cgs unit)
statC Fresu
equiv (01 Amiddotm) c asymp 3335 641 times 10minus10 C
Conversion of units 22
Electric dipole
Electric dipole
Name of unit Symbol Definition Relation to SI units
atomic unit of electric dipole moment ea0 asymp 8478 352 81 times 10minus30
Cmiddotm[28]
Electromotive force electric potential difference
Voltage electromotive force
Name ofunit
Symbol Definition Relation to SI units
abvolt (cgsunit)
abV equiv 1 times 10minus8 V = 1 times 10minus8 V
statvolt (cgsunit)
statV equiv cmiddot (1 μJAmiddotm) = 299792 458 V
volt (SIunit)
V The difference in electric potential across two points along a conducting wire carrying one ampereof constant current when the power dissipated between the points equals one watt[24]
= 1 V = 1 WA = 1kgmiddotm2(Amiddots3)
Electrical resistance
Electrical resistance
Name ofunit
Symbol Definition Relation to SI units
ohm (SIunit)
Ω The resistance between two points in a conductor when one volt of electric potential differenceapplied to these points produces one ampere of current in the conductor[24]
= 1 Ω = 1 VA = 1kgmiddotm2(A2middots3)
Capacitance
Capacitors ability to store charge
Name ofunit
Symbol Definition Relation to SI units
farad (SIunit)
F The capacitance between two parallel plates that results in one volt of potential difference whencharged by one coulomb of electricity[24]
= 1 F = 1 CV = 1A2middots4(kgmiddotm2)
Conversion of units 23
Magnetic flux
magnetic flux
Name of unit Symbol Definition Relation to SI units
maxwell (CGSunit)
Mx equiv 10minus8 Wb[29] = 1 times 10minus8 Wb
weber (SIunit)
Wb Magnetic flux which linking a circuit of one turn would produce in it an electromotive force of1 volt if it were reduced to zero at a uniform rate in 1 second[24]
= 1 Wb = 1 Vmiddots = 1kgmiddotm2(Amiddots2)
Magnetic flux density
What physicists call Magnetic field is called Magnetic flux density by electrical engineersand magnetic induction by applied mathematicians and electrical engineers
Name of unit Symbol Definition Relation to SI units
gauss (CGS unit) G equiv Mxcm2 = 10minus4
T= 1 times 10minus4 T [30]
tesla (SI unit) T equiv Wbm2 = 1 T = 1 Wbm2 = 1kg(Amiddots2)
Inductance
Inductance
Name ofunit
Symbol Definition Relation to SI units
henry (SIunit)
H The inductance of a closed circuit that produces one volt of electromotive force when the current inthe circuit varies at a uniform rate of one ampere per second[24]
= 1 H = 1 WbA = 1kgmiddotm2(Amiddots)2
Temperature
Temperature
Name of unit Symbol Definition Conversion to kelvin
degree Celsius degC degC equiv K minus 27315 [K] equiv [degC] + 27315
degree Delisle degDe [K] = 37315 minus [degDe] times 23
degree Fahrenheit degF degF equiv degC times 95 + 32 [K] equiv ([degF] + 45967) times 59
degree Newton degN [K] = [degN] times 10033 + 27315
degree Rankine degR degRa degR equiv K times 95 [K] equiv [degR] times 59
degree Reacuteaumur degReacute [K] = [degReacute] times 54 + 27315
degree Roslashmer degRoslash [K] = ([degRoslash] minus 75) times 4021 + 27315
kelvin (SI baseunit)
K equiv 127316 of the thermodynamic temperature of the triple point of water[8] equiv 1 K
Conversion of units 24
Information entropy
Information entropy
Name of unit Symbol Definition Relation to SI units Relation to bits
SI unit JK equiv JK = 1 JK
nat nip nepit nat equiv kB = 1380 650 5(23) times 10minus23 JK
bit shannon bit b Sh equiv ln(2) times kB = 9569 940 (16) times 10minus24 JK = 1 bit
ban hartley ban Hart equiv ln(10) times kB = 3179 065 3(53) times 10minus23 JK
nibble equiv 4 bits = 3827 976 0(64) times 10minus23 JK = 22 bit
byte B equiv 8 bits = 7655 952 (13) times 10minus23 JK = 23 bit
kilobyte (decimal) kB equiv 1 000 B = 7655 952 (13) times 10minus20 JK
kilobyte (kibibyte) KB KiB equiv 1 024 B = 7839 695 (13) times 10minus20 JK = 210 bit
Often information entropy is measured in shannons whereas the (discrete) storage space of digital devices ismeasured in bits Thus uncompressed redundant data occupy more than one bit of storage per shannon ofinformation entropy The multiples of a bit listed above are usually used with this meaning Other times the bit isused as a measure of information entropy and is thus a synonym of shannon
Luminous intensityThe candela is the preferred nomenclature for the SI unit
Luminous intensity
Name of unit Symbol Definition Relation toSI units
candela (SI baseunit) candle
cd The luminous intensity in a given direction of a source that emits monochromatic radiation offrequency 540 times 1012 hertz and that has a radiant intensity in that direction of 1683 watt persteradian[8]
= 1 cd
candlepower (new) cp equiv cd The use of candlepower as a unit is discouraged due to its ambiguity = 1 cd
candlepower (oldpre-1948)
cp Varies and is poorly reproducible[31] Approximately 0981 cd[14] asymp 0981 cd
Luminance
Conversion of units 25
Luminance
Name of unit Symbol Definition Relation to SI units
candela per square foot cdft2 equiv cdft2 asymp10763910417 cdm2
candela per square inch cdin2 equiv cdin2 asymp 15500031 cdm2
candela per square metre (SI unit) nit (deprecated[14] ) cdm2 equiv cdm2 = 1 cdm2
Name of unit Symbol Definition Relation to SI units
lumen (SIunit)
lm equiv cdmiddotsr = 1 lm = 1 cdmiddotsr
Illuminance
Illuminance
Name of unit Symbol Definition Relation to SI units
footcandle lumen per square foot fc equiv lmft2 = 10763910417 lx
lumen per square inch lmin2 equiv lmin2 asymp 15500031 lx
lux (SI unit) lx equiv lmm2 = 1 lx = 1 lmm2
phot (CGS unit) ph equiv lmcm2 = 1 times 104 lx
Radiation - source activity
Conversion of units 26
Radioactivity
Name of unit Symbol Definition Relation to SI units
becquerel (SIunit)
Bq equiv Number of disintegrations per second = 1 Bq = 1s
curie Ci equiv 37 times 1010 Bq = 37 times 1010 Bq [32]
rutherford (H) rd equiv 1 MBq = 1 times 106 Bq
Please note that although becquerel (Bq) and hertz (Hz) both ultimately refer to the same SI base unit (sminus1) Hz isused only for periodic phenomena and Bq is only used for stochastic processes associated with radioactivity[33]
Radiation - exposure
Radiation - exposure
Name of unit Symbol Definition Relation to SI units
roentgen R 1 R equiv 258 times 10minus4 Ckg[29] = 258 times 10minus4 Ckg
The roentgen is not a SI unit and the NIST strongly discourages its continued use[34]
Radiation - absorbed dose
Radiation - absorbed dose
Name of unit Symbol Definition Relation to SI units
Name of unit Symbol Definition Relation to SI units
Roumlntgen equivalent man rem equiv 001 Sv = 001 Sv
sievert (SI unit) Sv equiv 1 Jkg[33] = 1 Sv
Although the definitions for sievert (Sv) and gray (Gy) would seem to indicate that they measure the same quantitiesthis is not the case The effect of receiving a certain dose of radiation (given as Gy) is variable and depends on manyfactors thus a new unit was needed to denote the biological effectiveness of that dose on the body this is known asthe equivalent dose and is shown in Sv The general relationship between absorbed dose and equivalent dose can berepresented as
H = Q middot D
where H is the equivalent dose D is the absorbed dose and Q is a dimensionless quality factor Thus for anyquantity of D measured in Gy the numerical value for H measured in Sv may be different[36]
Conversion of units 27
Software toolsHome and office computers come with converters in bundled spreadsheet applications or can access free convertersvia the Internet Units and measurements can be easily converted using these tools but only if the units are explicitlydefined and the conversion is compatible (eg cmHg to kPa)
Free conversion softwarebull Units (software) a popular cross-platform command-line utilitybull Converter [37] contextual unit converter for Mozilla Firefox browsersbull Converber [38] portable application converting utilitybull calculla [39] calculla - online web convertersbull iMetrix [40] - unit converter for xpbull uniteasy [41] online scientific unit conversionbull Unit Converter Add-in for Excel [42] - allow a large selection of unit conversions within the Microsoft Excel
spread sheet programbull Unit Converter [43] simple and extensible unit converterbull Portable Unit Converter [44] including 4500 units 33 unit-categories and the possibility to create custom units
General commercial sources of convertersbull Advanced electronic calculators have unit-conversion functionalitybull Spreadsheet programs usually provide conversion functions or formulas or the user can write their ownbull Commercial mathematical scientific and technical applications often include converters
See also
bull Accuracy and precisionbull English unitsbull False precisionbull Imperial unitsbull International System of Unitsbull Mesures usuellesbull Metric system
bull Natural unitsbull Roundingbull Significant figuresbull Temperature conversionbull United States customary unitsbull Units conversion by factor-labelbull Units of measurement
External linksbull British law Units of measurement regulations 1995 [45]
bull ConvertBuster [46] Variety of conversion tools to convert easilybull How Many A dictionary of units of measurement [47]
bull NIST Fundamental physical constants mdash Non-SI units [48]PDF (357 KB)bull NIST Guide to SI Units [49] Many conversion factors listedbull Online Conversion Calculators [50] Very extensive list of conversions from-to equvalent unitsbull The Unified Code for Units of Measure [51]
bull Units Symbols and Conversions XML Dictionary [52]
bull Multilingual Online Conversion of Units [53]
bull Temperature Converter [54]
Conversion of units 28
References[1] United States Naval Observatory (2009) Selected Astronomical Constants 2009 (http asa usno navy mil SecK 2009
Astronomical_Constants_2009 txt) Accessed May 10 2009[2] NIST Reference on Constants Units and Uncertainty (http physics nist gov cgi-bin cuu Valuebohrrada0|search_for=Bohr+
radius)(2006) National Institute of Standards and Technology Retrieved February 22 2008[3] National Institute of Standards and Technology General Tables of Units of Measurement (http ts nist gov WeightsAndMeasures
Publications appxc cfm)[4] Lide D (Ed) (1990) Handbook of Chemistry and Physics (71st ed) Boca Raton FL CRC Press Section 1[5] National Bureau of Standards (June 30 1959) Refinement of values for the yard and the pound Federal Register viewed September 20
2006 at National Geodetic Survey web site (http www ngs noaa gov PUBS_LIB FedRegister FRdoc59-5442 pdf)[6] The International Astronomical Union and Astronomical Units (http www iau org public_press themes measuring )[7] Klein Herbert Arthur (1988) The Science of Measurement a Historical Survey Mineola NY Dover Publications 0-4862-5839-4[8] The International System of Units Section 21 (http www bipm org en si si_brochure chapter2 2-1 ) (8 ed) Bureau International des
Poids et Mesures 2006 retrieved August 26 2009[9] International System of Units (http www bipm org en si si_brochure chapter4 table8 html) 8th ed (2006) Bureau International des
Poids et Mesures Section 41 Table 8[10] P Kenneth Seidelmann Ed (1992) Explanatory Supplement to the Astronomical Almanac Sausalito CA University Science Books p 716
and sv parsec in Glossary[11] Whitelaw Ian (2007) A Measure of All Things The Story of Man and Measurement (http books google com
booksid=3zgGEWM5-iAC) New York Macmillan 0-312-37026-1 p 152[12] De Vinne Theodore Low (1900) The practice of typography a treatise on the processes of type-making the point system the names sizes
styles and prices of plain printing types (http books google com booksid=R4-DjphIpLMC) 2nd ed New York The Century Co p142ndash150
[13] Pasko Wesley Washington (1894) American dictionary of printing and bookmaking (http books google combooksid=Z_QUAAAAIAAJ) (1894) New York Howard Lockwood p 521
[14] Rowlett Russ (2005) How Many A Dictionary of Units of Measurement (http www unc edu ~rowlett units index html)[15] Thompson A and Taylor BN (2008) Guide for the Use of the International System of Units (SI) National Institute of Standards and
Technology Special Publication 811 p 57[16] US Code of Federal Regulations Title 21 Section 1019 Paragraph (b)(5)(viii) (http ecfr gpoaccess gov cgi t text text-idxc=ecframp
rgn=div8amp view=textamp node=212 0 1 1 2 1 1 6amp idno=21) retrieved August 29 2009[17] Barry N Taylor Ed NIST Special Publication 330 The International System of Units (SI) (http physics nist gov Pubs SP330 sp330
pdf) (2001 Edition) Washington US Government Printing Office 43The 12th Conference Generale des Poids et Mesures(CGPM)hellipdeclares that the word ldquolitrerdquo may be employed as a special name for the cubic decimetre
[18] CODATA Value atomic uint of mass (http physics nist gov cgi-bin cuu Valuettme|search_for=atomic+ unit+ of+ mass) (2006)National Institute of Standards and Technology Retrieved 16 September 2008
[19] The Swiss Federal Office for Metrology gives Zentner on a German language web page (http www metas ch de scales systemch html)and quintal on the English translation of that page (http www metas ch en scales systemch html) the unit is marked speacutecifiquementsuisse
[20] Pedersen O (1983) Glossary in Coyne G Hoskin M and Pedersen O Gregorian Reform of the Calendar Proceedings of the VaticanConference to Commemorate its 400th Anniversary Vatican Observatory Available from Astrophysics Data System
[21] Richards EG (1998) Mapping Time Oxford University Press pp 94ndash95 ISBN 0-19-850413-6[22] Steel Duncan (2000) Marking Time John Wiley amp Sons p 46 ISBN 0-471-29827-1[23] CODATA Value atomic unit of force (http physics nist gov cuu Constants ) (2006) National Institute of Standards and Technology
Retrieved September 14 2008[24] [[Comiteacute International des Poids et Mesures (http www bipm org en CIPM db 1946 2 )] Resolution 2] 1946 retrieved August 26
2009[25] Barry N Taylor (April 1995) Guide for the Use of the International System of Units (SI) (http physics nist gov cuu pdf sp811 pdf)
(NIST Special Publication 811) Washington DC US Government Printing Office pp 57ndash68[26] Barry N Taylor (April 1995) Guide for the Use of the International System of Units (SI) (NIST Special Publication 811) Washington DC
US Government Printing Office p 5[27] International System of Units (http www bipm org en si si_brochure chapter4 table7 html) 8th ed (2006) Bureau International des
Poids et Mesures Section 41 Table 7[28] The NIST Reference on Constants Units and Uncertainty (http physics nist gov cgi-bin cuu Valueauedm) 2006 retrieved August
26 2009[29] NIST Guide to SI Units Appendix B9 (http physics nist gov Pubs SP811 appenB9 html) retrieved August 27 2009[30] Standard for the Use of the International System of Units (SI) The Modern Metric System IEEEASTM SI 10-1997 (1997) New York and
West Conshohocken PA Institute of Electrical and Electronics Engineers and American Society for Testing and Materials Tables A1through A5
Conversion of units 29
[31] The NIST Reference on Constants Units and Uncertainty (http physics nist gov cuu Units candela html) retrieved August 28 2009[32] Ambler Thompson amp Barry N Taylor (2008) Guide for the Use of the International System of Units (SI) (http physics nist gov cuu
pdf sp811 pdf) Special Publication 811 Gaithersburg MD National Institute of Standards and Technology p 10[33] The International System of Units Section 222 Table 3 (http www bipm org en si si_brochure chapter2 2-2 table3 html) (8 ed)
Bureau International des Poids et Mesures 2006 retrieved August 27 2009[34] The NIST Guide to the SI (Special Publication 811) section 52 (http physics nist gov Pubs SP811 sec05 html5 2) 2008 retrieved
August 27 2009[35] Ambler Thompson amp Barry N Taylor (2008) Guide for the Use of the International System of Units (SI) (http physics nist gov cuu
pdf sp811 pdf) Special Publication 811 Gaithersburg MD National Institute of Standards and Technology p 5[36] [[Comiteacute international des poids et mesures (http www bipm org en CIPM db 2002 2 )] 2002 Recommendation 2] retrieved
August 27 2009[37] http converter mozdev org[38] http www xyntec com converber htm[39] http www calculla com[40] http illusions hu index phptask=100amp lang=0amp statpage=86[41] http www uniteasy com[42] http www tenderwire com wikipedialandingpage[43] http www kamlex com index phpoption=com_contentamp view=articleamp id=53amp Itemid=55[44] http www sttmedia com unitconverter[45] http www hmso gov uk si si1995 Uksi_19951804_en_2 htm[46] http www convertbuster com[47] http www unc edu ~rowlett units[48] http physics nist gov cuu Document nonsi_in_1998 pdf[49] http physics nist gov Pubs SP811 appenB9 html[50] http www onlineconversion com[51] http aurora rg iupui edu ~schadow units UCUM ucum html[52] http www posc org refs poscUnits20 xml[53] http www imperialtometric com[54] http www tampile com
Article Sources and Contributors 30
Article Sources and ContributorsConversion of units Source httpenwikipediaorgwindexphpoldid=373975089 Contributors 1571781xxx 7 A-giau AVSI Acather96 Ahoerstemeier Alexius08 Altenmann AndreEngels Andrewa Andy120290 Anonymi Ariconte Army1987 ArnoldReinhold Arthur3030 Aspects AxelBoldt AzaToth Azikala BW95 Bdesham Beland Bensaccount Bkumartvm Blackand White BlaiseFEgan BlueEarth Bobblewik Borbrav Bpmullins Bryan Derksen C J B Scholten CORNELIUSSEON CTZMSC3 Calltech Camerajohn Chaosfeary Charles MatthewsChris the speller Cmdrjameson Colonies Chris Conversion script Cope555 Crappy13 Crissov CyrilB DARTH SIDIOUS 2 DMacks DanielCD Dark Formal DarkestSideX DekisugiDenelson83 Dhp1080 Dicklyon DirkvdM Donald Duck Donarreiskoffer Dramatic Dyss DAringsbquougosz Egil Ehrenkater Ejohnsonboulder Elexmax Elf Emokhberi Enon Eob Epbr123Euchiasmus Fathead99 Father Goose Fella22 Femto FernandoAC Fibula Flutefreek Fred Bauder Fredrik Fuhghettaboutit Fuzheado Gaff Gene Nygaard Georgiy1996 Gerry AshtonGiftlite Gilliam Glenn L GoingBatty Goobergunch Gregsexton Greyengine5 Grunt Gurch Gutza HLHJ Haemo Hammersbach Heracles31 Herbee Heron HikerBush Hqb IcairnsIgiffin Indefatigable Isis JBobbitt JHunterJ Jabowery JakeVortex Jamicanmonkey Jason Begin Jay Jc3s5h Jcronen1 Jdoherty Jeffz1 Jeronimo Jimmuhk Jimp Jimwilliams57 JoeinwapJohndburger Josh Parris Jq4bagiq Kaihsu KaneWang Keenan Pepper Kevin Rector KeyStorm Khukri Kurtan Lee Daniel Crocker LightYear Linuxoidoz Liv4christ210 Loggie Lolo252Lupinelawyer M ichaeligl MJCdetroit MTC Mac MacMcF Magore Markus Kuhn Masterqwe MaxHund Maxamegalon2000 Mbeychok Meggar Mh26 Michael Daly Michael Hardy MichelAudy Mikelifeguard Mikhailov Kusserow Mindbuilder Missvain Monger Mr bulow MrOllie MrZhuKeeper Muro de Aguas Mwanner Mwtoews Nandesuka Natkeeran Ndsg NgjaimeNhy67ygv Nick Y Nick123 NickPenguin Ninjagecko Noe Nosilleg Now3r3 Obelix homologator Oldadamml Oleg Alexandrov Olivier Ortolan88 OwenBlacker Pac72 PassargeaPatrick Paul Martin Peter Horn Physchim62 Piels Pierdm Pmanderson Prometheus235 Quadell QuantumEleven Quod erat demonstrandum 314159 Radagast83 Rccoms RedWolfReinyday Revipm Rexparry sydney Reyk Rhetth Rhialto Rich Farmbrough Richard Myers Rjwilmsi Rlsheehan Robin Barry RoySmith Rpwolfgram SD6-Agent SGBailey SamuelLowry Samw Sander123 Seabhcan SebastianHelm Sherbert1 Shinhan Shrew Sietse Snel SimonP Sinbaddasail0r Skotte Smalljim SomeHuman Spencer Srleffler StarwarsmastergeekSteacoon StefanK SteveRamone Stevertigo Stokerm Suisui Sunev Superboy112233 Superm401 Synchronism Tacoman1996 Tarquin Taw Teratornis The Man in Question ThierrycThingg Thinking of England Thunderbird2 Timwi Tobias Hoevekamp Tomasr Tonsofpcs Toon05 Topsykretts2512 Trekphiler Tuwile Twanvl Uday147502 Unitman00 UrhixidurUtherSRG Vargenau Vsmith WarrenPlatts Wasell Welsh Whispering Wikinger Wolfkeeper Wtmitchell XJamRastafire Xenonice Yath Zginder Zibem Zocky Zotel 713 anonymousedits
Name of unit Symbol Definition Relation to SIunits
angular mil micro equiv 2π6400 rad asymp 0981 748 times 10minus3
rad
arcminute equiv 1deg60 asymp 0290 888 times 10minus3
rad
arcsecond equiv 1deg3600 asymp 4848 137 times 10minus6
rad
centesimal minuteof arc
equiv 1 grad100 asymp 0157 080 times 10minus3
rad
centesimal secondof arc
equiv 1 grad(10 000) asymp 1570 796 times 10minus6
rad
degree (of arc) deg equiv 1360 of a revolution equiv π180 rad asymp 17453293 times 10minus3 rad
grad gradian gon grad equiv 1400 of a revolution equiv 2π400 rad equiv 09deg asymp 15707963 times 10minus3 rad
octant equiv 45deg asymp 0785 398 rad
quadrant equiv 90deg asymp 1570 796 rad
radian (SI unit) rad The angle subtended at the center of a circle by an arc whose length is equal to the circlesradius One full revolution encompasses 2π radians
= 1 rad
sextant equiv 60deg asymp 1047 198 rad
sign equiv 30deg asymp 0523 599 rad
Conversion of units 10
Solid angle
Solid angle
Name of unit Symbol Definition Relation to SIunits
steradian (SIunit)
sr The solid angle subtended at the center of a sphere of radius r by a portion of the surface of the spherehaving an area r2 A sphere encompasses 4π sr[14]
= 1 sr
MassNotesbull See Weight for detail of massweight distinction and conversionbull In this table the unit gee is used to denote standard gravity in order to avoid confusion with the g symbol for
gramsbull In physics the pound of mass is sometimes written lbm to distinguish it from the pound-force (lbf) It should not
be read as the mongrel unit pound metre
Mass
Name of unit Symbol Definition Relation to SI units
atomic mass unit unified u AMU asymp 1660 538 73 times 10minus27 plusmn 13 times 10minus36 kg
atomic unit of mass electron restmass
me asymp 9109 382 15 times 10minus31 plusmn 45 times 10minus39 kg[18]
bag (coffee) equiv 60 kg = 60 kg
bag (Portland cement) equiv 94 lb av = 42637 682 78 kg
barge equiv 22frac12 sh tn = 20 411656 65 kg
carat kt equiv 3 16 gr asymp 205196 548 333 mg
carat (metric) ct equiv 200 mg = 200 mg
clove equiv 8 lb av = 3628 738 96 kg
crith asymp 899349 mg
dalton Da asymp 1660 902 10 times 10minus27 plusmn 13 times 10minus36 kg
dram (apothecary troy) dr t equiv 60 gr = 3887 9346 g
dram (avoirdupois) dr av equiv 27 1132 gr = 1771 845 195 3125 g
electronvolt eV equiv 1 eV (energy unit) c2 = 17826 times 10minus36 kg
gamma γ equiv 1 μg = 1 μg
grain gr equiv 17000 lb av equiv 64798 91 mg
grave G grave was the original name of the kilogram equiv 1 kg
hundredweight (long) long cwt orcwt
equiv 112 lb av = 50802 345 44 kg
hundredweight (short) cental sh cwt equiv 100 lb av = 45359 237 kg
hyl (CGS unit) equiv 1 gee times 1 g times 1 s2m = 9806 65 g
hyl (MKS unit) equiv 1 gee times 1 kg times 1 s2m = 9806 65 kg
Conversion of units 11
kilogram kg equiv mass of the prototype near Paris (asymp mass of 1L ofwater)
equiv 1 kg (SI base unit)[8]
kip kip equiv 1000 lb av = 453592 37 kg
mark equiv 8 oz t = 248827 8144 g
mite equiv 120 gr = 3239 9455 mg
mite (metric) equiv 120 g = 50 mg
ounce (apothecary troy) oz t equiv 112 lb t = 31103 4768 g
ounce (avoirdupois) oz av equiv 116 lb = 28349 523 125 g
ounce (US food nutritionlabeling)
oz equiv 28 g[16] = 28 g
pennyweight dwt pwt equiv 120 oz t = 1555 173 84 g
point equiv 1100 ct = 2 mg
pound (avoirdupois) lb av equiv 0453 592 37 kg = 7000 grains equiv 0453 592 37 kg
pound (metric) equiv 500 g = 500 g
pound (troy) lb t equiv 5 760 grains = 0373 241 7216 kg
quarter (Imperial) equiv 14 long cwt = 2 st = 28 lb av = 12700 586 36 kg
quarter (informal) equiv frac14 short tn = 226796 185 kg
quarter long (informal) equiv frac14 long tn = 254011 7272 kg
quintal (metric) q equiv 100 kg = 100 kg
scruple (apothecary) s ap equiv 20 gr = 1295 9782 g
sheet equiv 1700 lb av = 6479891 mg
slug geepound slug equiv 1 gee times 1 lb av times 1 s2ft asymp 14593 903 kg
stone st equiv 14 lb av = 6350 293 18 kg
ton assay (long) AT equiv 1 mg times 1 long tn divide 1 oz t asymp 32666 667 g
ton assay (short) AT equiv 1 mg times 1 sh tn divide 1 oz t asymp 29166 667 g
ton long long tn or ton equiv 2 240 lb = 1 016046 9088 kg
ton short sh tn equiv 2 000 lb = 907184 74 kg
tonne (mts unit) t equiv 1 000 kg = 1 000 kg
wey equiv 252 lb = 18 st = 114305 277 24 kg (variants exist)
Zentner Ztr Definitions vary see [19] and[14]
Density
Conversion of units 12
Density
Name of unit Symbol Definition Relation to SI units
gram per millilitre gmL equiv gmL = 1000 kgm3
kilogram per cubic metre (SI unit) kgm3 equiv kgm3 = 1 kgm3
slug per cubic foot slugft3 equiv slugft3 asymp 5153788184 kgm3
Time
Time t
Name of unit Symbol Definition Relation to SI units
atomic unit of time au equiv a0(αmiddotc) asymp 2418 884 254 times 10minus17
s
Callippic cycle equiv 441 mo (hollow) + 499 mo (full) = 76 a of 36525 d = 2398 3776 times 109 s
century c equiv 100 a (see below for definition of year length) = 100 times year
day d = 24 h = 86400 s
day (sidereal) d equiv Time needed for the Earth to rotate once around its axisdetermined from successive transits of a very distantastronomical object across an observers meridian(International Celestial Reference Frame)
asymp 86 1641 s
decade dec equiv 10 a (see below for definition of year length) = 10 times year
fortnight fn equiv 2 wk = 1 209 600 s
helek equiv 11 080 h = 33 s
Hipparchic cycle equiv 4 Callippic cycles - 1 d = 9593 424 times 109 s
hour h equiv 60 min = 3 600 s
jiffy j equiv 160 s = 016 s
jiffy (alternate) ja equiv 1100 s = 10 ms
ke (quarter of an hour) equiv frac14 h = 196 d = 60 times 60 4 s = 900 s= 60 4 min = 15 min
Conversion of units 13
ke (traditional) equiv 1100 d = 24 times 60 times 60 100 s =864 s = 24 60 100min = 144 min
lustre lustrum equiv 5 a of 365 d = 15768 times 108 s
Metonic cycle enneadecaeteris equiv 110 mo (hollow) + 125 mo (full) = 6940 d asymp 19 a = 5996 16 times 108 s
millennium equiv 1 000 a (see below for definition of year length) = 1000 times year
milliday md equiv 11 000 d = 24 times 60 times 60 1 000 s= 864 s
minute min equiv 60 s due to leap seconds sometimes 59 s or 61 s = 60 s
moment equiv 90 s = 90 s
month (full) mo equiv 30 d[20] = 2 592 000 s
month (Greg av) mo Average Gregorian month = 365242512 d = 30436875 d asymp 26297 times 106 s
month (hollow) mo equiv 29 d[20] = 2 505 600 s
month (synodic) mo Cycle time of moon phases asymp 29530589 days (Average) asymp 2551 times 106 s
octaeteris = 48 mo (full) + 48 mo (hollow) + 3 mo (full)[21] [22] = 8 aof 36525 d = 2922 d
= 2524 608 times 108 s
Planck time equiv (Gℏc5)frac12 asymp 1351 211 868 times 10minus43
s
second s time of 9 192 631 770 periods of the radiation correspondingto the transition between the 2 hyperfine levels of the groundstate of the caesium 133 atom at 0 K[8] (but other secondsare sometimes used in astronomy)
(SI base unit)
shake equiv 10minus8 s = 10 ns
sigma equiv 10minus6 s = 1 μs
Sothic cycle equiv 1 461 a of 365 d = 4607 4096 times 1010 s
svedberg S equiv 10minus13 s = 100 fs
week wk equiv 7 d = 604 800 s
year (Gregorian) a y oryr
= 3652425 d average calculated from common years (365d) plus leap years (366 d) on most years divisible by 4 Seeleap year for details
= 31 556 952 s
year (Julian) a y oryr
= 36525 d average calculated from common years (365 d)plus one leap year (366 d) every four years
= 31 557 600 s
year (sidereal) a y oryr
equiv time taken for Sun to return to the same position withrespect to the stars of the celestial sphere
asymp 365256 363 d asymp 31558 1497632 s
year (tropical) a y oryr
equiv Length of time it takes for the Sun to return to the sameposition in the cycle of seasons
asymp 365242 190 d asymp 31556 925 s
Where UTC is observed the length of timeunits longer than 1 s may increase or decreaseby 1 s if a leap second occurs during the timeinterval of interest
Conversion of units 14
Frequency
Frequency
Name of unit Symbol Definition Relation to SI units
hertz (SI unit) Hz equiv Number of cycles per second = 1 Hz = 1s
revolutions per minute rpm equiv One unit rpm equals one rotation completed around a fixed axis in one minute of time asymp0104719755 rads
Speed or velocity
Speed
Name of unit Symbol Definition Relation to SI units
foot per hour fph equiv 1 fth asymp 8466 667 times 10minus5
ms
foot per minute fpm equiv 1 ftmin = 508 times 10minus3 ms
foot per second fps equiv 1 fts = 3048 times 10minus1 ms
furlong perfortnight
equiv furlongfortnight asymp 1663 095 times 10minus4
ms
inch per minute ipm equiv 1 inmin asymp 423 333 times 10minus4 ms
inch per second ips equiv 1 ins = 254 times 10minus2 ms
mach number M Ratio of the speed to the speed of sound in the medium Varies especially with temperatureAbout 761 mph (1225 kph) in air at sea level to about 660 mph (1062 kph) at jet altitudesUnitless
asymp 340 to 295 ms foraircraft
metre per second(SI unit)
ms equiv 1 ms = 1 ms
mile per hour mph equiv 1 mih = 0447 04 ms
mile per minute mpm equiv 1 mimin = 268224 ms
mile per second mps equiv 1 mis = 1 609344 ms
speed of light invacuum
c equiv 299 792 458 ms = 299 792 458 ms
speed of sound inair
s Varies especially with temperature About 761 mph (1225 kph) in air at sea level to about660 mph (1062 kph) at jet altitudes
asymp 340 to 295 ms ataircraft altitudes
A velocity consists of a speed combined with a direction the speed part of the velocity takes units of speed
Conversion of units 15
Flow (volume)
Flow
Name of unit Symbol Definition Relation to SI units
cubic foot per minute CFM equiv 1 ft3min = 4719474432 times 10minus4 m3s
cubic foot per second ft3s equiv 1 ft3s = 0028316846592 m3s
cubic inch per minute in3min equiv 1 in3min = 27311773 times 10minus7 m3s
cubic inch per second in3s equiv 1 in3s = 16387064 times 10minus5 m3s
cubic metre per second (SIunit)
m3s equiv 1 m3s = 1 m3s
gallon (US fluid) per day GPD equiv 1 gald = 4381263638 times 10minus8 m3s
gallon (US fluid) per hour GPH equiv 1 galh = 1051503273 times 10minus6 m3s
gallon (US fluid) per minute GPM equiv 1 galmin = 630901964 times 10minus5 m3s
litre per minute LPM equiv 1 Lmin = 16 times 10minus5 m3s
Acceleration
Acceleration
Name of unit Symbol Definition Relation to SI units
foot per hour per second fphs equiv 1 ft(hmiddots) asymp 8466 667 times 10minus5
ms2
foot per minute per second fpms equiv 1 ft(minmiddots) = 508 times 10minus3 ms2
foot per second squared fps2 equiv 1 fts2 = 3048 times 10minus1 ms2
gal galileo Gal equiv 1 cms2 = 10minus2 ms2
inch per minute per second ipms equiv 1 in(minmiddots) asymp 4233 333 times 10minus4
ms2
inch per second squared ips2 equiv 1 ins2 = 254 times 10minus2 ms2
knot per second kns equiv 1 kns asymp 5144 444 times 10minus1
ms2
metre per second squared (SI unit) ms2 equiv 1 ms2 = 1 ms2
mile per hour per second mphs equiv 1 mi(hmiddots) = 44704 times 10minus1 ms2
mile per minute per second mpms equiv 1 mi(minmiddots) = 268224 ms2
mile per second squared mps2 equiv 1 mis2 = 1609 344 times 103 ms2
standard gravity g equiv 9806 65 ms2 = 9806 65 ms2
Conversion of units 16
Force
Force
Name of unit Symbol Definition Relation to SI units
atomic unit of force equiv memiddotα2middotc2a0 asymp 8238 722 06 times 10minus8 N
[23]
dyne (cgs unit) dyn equiv gmiddotcms2 = 10minus5 N
kilogram-force kilopondgrave-force
kgf kp Gf equiv g times 1 kg = 9806 65 N
kip kip-force kip kipfklbf
equiv g times 1 000 lb = 4448 221 6152605 times 103 N
milligrave-force gravet-force mGf gf equiv g times 1 g = 9806 65 mN
newton (SI unit) N A force capable of giving a mass of one kg an acceleration of one metreper second per second[24]
= 1 N = 1 kgmiddotms2
ounce-force ozf equiv g times 1 oz = 0278 013 850 9537812 N
pound lb equiv slugmiddotfts2 = 4448 230 531 N
pound-force lbf equiv g times 1 lb = 4448 221 615 2605 N
poise (cgs unit) P equiv 10minus1 Pamiddots = 01 Pamiddots
pound per foot hour lb(ftmiddoth) equiv 1 lb(ftmiddoth) asymp 4133 789 times 10minus4 Pamiddots
pound per foot second lb(ftmiddots) equiv 1 lb(ftmiddots) asymp 1488164 Pamiddots
pound-force second per square foot lbfmiddotsft2 equiv 1 lbfmiddotsft2 asymp 4788026 Pamiddots
pound-force second per square inch lbfmiddotsin2 equiv 1 lbfmiddotsin2 asymp 6894757 Pamiddots
Conversion of units 21
Kinematic viscosity
Kinematic viscosity
Name of unit Symbol Definition Relation to SI units
square foot per second ft2s equiv 1 ft2s = 009290304 m2s
square metre per second (SI unit) m2s equiv 1 m2s = 1 m2s
stokes (cgs unit) St equiv10minus4 m2s
= 10minus4 m2s
Electric current
Electric current
Name of unit Symbol Definition Relation to SI units
ampere (SI base unit) A equiv The constant current needed to produce a force of 2 times 10minus7 newton per metre betweentwo straight parallel conductors of infinite length and negligible circular cross-sectionplaced one metre apart in a vacuum[8]
= 1 A
electromagnetic unitabampere (cgs unit)
abamp equiv 10 A = 10 A
esu per secondstatampere (cgs unit)
esus equiv (01 Amiddotms) c asymp3335641 times 10minus10 A
Electric charge
Electric charge
Name of unit Symbol Definition Relation to SI units
abcoulomb electromagnetic unit (cgsunit)
abC emu equiv 10 C = 10 C
atomic unit of charge au equiv e asymp 1602 176462 times 10minus19 C
coulomb (SI unit) C equiv The amount of electricity carried in one second of time by oneampere of current[24]
= 1 C = 1 Amiddots
faraday F equiv 1 mol times NAmiddote asymp 96 4853383 C
statcoulomb franklin electrostatic unit(cgs unit)
statC Fresu
equiv (01 Amiddotm) c asymp 3335 641 times 10minus10 C
Conversion of units 22
Electric dipole
Electric dipole
Name of unit Symbol Definition Relation to SI units
atomic unit of electric dipole moment ea0 asymp 8478 352 81 times 10minus30
Cmiddotm[28]
Electromotive force electric potential difference
Voltage electromotive force
Name ofunit
Symbol Definition Relation to SI units
abvolt (cgsunit)
abV equiv 1 times 10minus8 V = 1 times 10minus8 V
statvolt (cgsunit)
statV equiv cmiddot (1 μJAmiddotm) = 299792 458 V
volt (SIunit)
V The difference in electric potential across two points along a conducting wire carrying one ampereof constant current when the power dissipated between the points equals one watt[24]
= 1 V = 1 WA = 1kgmiddotm2(Amiddots3)
Electrical resistance
Electrical resistance
Name ofunit
Symbol Definition Relation to SI units
ohm (SIunit)
Ω The resistance between two points in a conductor when one volt of electric potential differenceapplied to these points produces one ampere of current in the conductor[24]
= 1 Ω = 1 VA = 1kgmiddotm2(A2middots3)
Capacitance
Capacitors ability to store charge
Name ofunit
Symbol Definition Relation to SI units
farad (SIunit)
F The capacitance between two parallel plates that results in one volt of potential difference whencharged by one coulomb of electricity[24]
= 1 F = 1 CV = 1A2middots4(kgmiddotm2)
Conversion of units 23
Magnetic flux
magnetic flux
Name of unit Symbol Definition Relation to SI units
maxwell (CGSunit)
Mx equiv 10minus8 Wb[29] = 1 times 10minus8 Wb
weber (SIunit)
Wb Magnetic flux which linking a circuit of one turn would produce in it an electromotive force of1 volt if it were reduced to zero at a uniform rate in 1 second[24]
= 1 Wb = 1 Vmiddots = 1kgmiddotm2(Amiddots2)
Magnetic flux density
What physicists call Magnetic field is called Magnetic flux density by electrical engineersand magnetic induction by applied mathematicians and electrical engineers
Name of unit Symbol Definition Relation to SI units
gauss (CGS unit) G equiv Mxcm2 = 10minus4
T= 1 times 10minus4 T [30]
tesla (SI unit) T equiv Wbm2 = 1 T = 1 Wbm2 = 1kg(Amiddots2)
Inductance
Inductance
Name ofunit
Symbol Definition Relation to SI units
henry (SIunit)
H The inductance of a closed circuit that produces one volt of electromotive force when the current inthe circuit varies at a uniform rate of one ampere per second[24]
= 1 H = 1 WbA = 1kgmiddotm2(Amiddots)2
Temperature
Temperature
Name of unit Symbol Definition Conversion to kelvin
degree Celsius degC degC equiv K minus 27315 [K] equiv [degC] + 27315
degree Delisle degDe [K] = 37315 minus [degDe] times 23
degree Fahrenheit degF degF equiv degC times 95 + 32 [K] equiv ([degF] + 45967) times 59
degree Newton degN [K] = [degN] times 10033 + 27315
degree Rankine degR degRa degR equiv K times 95 [K] equiv [degR] times 59
degree Reacuteaumur degReacute [K] = [degReacute] times 54 + 27315
degree Roslashmer degRoslash [K] = ([degRoslash] minus 75) times 4021 + 27315
kelvin (SI baseunit)
K equiv 127316 of the thermodynamic temperature of the triple point of water[8] equiv 1 K
Conversion of units 24
Information entropy
Information entropy
Name of unit Symbol Definition Relation to SI units Relation to bits
SI unit JK equiv JK = 1 JK
nat nip nepit nat equiv kB = 1380 650 5(23) times 10minus23 JK
bit shannon bit b Sh equiv ln(2) times kB = 9569 940 (16) times 10minus24 JK = 1 bit
ban hartley ban Hart equiv ln(10) times kB = 3179 065 3(53) times 10minus23 JK
nibble equiv 4 bits = 3827 976 0(64) times 10minus23 JK = 22 bit
byte B equiv 8 bits = 7655 952 (13) times 10minus23 JK = 23 bit
kilobyte (decimal) kB equiv 1 000 B = 7655 952 (13) times 10minus20 JK
kilobyte (kibibyte) KB KiB equiv 1 024 B = 7839 695 (13) times 10minus20 JK = 210 bit
Often information entropy is measured in shannons whereas the (discrete) storage space of digital devices ismeasured in bits Thus uncompressed redundant data occupy more than one bit of storage per shannon ofinformation entropy The multiples of a bit listed above are usually used with this meaning Other times the bit isused as a measure of information entropy and is thus a synonym of shannon
Luminous intensityThe candela is the preferred nomenclature for the SI unit
Luminous intensity
Name of unit Symbol Definition Relation toSI units
candela (SI baseunit) candle
cd The luminous intensity in a given direction of a source that emits monochromatic radiation offrequency 540 times 1012 hertz and that has a radiant intensity in that direction of 1683 watt persteradian[8]
= 1 cd
candlepower (new) cp equiv cd The use of candlepower as a unit is discouraged due to its ambiguity = 1 cd
candlepower (oldpre-1948)
cp Varies and is poorly reproducible[31] Approximately 0981 cd[14] asymp 0981 cd
Luminance
Conversion of units 25
Luminance
Name of unit Symbol Definition Relation to SI units
candela per square foot cdft2 equiv cdft2 asymp10763910417 cdm2
candela per square inch cdin2 equiv cdin2 asymp 15500031 cdm2
candela per square metre (SI unit) nit (deprecated[14] ) cdm2 equiv cdm2 = 1 cdm2
Name of unit Symbol Definition Relation to SI units
lumen (SIunit)
lm equiv cdmiddotsr = 1 lm = 1 cdmiddotsr
Illuminance
Illuminance
Name of unit Symbol Definition Relation to SI units
footcandle lumen per square foot fc equiv lmft2 = 10763910417 lx
lumen per square inch lmin2 equiv lmin2 asymp 15500031 lx
lux (SI unit) lx equiv lmm2 = 1 lx = 1 lmm2
phot (CGS unit) ph equiv lmcm2 = 1 times 104 lx
Radiation - source activity
Conversion of units 26
Radioactivity
Name of unit Symbol Definition Relation to SI units
becquerel (SIunit)
Bq equiv Number of disintegrations per second = 1 Bq = 1s
curie Ci equiv 37 times 1010 Bq = 37 times 1010 Bq [32]
rutherford (H) rd equiv 1 MBq = 1 times 106 Bq
Please note that although becquerel (Bq) and hertz (Hz) both ultimately refer to the same SI base unit (sminus1) Hz isused only for periodic phenomena and Bq is only used for stochastic processes associated with radioactivity[33]
Radiation - exposure
Radiation - exposure
Name of unit Symbol Definition Relation to SI units
roentgen R 1 R equiv 258 times 10minus4 Ckg[29] = 258 times 10minus4 Ckg
The roentgen is not a SI unit and the NIST strongly discourages its continued use[34]
Radiation - absorbed dose
Radiation - absorbed dose
Name of unit Symbol Definition Relation to SI units
Name of unit Symbol Definition Relation to SI units
Roumlntgen equivalent man rem equiv 001 Sv = 001 Sv
sievert (SI unit) Sv equiv 1 Jkg[33] = 1 Sv
Although the definitions for sievert (Sv) and gray (Gy) would seem to indicate that they measure the same quantitiesthis is not the case The effect of receiving a certain dose of radiation (given as Gy) is variable and depends on manyfactors thus a new unit was needed to denote the biological effectiveness of that dose on the body this is known asthe equivalent dose and is shown in Sv The general relationship between absorbed dose and equivalent dose can berepresented as
H = Q middot D
where H is the equivalent dose D is the absorbed dose and Q is a dimensionless quality factor Thus for anyquantity of D measured in Gy the numerical value for H measured in Sv may be different[36]
Conversion of units 27
Software toolsHome and office computers come with converters in bundled spreadsheet applications or can access free convertersvia the Internet Units and measurements can be easily converted using these tools but only if the units are explicitlydefined and the conversion is compatible (eg cmHg to kPa)
Free conversion softwarebull Units (software) a popular cross-platform command-line utilitybull Converter [37] contextual unit converter for Mozilla Firefox browsersbull Converber [38] portable application converting utilitybull calculla [39] calculla - online web convertersbull iMetrix [40] - unit converter for xpbull uniteasy [41] online scientific unit conversionbull Unit Converter Add-in for Excel [42] - allow a large selection of unit conversions within the Microsoft Excel
spread sheet programbull Unit Converter [43] simple and extensible unit converterbull Portable Unit Converter [44] including 4500 units 33 unit-categories and the possibility to create custom units
General commercial sources of convertersbull Advanced electronic calculators have unit-conversion functionalitybull Spreadsheet programs usually provide conversion functions or formulas or the user can write their ownbull Commercial mathematical scientific and technical applications often include converters
See also
bull Accuracy and precisionbull English unitsbull False precisionbull Imperial unitsbull International System of Unitsbull Mesures usuellesbull Metric system
bull Natural unitsbull Roundingbull Significant figuresbull Temperature conversionbull United States customary unitsbull Units conversion by factor-labelbull Units of measurement
External linksbull British law Units of measurement regulations 1995 [45]
bull ConvertBuster [46] Variety of conversion tools to convert easilybull How Many A dictionary of units of measurement [47]
bull NIST Fundamental physical constants mdash Non-SI units [48]PDF (357 KB)bull NIST Guide to SI Units [49] Many conversion factors listedbull Online Conversion Calculators [50] Very extensive list of conversions from-to equvalent unitsbull The Unified Code for Units of Measure [51]
bull Units Symbols and Conversions XML Dictionary [52]
bull Multilingual Online Conversion of Units [53]
bull Temperature Converter [54]
Conversion of units 28
References[1] United States Naval Observatory (2009) Selected Astronomical Constants 2009 (http asa usno navy mil SecK 2009
Astronomical_Constants_2009 txt) Accessed May 10 2009[2] NIST Reference on Constants Units and Uncertainty (http physics nist gov cgi-bin cuu Valuebohrrada0|search_for=Bohr+
radius)(2006) National Institute of Standards and Technology Retrieved February 22 2008[3] National Institute of Standards and Technology General Tables of Units of Measurement (http ts nist gov WeightsAndMeasures
Publications appxc cfm)[4] Lide D (Ed) (1990) Handbook of Chemistry and Physics (71st ed) Boca Raton FL CRC Press Section 1[5] National Bureau of Standards (June 30 1959) Refinement of values for the yard and the pound Federal Register viewed September 20
2006 at National Geodetic Survey web site (http www ngs noaa gov PUBS_LIB FedRegister FRdoc59-5442 pdf)[6] The International Astronomical Union and Astronomical Units (http www iau org public_press themes measuring )[7] Klein Herbert Arthur (1988) The Science of Measurement a Historical Survey Mineola NY Dover Publications 0-4862-5839-4[8] The International System of Units Section 21 (http www bipm org en si si_brochure chapter2 2-1 ) (8 ed) Bureau International des
Poids et Mesures 2006 retrieved August 26 2009[9] International System of Units (http www bipm org en si si_brochure chapter4 table8 html) 8th ed (2006) Bureau International des
Poids et Mesures Section 41 Table 8[10] P Kenneth Seidelmann Ed (1992) Explanatory Supplement to the Astronomical Almanac Sausalito CA University Science Books p 716
and sv parsec in Glossary[11] Whitelaw Ian (2007) A Measure of All Things The Story of Man and Measurement (http books google com
booksid=3zgGEWM5-iAC) New York Macmillan 0-312-37026-1 p 152[12] De Vinne Theodore Low (1900) The practice of typography a treatise on the processes of type-making the point system the names sizes
styles and prices of plain printing types (http books google com booksid=R4-DjphIpLMC) 2nd ed New York The Century Co p142ndash150
[13] Pasko Wesley Washington (1894) American dictionary of printing and bookmaking (http books google combooksid=Z_QUAAAAIAAJ) (1894) New York Howard Lockwood p 521
[14] Rowlett Russ (2005) How Many A Dictionary of Units of Measurement (http www unc edu ~rowlett units index html)[15] Thompson A and Taylor BN (2008) Guide for the Use of the International System of Units (SI) National Institute of Standards and
Technology Special Publication 811 p 57[16] US Code of Federal Regulations Title 21 Section 1019 Paragraph (b)(5)(viii) (http ecfr gpoaccess gov cgi t text text-idxc=ecframp
rgn=div8amp view=textamp node=212 0 1 1 2 1 1 6amp idno=21) retrieved August 29 2009[17] Barry N Taylor Ed NIST Special Publication 330 The International System of Units (SI) (http physics nist gov Pubs SP330 sp330
pdf) (2001 Edition) Washington US Government Printing Office 43The 12th Conference Generale des Poids et Mesures(CGPM)hellipdeclares that the word ldquolitrerdquo may be employed as a special name for the cubic decimetre
[18] CODATA Value atomic uint of mass (http physics nist gov cgi-bin cuu Valuettme|search_for=atomic+ unit+ of+ mass) (2006)National Institute of Standards and Technology Retrieved 16 September 2008
[19] The Swiss Federal Office for Metrology gives Zentner on a German language web page (http www metas ch de scales systemch html)and quintal on the English translation of that page (http www metas ch en scales systemch html) the unit is marked speacutecifiquementsuisse
[20] Pedersen O (1983) Glossary in Coyne G Hoskin M and Pedersen O Gregorian Reform of the Calendar Proceedings of the VaticanConference to Commemorate its 400th Anniversary Vatican Observatory Available from Astrophysics Data System
[21] Richards EG (1998) Mapping Time Oxford University Press pp 94ndash95 ISBN 0-19-850413-6[22] Steel Duncan (2000) Marking Time John Wiley amp Sons p 46 ISBN 0-471-29827-1[23] CODATA Value atomic unit of force (http physics nist gov cuu Constants ) (2006) National Institute of Standards and Technology
Retrieved September 14 2008[24] [[Comiteacute International des Poids et Mesures (http www bipm org en CIPM db 1946 2 )] Resolution 2] 1946 retrieved August 26
2009[25] Barry N Taylor (April 1995) Guide for the Use of the International System of Units (SI) (http physics nist gov cuu pdf sp811 pdf)
(NIST Special Publication 811) Washington DC US Government Printing Office pp 57ndash68[26] Barry N Taylor (April 1995) Guide for the Use of the International System of Units (SI) (NIST Special Publication 811) Washington DC
US Government Printing Office p 5[27] International System of Units (http www bipm org en si si_brochure chapter4 table7 html) 8th ed (2006) Bureau International des
Poids et Mesures Section 41 Table 7[28] The NIST Reference on Constants Units and Uncertainty (http physics nist gov cgi-bin cuu Valueauedm) 2006 retrieved August
26 2009[29] NIST Guide to SI Units Appendix B9 (http physics nist gov Pubs SP811 appenB9 html) retrieved August 27 2009[30] Standard for the Use of the International System of Units (SI) The Modern Metric System IEEEASTM SI 10-1997 (1997) New York and
West Conshohocken PA Institute of Electrical and Electronics Engineers and American Society for Testing and Materials Tables A1through A5
Conversion of units 29
[31] The NIST Reference on Constants Units and Uncertainty (http physics nist gov cuu Units candela html) retrieved August 28 2009[32] Ambler Thompson amp Barry N Taylor (2008) Guide for the Use of the International System of Units (SI) (http physics nist gov cuu
pdf sp811 pdf) Special Publication 811 Gaithersburg MD National Institute of Standards and Technology p 10[33] The International System of Units Section 222 Table 3 (http www bipm org en si si_brochure chapter2 2-2 table3 html) (8 ed)
Bureau International des Poids et Mesures 2006 retrieved August 27 2009[34] The NIST Guide to the SI (Special Publication 811) section 52 (http physics nist gov Pubs SP811 sec05 html5 2) 2008 retrieved
August 27 2009[35] Ambler Thompson amp Barry N Taylor (2008) Guide for the Use of the International System of Units (SI) (http physics nist gov cuu
pdf sp811 pdf) Special Publication 811 Gaithersburg MD National Institute of Standards and Technology p 5[36] [[Comiteacute international des poids et mesures (http www bipm org en CIPM db 2002 2 )] 2002 Recommendation 2] retrieved
August 27 2009[37] http converter mozdev org[38] http www xyntec com converber htm[39] http www calculla com[40] http illusions hu index phptask=100amp lang=0amp statpage=86[41] http www uniteasy com[42] http www tenderwire com wikipedialandingpage[43] http www kamlex com index phpoption=com_contentamp view=articleamp id=53amp Itemid=55[44] http www sttmedia com unitconverter[45] http www hmso gov uk si si1995 Uksi_19951804_en_2 htm[46] http www convertbuster com[47] http www unc edu ~rowlett units[48] http physics nist gov cuu Document nonsi_in_1998 pdf[49] http physics nist gov Pubs SP811 appenB9 html[50] http www onlineconversion com[51] http aurora rg iupui edu ~schadow units UCUM ucum html[52] http www posc org refs poscUnits20 xml[53] http www imperialtometric com[54] http www tampile com
Article Sources and Contributors 30
Article Sources and ContributorsConversion of units Source httpenwikipediaorgwindexphpoldid=373975089 Contributors 1571781xxx 7 A-giau AVSI Acather96 Ahoerstemeier Alexius08 Altenmann AndreEngels Andrewa Andy120290 Anonymi Ariconte Army1987 ArnoldReinhold Arthur3030 Aspects AxelBoldt AzaToth Azikala BW95 Bdesham Beland Bensaccount Bkumartvm Blackand White BlaiseFEgan BlueEarth Bobblewik Borbrav Bpmullins Bryan Derksen C J B Scholten CORNELIUSSEON CTZMSC3 Calltech Camerajohn Chaosfeary Charles MatthewsChris the speller Cmdrjameson Colonies Chris Conversion script Cope555 Crappy13 Crissov CyrilB DARTH SIDIOUS 2 DMacks DanielCD Dark Formal DarkestSideX DekisugiDenelson83 Dhp1080 Dicklyon DirkvdM Donald Duck Donarreiskoffer Dramatic Dyss DAringsbquougosz Egil Ehrenkater Ejohnsonboulder Elexmax Elf Emokhberi Enon Eob Epbr123Euchiasmus Fathead99 Father Goose Fella22 Femto FernandoAC Fibula Flutefreek Fred Bauder Fredrik Fuhghettaboutit Fuzheado Gaff Gene Nygaard Georgiy1996 Gerry AshtonGiftlite Gilliam Glenn L GoingBatty Goobergunch Gregsexton Greyengine5 Grunt Gurch Gutza HLHJ Haemo Hammersbach Heracles31 Herbee Heron HikerBush Hqb IcairnsIgiffin Indefatigable Isis JBobbitt JHunterJ Jabowery JakeVortex Jamicanmonkey Jason Begin Jay Jc3s5h Jcronen1 Jdoherty Jeffz1 Jeronimo Jimmuhk Jimp Jimwilliams57 JoeinwapJohndburger Josh Parris Jq4bagiq Kaihsu KaneWang Keenan Pepper Kevin Rector KeyStorm Khukri Kurtan Lee Daniel Crocker LightYear Linuxoidoz Liv4christ210 Loggie Lolo252Lupinelawyer M ichaeligl MJCdetroit MTC Mac MacMcF Magore Markus Kuhn Masterqwe MaxHund Maxamegalon2000 Mbeychok Meggar Mh26 Michael Daly Michael Hardy MichelAudy Mikelifeguard Mikhailov Kusserow Mindbuilder Missvain Monger Mr bulow MrOllie MrZhuKeeper Muro de Aguas Mwanner Mwtoews Nandesuka Natkeeran Ndsg NgjaimeNhy67ygv Nick Y Nick123 NickPenguin Ninjagecko Noe Nosilleg Now3r3 Obelix homologator Oldadamml Oleg Alexandrov Olivier Ortolan88 OwenBlacker Pac72 PassargeaPatrick Paul Martin Peter Horn Physchim62 Piels Pierdm Pmanderson Prometheus235 Quadell QuantumEleven Quod erat demonstrandum 314159 Radagast83 Rccoms RedWolfReinyday Revipm Rexparry sydney Reyk Rhetth Rhialto Rich Farmbrough Richard Myers Rjwilmsi Rlsheehan Robin Barry RoySmith Rpwolfgram SD6-Agent SGBailey SamuelLowry Samw Sander123 Seabhcan SebastianHelm Sherbert1 Shinhan Shrew Sietse Snel SimonP Sinbaddasail0r Skotte Smalljim SomeHuman Spencer Srleffler StarwarsmastergeekSteacoon StefanK SteveRamone Stevertigo Stokerm Suisui Sunev Superboy112233 Superm401 Synchronism Tacoman1996 Tarquin Taw Teratornis The Man in Question ThierrycThingg Thinking of England Thunderbird2 Timwi Tobias Hoevekamp Tomasr Tonsofpcs Toon05 Topsykretts2512 Trekphiler Tuwile Twanvl Uday147502 Unitman00 UrhixidurUtherSRG Vargenau Vsmith WarrenPlatts Wasell Welsh Whispering Wikinger Wolfkeeper Wtmitchell XJamRastafire Xenonice Yath Zginder Zibem Zocky Zotel 713 anonymousedits
Name of unit Symbol Definition Relation to SIunits
angular mil micro equiv 2π6400 rad asymp 0981 748 times 10minus3
rad
arcminute equiv 1deg60 asymp 0290 888 times 10minus3
rad
arcsecond equiv 1deg3600 asymp 4848 137 times 10minus6
rad
centesimal minuteof arc
equiv 1 grad100 asymp 0157 080 times 10minus3
rad
centesimal secondof arc
equiv 1 grad(10 000) asymp 1570 796 times 10minus6
rad
degree (of arc) deg equiv 1360 of a revolution equiv π180 rad asymp 17453293 times 10minus3 rad
grad gradian gon grad equiv 1400 of a revolution equiv 2π400 rad equiv 09deg asymp 15707963 times 10minus3 rad
octant equiv 45deg asymp 0785 398 rad
quadrant equiv 90deg asymp 1570 796 rad
radian (SI unit) rad The angle subtended at the center of a circle by an arc whose length is equal to the circlesradius One full revolution encompasses 2π radians
= 1 rad
sextant equiv 60deg asymp 1047 198 rad
sign equiv 30deg asymp 0523 599 rad
Conversion of units 10
Solid angle
Solid angle
Name of unit Symbol Definition Relation to SIunits
steradian (SIunit)
sr The solid angle subtended at the center of a sphere of radius r by a portion of the surface of the spherehaving an area r2 A sphere encompasses 4π sr[14]
= 1 sr
MassNotesbull See Weight for detail of massweight distinction and conversionbull In this table the unit gee is used to denote standard gravity in order to avoid confusion with the g symbol for
gramsbull In physics the pound of mass is sometimes written lbm to distinguish it from the pound-force (lbf) It should not
be read as the mongrel unit pound metre
Mass
Name of unit Symbol Definition Relation to SI units
atomic mass unit unified u AMU asymp 1660 538 73 times 10minus27 plusmn 13 times 10minus36 kg
atomic unit of mass electron restmass
me asymp 9109 382 15 times 10minus31 plusmn 45 times 10minus39 kg[18]
bag (coffee) equiv 60 kg = 60 kg
bag (Portland cement) equiv 94 lb av = 42637 682 78 kg
barge equiv 22frac12 sh tn = 20 411656 65 kg
carat kt equiv 3 16 gr asymp 205196 548 333 mg
carat (metric) ct equiv 200 mg = 200 mg
clove equiv 8 lb av = 3628 738 96 kg
crith asymp 899349 mg
dalton Da asymp 1660 902 10 times 10minus27 plusmn 13 times 10minus36 kg
dram (apothecary troy) dr t equiv 60 gr = 3887 9346 g
dram (avoirdupois) dr av equiv 27 1132 gr = 1771 845 195 3125 g
electronvolt eV equiv 1 eV (energy unit) c2 = 17826 times 10minus36 kg
gamma γ equiv 1 μg = 1 μg
grain gr equiv 17000 lb av equiv 64798 91 mg
grave G grave was the original name of the kilogram equiv 1 kg
hundredweight (long) long cwt orcwt
equiv 112 lb av = 50802 345 44 kg
hundredweight (short) cental sh cwt equiv 100 lb av = 45359 237 kg
hyl (CGS unit) equiv 1 gee times 1 g times 1 s2m = 9806 65 g
hyl (MKS unit) equiv 1 gee times 1 kg times 1 s2m = 9806 65 kg
Conversion of units 11
kilogram kg equiv mass of the prototype near Paris (asymp mass of 1L ofwater)
equiv 1 kg (SI base unit)[8]
kip kip equiv 1000 lb av = 453592 37 kg
mark equiv 8 oz t = 248827 8144 g
mite equiv 120 gr = 3239 9455 mg
mite (metric) equiv 120 g = 50 mg
ounce (apothecary troy) oz t equiv 112 lb t = 31103 4768 g
ounce (avoirdupois) oz av equiv 116 lb = 28349 523 125 g
ounce (US food nutritionlabeling)
oz equiv 28 g[16] = 28 g
pennyweight dwt pwt equiv 120 oz t = 1555 173 84 g
point equiv 1100 ct = 2 mg
pound (avoirdupois) lb av equiv 0453 592 37 kg = 7000 grains equiv 0453 592 37 kg
pound (metric) equiv 500 g = 500 g
pound (troy) lb t equiv 5 760 grains = 0373 241 7216 kg
quarter (Imperial) equiv 14 long cwt = 2 st = 28 lb av = 12700 586 36 kg
quarter (informal) equiv frac14 short tn = 226796 185 kg
quarter long (informal) equiv frac14 long tn = 254011 7272 kg
quintal (metric) q equiv 100 kg = 100 kg
scruple (apothecary) s ap equiv 20 gr = 1295 9782 g
sheet equiv 1700 lb av = 6479891 mg
slug geepound slug equiv 1 gee times 1 lb av times 1 s2ft asymp 14593 903 kg
stone st equiv 14 lb av = 6350 293 18 kg
ton assay (long) AT equiv 1 mg times 1 long tn divide 1 oz t asymp 32666 667 g
ton assay (short) AT equiv 1 mg times 1 sh tn divide 1 oz t asymp 29166 667 g
ton long long tn or ton equiv 2 240 lb = 1 016046 9088 kg
ton short sh tn equiv 2 000 lb = 907184 74 kg
tonne (mts unit) t equiv 1 000 kg = 1 000 kg
wey equiv 252 lb = 18 st = 114305 277 24 kg (variants exist)
Zentner Ztr Definitions vary see [19] and[14]
Density
Conversion of units 12
Density
Name of unit Symbol Definition Relation to SI units
gram per millilitre gmL equiv gmL = 1000 kgm3
kilogram per cubic metre (SI unit) kgm3 equiv kgm3 = 1 kgm3
slug per cubic foot slugft3 equiv slugft3 asymp 5153788184 kgm3
Time
Time t
Name of unit Symbol Definition Relation to SI units
atomic unit of time au equiv a0(αmiddotc) asymp 2418 884 254 times 10minus17
s
Callippic cycle equiv 441 mo (hollow) + 499 mo (full) = 76 a of 36525 d = 2398 3776 times 109 s
century c equiv 100 a (see below for definition of year length) = 100 times year
day d = 24 h = 86400 s
day (sidereal) d equiv Time needed for the Earth to rotate once around its axisdetermined from successive transits of a very distantastronomical object across an observers meridian(International Celestial Reference Frame)
asymp 86 1641 s
decade dec equiv 10 a (see below for definition of year length) = 10 times year
fortnight fn equiv 2 wk = 1 209 600 s
helek equiv 11 080 h = 33 s
Hipparchic cycle equiv 4 Callippic cycles - 1 d = 9593 424 times 109 s
hour h equiv 60 min = 3 600 s
jiffy j equiv 160 s = 016 s
jiffy (alternate) ja equiv 1100 s = 10 ms
ke (quarter of an hour) equiv frac14 h = 196 d = 60 times 60 4 s = 900 s= 60 4 min = 15 min
Conversion of units 13
ke (traditional) equiv 1100 d = 24 times 60 times 60 100 s =864 s = 24 60 100min = 144 min
lustre lustrum equiv 5 a of 365 d = 15768 times 108 s
Metonic cycle enneadecaeteris equiv 110 mo (hollow) + 125 mo (full) = 6940 d asymp 19 a = 5996 16 times 108 s
millennium equiv 1 000 a (see below for definition of year length) = 1000 times year
milliday md equiv 11 000 d = 24 times 60 times 60 1 000 s= 864 s
minute min equiv 60 s due to leap seconds sometimes 59 s or 61 s = 60 s
moment equiv 90 s = 90 s
month (full) mo equiv 30 d[20] = 2 592 000 s
month (Greg av) mo Average Gregorian month = 365242512 d = 30436875 d asymp 26297 times 106 s
month (hollow) mo equiv 29 d[20] = 2 505 600 s
month (synodic) mo Cycle time of moon phases asymp 29530589 days (Average) asymp 2551 times 106 s
octaeteris = 48 mo (full) + 48 mo (hollow) + 3 mo (full)[21] [22] = 8 aof 36525 d = 2922 d
= 2524 608 times 108 s
Planck time equiv (Gℏc5)frac12 asymp 1351 211 868 times 10minus43
s
second s time of 9 192 631 770 periods of the radiation correspondingto the transition between the 2 hyperfine levels of the groundstate of the caesium 133 atom at 0 K[8] (but other secondsare sometimes used in astronomy)
(SI base unit)
shake equiv 10minus8 s = 10 ns
sigma equiv 10minus6 s = 1 μs
Sothic cycle equiv 1 461 a of 365 d = 4607 4096 times 1010 s
svedberg S equiv 10minus13 s = 100 fs
week wk equiv 7 d = 604 800 s
year (Gregorian) a y oryr
= 3652425 d average calculated from common years (365d) plus leap years (366 d) on most years divisible by 4 Seeleap year for details
= 31 556 952 s
year (Julian) a y oryr
= 36525 d average calculated from common years (365 d)plus one leap year (366 d) every four years
= 31 557 600 s
year (sidereal) a y oryr
equiv time taken for Sun to return to the same position withrespect to the stars of the celestial sphere
asymp 365256 363 d asymp 31558 1497632 s
year (tropical) a y oryr
equiv Length of time it takes for the Sun to return to the sameposition in the cycle of seasons
asymp 365242 190 d asymp 31556 925 s
Where UTC is observed the length of timeunits longer than 1 s may increase or decreaseby 1 s if a leap second occurs during the timeinterval of interest
Conversion of units 14
Frequency
Frequency
Name of unit Symbol Definition Relation to SI units
hertz (SI unit) Hz equiv Number of cycles per second = 1 Hz = 1s
revolutions per minute rpm equiv One unit rpm equals one rotation completed around a fixed axis in one minute of time asymp0104719755 rads
Speed or velocity
Speed
Name of unit Symbol Definition Relation to SI units
foot per hour fph equiv 1 fth asymp 8466 667 times 10minus5
ms
foot per minute fpm equiv 1 ftmin = 508 times 10minus3 ms
foot per second fps equiv 1 fts = 3048 times 10minus1 ms
furlong perfortnight
equiv furlongfortnight asymp 1663 095 times 10minus4
ms
inch per minute ipm equiv 1 inmin asymp 423 333 times 10minus4 ms
inch per second ips equiv 1 ins = 254 times 10minus2 ms
mach number M Ratio of the speed to the speed of sound in the medium Varies especially with temperatureAbout 761 mph (1225 kph) in air at sea level to about 660 mph (1062 kph) at jet altitudesUnitless
asymp 340 to 295 ms foraircraft
metre per second(SI unit)
ms equiv 1 ms = 1 ms
mile per hour mph equiv 1 mih = 0447 04 ms
mile per minute mpm equiv 1 mimin = 268224 ms
mile per second mps equiv 1 mis = 1 609344 ms
speed of light invacuum
c equiv 299 792 458 ms = 299 792 458 ms
speed of sound inair
s Varies especially with temperature About 761 mph (1225 kph) in air at sea level to about660 mph (1062 kph) at jet altitudes
asymp 340 to 295 ms ataircraft altitudes
A velocity consists of a speed combined with a direction the speed part of the velocity takes units of speed
Conversion of units 15
Flow (volume)
Flow
Name of unit Symbol Definition Relation to SI units
cubic foot per minute CFM equiv 1 ft3min = 4719474432 times 10minus4 m3s
cubic foot per second ft3s equiv 1 ft3s = 0028316846592 m3s
cubic inch per minute in3min equiv 1 in3min = 27311773 times 10minus7 m3s
cubic inch per second in3s equiv 1 in3s = 16387064 times 10minus5 m3s
cubic metre per second (SIunit)
m3s equiv 1 m3s = 1 m3s
gallon (US fluid) per day GPD equiv 1 gald = 4381263638 times 10minus8 m3s
gallon (US fluid) per hour GPH equiv 1 galh = 1051503273 times 10minus6 m3s
gallon (US fluid) per minute GPM equiv 1 galmin = 630901964 times 10minus5 m3s
litre per minute LPM equiv 1 Lmin = 16 times 10minus5 m3s
Acceleration
Acceleration
Name of unit Symbol Definition Relation to SI units
foot per hour per second fphs equiv 1 ft(hmiddots) asymp 8466 667 times 10minus5
ms2
foot per minute per second fpms equiv 1 ft(minmiddots) = 508 times 10minus3 ms2
foot per second squared fps2 equiv 1 fts2 = 3048 times 10minus1 ms2
gal galileo Gal equiv 1 cms2 = 10minus2 ms2
inch per minute per second ipms equiv 1 in(minmiddots) asymp 4233 333 times 10minus4
ms2
inch per second squared ips2 equiv 1 ins2 = 254 times 10minus2 ms2
knot per second kns equiv 1 kns asymp 5144 444 times 10minus1
ms2
metre per second squared (SI unit) ms2 equiv 1 ms2 = 1 ms2
mile per hour per second mphs equiv 1 mi(hmiddots) = 44704 times 10minus1 ms2
mile per minute per second mpms equiv 1 mi(minmiddots) = 268224 ms2
mile per second squared mps2 equiv 1 mis2 = 1609 344 times 103 ms2
standard gravity g equiv 9806 65 ms2 = 9806 65 ms2
Conversion of units 16
Force
Force
Name of unit Symbol Definition Relation to SI units
atomic unit of force equiv memiddotα2middotc2a0 asymp 8238 722 06 times 10minus8 N
[23]
dyne (cgs unit) dyn equiv gmiddotcms2 = 10minus5 N
kilogram-force kilopondgrave-force
kgf kp Gf equiv g times 1 kg = 9806 65 N
kip kip-force kip kipfklbf
equiv g times 1 000 lb = 4448 221 6152605 times 103 N
milligrave-force gravet-force mGf gf equiv g times 1 g = 9806 65 mN
newton (SI unit) N A force capable of giving a mass of one kg an acceleration of one metreper second per second[24]
= 1 N = 1 kgmiddotms2
ounce-force ozf equiv g times 1 oz = 0278 013 850 9537812 N
pound lb equiv slugmiddotfts2 = 4448 230 531 N
pound-force lbf equiv g times 1 lb = 4448 221 615 2605 N
poise (cgs unit) P equiv 10minus1 Pamiddots = 01 Pamiddots
pound per foot hour lb(ftmiddoth) equiv 1 lb(ftmiddoth) asymp 4133 789 times 10minus4 Pamiddots
pound per foot second lb(ftmiddots) equiv 1 lb(ftmiddots) asymp 1488164 Pamiddots
pound-force second per square foot lbfmiddotsft2 equiv 1 lbfmiddotsft2 asymp 4788026 Pamiddots
pound-force second per square inch lbfmiddotsin2 equiv 1 lbfmiddotsin2 asymp 6894757 Pamiddots
Conversion of units 21
Kinematic viscosity
Kinematic viscosity
Name of unit Symbol Definition Relation to SI units
square foot per second ft2s equiv 1 ft2s = 009290304 m2s
square metre per second (SI unit) m2s equiv 1 m2s = 1 m2s
stokes (cgs unit) St equiv10minus4 m2s
= 10minus4 m2s
Electric current
Electric current
Name of unit Symbol Definition Relation to SI units
ampere (SI base unit) A equiv The constant current needed to produce a force of 2 times 10minus7 newton per metre betweentwo straight parallel conductors of infinite length and negligible circular cross-sectionplaced one metre apart in a vacuum[8]
= 1 A
electromagnetic unitabampere (cgs unit)
abamp equiv 10 A = 10 A
esu per secondstatampere (cgs unit)
esus equiv (01 Amiddotms) c asymp3335641 times 10minus10 A
Electric charge
Electric charge
Name of unit Symbol Definition Relation to SI units
abcoulomb electromagnetic unit (cgsunit)
abC emu equiv 10 C = 10 C
atomic unit of charge au equiv e asymp 1602 176462 times 10minus19 C
coulomb (SI unit) C equiv The amount of electricity carried in one second of time by oneampere of current[24]
= 1 C = 1 Amiddots
faraday F equiv 1 mol times NAmiddote asymp 96 4853383 C
statcoulomb franklin electrostatic unit(cgs unit)
statC Fresu
equiv (01 Amiddotm) c asymp 3335 641 times 10minus10 C
Conversion of units 22
Electric dipole
Electric dipole
Name of unit Symbol Definition Relation to SI units
atomic unit of electric dipole moment ea0 asymp 8478 352 81 times 10minus30
Cmiddotm[28]
Electromotive force electric potential difference
Voltage electromotive force
Name ofunit
Symbol Definition Relation to SI units
abvolt (cgsunit)
abV equiv 1 times 10minus8 V = 1 times 10minus8 V
statvolt (cgsunit)
statV equiv cmiddot (1 μJAmiddotm) = 299792 458 V
volt (SIunit)
V The difference in electric potential across two points along a conducting wire carrying one ampereof constant current when the power dissipated between the points equals one watt[24]
= 1 V = 1 WA = 1kgmiddotm2(Amiddots3)
Electrical resistance
Electrical resistance
Name ofunit
Symbol Definition Relation to SI units
ohm (SIunit)
Ω The resistance between two points in a conductor when one volt of electric potential differenceapplied to these points produces one ampere of current in the conductor[24]
= 1 Ω = 1 VA = 1kgmiddotm2(A2middots3)
Capacitance
Capacitors ability to store charge
Name ofunit
Symbol Definition Relation to SI units
farad (SIunit)
F The capacitance between two parallel plates that results in one volt of potential difference whencharged by one coulomb of electricity[24]
= 1 F = 1 CV = 1A2middots4(kgmiddotm2)
Conversion of units 23
Magnetic flux
magnetic flux
Name of unit Symbol Definition Relation to SI units
maxwell (CGSunit)
Mx equiv 10minus8 Wb[29] = 1 times 10minus8 Wb
weber (SIunit)
Wb Magnetic flux which linking a circuit of one turn would produce in it an electromotive force of1 volt if it were reduced to zero at a uniform rate in 1 second[24]
= 1 Wb = 1 Vmiddots = 1kgmiddotm2(Amiddots2)
Magnetic flux density
What physicists call Magnetic field is called Magnetic flux density by electrical engineersand magnetic induction by applied mathematicians and electrical engineers
Name of unit Symbol Definition Relation to SI units
gauss (CGS unit) G equiv Mxcm2 = 10minus4
T= 1 times 10minus4 T [30]
tesla (SI unit) T equiv Wbm2 = 1 T = 1 Wbm2 = 1kg(Amiddots2)
Inductance
Inductance
Name ofunit
Symbol Definition Relation to SI units
henry (SIunit)
H The inductance of a closed circuit that produces one volt of electromotive force when the current inthe circuit varies at a uniform rate of one ampere per second[24]
= 1 H = 1 WbA = 1kgmiddotm2(Amiddots)2
Temperature
Temperature
Name of unit Symbol Definition Conversion to kelvin
degree Celsius degC degC equiv K minus 27315 [K] equiv [degC] + 27315
degree Delisle degDe [K] = 37315 minus [degDe] times 23
degree Fahrenheit degF degF equiv degC times 95 + 32 [K] equiv ([degF] + 45967) times 59
degree Newton degN [K] = [degN] times 10033 + 27315
degree Rankine degR degRa degR equiv K times 95 [K] equiv [degR] times 59
degree Reacuteaumur degReacute [K] = [degReacute] times 54 + 27315
degree Roslashmer degRoslash [K] = ([degRoslash] minus 75) times 4021 + 27315
kelvin (SI baseunit)
K equiv 127316 of the thermodynamic temperature of the triple point of water[8] equiv 1 K
Conversion of units 24
Information entropy
Information entropy
Name of unit Symbol Definition Relation to SI units Relation to bits
SI unit JK equiv JK = 1 JK
nat nip nepit nat equiv kB = 1380 650 5(23) times 10minus23 JK
bit shannon bit b Sh equiv ln(2) times kB = 9569 940 (16) times 10minus24 JK = 1 bit
ban hartley ban Hart equiv ln(10) times kB = 3179 065 3(53) times 10minus23 JK
nibble equiv 4 bits = 3827 976 0(64) times 10minus23 JK = 22 bit
byte B equiv 8 bits = 7655 952 (13) times 10minus23 JK = 23 bit
kilobyte (decimal) kB equiv 1 000 B = 7655 952 (13) times 10minus20 JK
kilobyte (kibibyte) KB KiB equiv 1 024 B = 7839 695 (13) times 10minus20 JK = 210 bit
Often information entropy is measured in shannons whereas the (discrete) storage space of digital devices ismeasured in bits Thus uncompressed redundant data occupy more than one bit of storage per shannon ofinformation entropy The multiples of a bit listed above are usually used with this meaning Other times the bit isused as a measure of information entropy and is thus a synonym of shannon
Luminous intensityThe candela is the preferred nomenclature for the SI unit
Luminous intensity
Name of unit Symbol Definition Relation toSI units
candela (SI baseunit) candle
cd The luminous intensity in a given direction of a source that emits monochromatic radiation offrequency 540 times 1012 hertz and that has a radiant intensity in that direction of 1683 watt persteradian[8]
= 1 cd
candlepower (new) cp equiv cd The use of candlepower as a unit is discouraged due to its ambiguity = 1 cd
candlepower (oldpre-1948)
cp Varies and is poorly reproducible[31] Approximately 0981 cd[14] asymp 0981 cd
Luminance
Conversion of units 25
Luminance
Name of unit Symbol Definition Relation to SI units
candela per square foot cdft2 equiv cdft2 asymp10763910417 cdm2
candela per square inch cdin2 equiv cdin2 asymp 15500031 cdm2
candela per square metre (SI unit) nit (deprecated[14] ) cdm2 equiv cdm2 = 1 cdm2
Name of unit Symbol Definition Relation to SI units
lumen (SIunit)
lm equiv cdmiddotsr = 1 lm = 1 cdmiddotsr
Illuminance
Illuminance
Name of unit Symbol Definition Relation to SI units
footcandle lumen per square foot fc equiv lmft2 = 10763910417 lx
lumen per square inch lmin2 equiv lmin2 asymp 15500031 lx
lux (SI unit) lx equiv lmm2 = 1 lx = 1 lmm2
phot (CGS unit) ph equiv lmcm2 = 1 times 104 lx
Radiation - source activity
Conversion of units 26
Radioactivity
Name of unit Symbol Definition Relation to SI units
becquerel (SIunit)
Bq equiv Number of disintegrations per second = 1 Bq = 1s
curie Ci equiv 37 times 1010 Bq = 37 times 1010 Bq [32]
rutherford (H) rd equiv 1 MBq = 1 times 106 Bq
Please note that although becquerel (Bq) and hertz (Hz) both ultimately refer to the same SI base unit (sminus1) Hz isused only for periodic phenomena and Bq is only used for stochastic processes associated with radioactivity[33]
Radiation - exposure
Radiation - exposure
Name of unit Symbol Definition Relation to SI units
roentgen R 1 R equiv 258 times 10minus4 Ckg[29] = 258 times 10minus4 Ckg
The roentgen is not a SI unit and the NIST strongly discourages its continued use[34]
Radiation - absorbed dose
Radiation - absorbed dose
Name of unit Symbol Definition Relation to SI units
Name of unit Symbol Definition Relation to SI units
Roumlntgen equivalent man rem equiv 001 Sv = 001 Sv
sievert (SI unit) Sv equiv 1 Jkg[33] = 1 Sv
Although the definitions for sievert (Sv) and gray (Gy) would seem to indicate that they measure the same quantitiesthis is not the case The effect of receiving a certain dose of radiation (given as Gy) is variable and depends on manyfactors thus a new unit was needed to denote the biological effectiveness of that dose on the body this is known asthe equivalent dose and is shown in Sv The general relationship between absorbed dose and equivalent dose can berepresented as
H = Q middot D
where H is the equivalent dose D is the absorbed dose and Q is a dimensionless quality factor Thus for anyquantity of D measured in Gy the numerical value for H measured in Sv may be different[36]
Conversion of units 27
Software toolsHome and office computers come with converters in bundled spreadsheet applications or can access free convertersvia the Internet Units and measurements can be easily converted using these tools but only if the units are explicitlydefined and the conversion is compatible (eg cmHg to kPa)
Free conversion softwarebull Units (software) a popular cross-platform command-line utilitybull Converter [37] contextual unit converter for Mozilla Firefox browsersbull Converber [38] portable application converting utilitybull calculla [39] calculla - online web convertersbull iMetrix [40] - unit converter for xpbull uniteasy [41] online scientific unit conversionbull Unit Converter Add-in for Excel [42] - allow a large selection of unit conversions within the Microsoft Excel
spread sheet programbull Unit Converter [43] simple and extensible unit converterbull Portable Unit Converter [44] including 4500 units 33 unit-categories and the possibility to create custom units
General commercial sources of convertersbull Advanced electronic calculators have unit-conversion functionalitybull Spreadsheet programs usually provide conversion functions or formulas or the user can write their ownbull Commercial mathematical scientific and technical applications often include converters
See also
bull Accuracy and precisionbull English unitsbull False precisionbull Imperial unitsbull International System of Unitsbull Mesures usuellesbull Metric system
bull Natural unitsbull Roundingbull Significant figuresbull Temperature conversionbull United States customary unitsbull Units conversion by factor-labelbull Units of measurement
External linksbull British law Units of measurement regulations 1995 [45]
bull ConvertBuster [46] Variety of conversion tools to convert easilybull How Many A dictionary of units of measurement [47]
bull NIST Fundamental physical constants mdash Non-SI units [48]PDF (357 KB)bull NIST Guide to SI Units [49] Many conversion factors listedbull Online Conversion Calculators [50] Very extensive list of conversions from-to equvalent unitsbull The Unified Code for Units of Measure [51]
bull Units Symbols and Conversions XML Dictionary [52]
bull Multilingual Online Conversion of Units [53]
bull Temperature Converter [54]
Conversion of units 28
References[1] United States Naval Observatory (2009) Selected Astronomical Constants 2009 (http asa usno navy mil SecK 2009
Astronomical_Constants_2009 txt) Accessed May 10 2009[2] NIST Reference on Constants Units and Uncertainty (http physics nist gov cgi-bin cuu Valuebohrrada0|search_for=Bohr+
radius)(2006) National Institute of Standards and Technology Retrieved February 22 2008[3] National Institute of Standards and Technology General Tables of Units of Measurement (http ts nist gov WeightsAndMeasures
Publications appxc cfm)[4] Lide D (Ed) (1990) Handbook of Chemistry and Physics (71st ed) Boca Raton FL CRC Press Section 1[5] National Bureau of Standards (June 30 1959) Refinement of values for the yard and the pound Federal Register viewed September 20
2006 at National Geodetic Survey web site (http www ngs noaa gov PUBS_LIB FedRegister FRdoc59-5442 pdf)[6] The International Astronomical Union and Astronomical Units (http www iau org public_press themes measuring )[7] Klein Herbert Arthur (1988) The Science of Measurement a Historical Survey Mineola NY Dover Publications 0-4862-5839-4[8] The International System of Units Section 21 (http www bipm org en si si_brochure chapter2 2-1 ) (8 ed) Bureau International des
Poids et Mesures 2006 retrieved August 26 2009[9] International System of Units (http www bipm org en si si_brochure chapter4 table8 html) 8th ed (2006) Bureau International des
Poids et Mesures Section 41 Table 8[10] P Kenneth Seidelmann Ed (1992) Explanatory Supplement to the Astronomical Almanac Sausalito CA University Science Books p 716
and sv parsec in Glossary[11] Whitelaw Ian (2007) A Measure of All Things The Story of Man and Measurement (http books google com
booksid=3zgGEWM5-iAC) New York Macmillan 0-312-37026-1 p 152[12] De Vinne Theodore Low (1900) The practice of typography a treatise on the processes of type-making the point system the names sizes
styles and prices of plain printing types (http books google com booksid=R4-DjphIpLMC) 2nd ed New York The Century Co p142ndash150
[13] Pasko Wesley Washington (1894) American dictionary of printing and bookmaking (http books google combooksid=Z_QUAAAAIAAJ) (1894) New York Howard Lockwood p 521
[14] Rowlett Russ (2005) How Many A Dictionary of Units of Measurement (http www unc edu ~rowlett units index html)[15] Thompson A and Taylor BN (2008) Guide for the Use of the International System of Units (SI) National Institute of Standards and
Technology Special Publication 811 p 57[16] US Code of Federal Regulations Title 21 Section 1019 Paragraph (b)(5)(viii) (http ecfr gpoaccess gov cgi t text text-idxc=ecframp
rgn=div8amp view=textamp node=212 0 1 1 2 1 1 6amp idno=21) retrieved August 29 2009[17] Barry N Taylor Ed NIST Special Publication 330 The International System of Units (SI) (http physics nist gov Pubs SP330 sp330
pdf) (2001 Edition) Washington US Government Printing Office 43The 12th Conference Generale des Poids et Mesures(CGPM)hellipdeclares that the word ldquolitrerdquo may be employed as a special name for the cubic decimetre
[18] CODATA Value atomic uint of mass (http physics nist gov cgi-bin cuu Valuettme|search_for=atomic+ unit+ of+ mass) (2006)National Institute of Standards and Technology Retrieved 16 September 2008
[19] The Swiss Federal Office for Metrology gives Zentner on a German language web page (http www metas ch de scales systemch html)and quintal on the English translation of that page (http www metas ch en scales systemch html) the unit is marked speacutecifiquementsuisse
[20] Pedersen O (1983) Glossary in Coyne G Hoskin M and Pedersen O Gregorian Reform of the Calendar Proceedings of the VaticanConference to Commemorate its 400th Anniversary Vatican Observatory Available from Astrophysics Data System
[21] Richards EG (1998) Mapping Time Oxford University Press pp 94ndash95 ISBN 0-19-850413-6[22] Steel Duncan (2000) Marking Time John Wiley amp Sons p 46 ISBN 0-471-29827-1[23] CODATA Value atomic unit of force (http physics nist gov cuu Constants ) (2006) National Institute of Standards and Technology
Retrieved September 14 2008[24] [[Comiteacute International des Poids et Mesures (http www bipm org en CIPM db 1946 2 )] Resolution 2] 1946 retrieved August 26
2009[25] Barry N Taylor (April 1995) Guide for the Use of the International System of Units (SI) (http physics nist gov cuu pdf sp811 pdf)
(NIST Special Publication 811) Washington DC US Government Printing Office pp 57ndash68[26] Barry N Taylor (April 1995) Guide for the Use of the International System of Units (SI) (NIST Special Publication 811) Washington DC
US Government Printing Office p 5[27] International System of Units (http www bipm org en si si_brochure chapter4 table7 html) 8th ed (2006) Bureau International des
Poids et Mesures Section 41 Table 7[28] The NIST Reference on Constants Units and Uncertainty (http physics nist gov cgi-bin cuu Valueauedm) 2006 retrieved August
26 2009[29] NIST Guide to SI Units Appendix B9 (http physics nist gov Pubs SP811 appenB9 html) retrieved August 27 2009[30] Standard for the Use of the International System of Units (SI) The Modern Metric System IEEEASTM SI 10-1997 (1997) New York and
West Conshohocken PA Institute of Electrical and Electronics Engineers and American Society for Testing and Materials Tables A1through A5
Conversion of units 29
[31] The NIST Reference on Constants Units and Uncertainty (http physics nist gov cuu Units candela html) retrieved August 28 2009[32] Ambler Thompson amp Barry N Taylor (2008) Guide for the Use of the International System of Units (SI) (http physics nist gov cuu
pdf sp811 pdf) Special Publication 811 Gaithersburg MD National Institute of Standards and Technology p 10[33] The International System of Units Section 222 Table 3 (http www bipm org en si si_brochure chapter2 2-2 table3 html) (8 ed)
Bureau International des Poids et Mesures 2006 retrieved August 27 2009[34] The NIST Guide to the SI (Special Publication 811) section 52 (http physics nist gov Pubs SP811 sec05 html5 2) 2008 retrieved
August 27 2009[35] Ambler Thompson amp Barry N Taylor (2008) Guide for the Use of the International System of Units (SI) (http physics nist gov cuu
pdf sp811 pdf) Special Publication 811 Gaithersburg MD National Institute of Standards and Technology p 5[36] [[Comiteacute international des poids et mesures (http www bipm org en CIPM db 2002 2 )] 2002 Recommendation 2] retrieved
August 27 2009[37] http converter mozdev org[38] http www xyntec com converber htm[39] http www calculla com[40] http illusions hu index phptask=100amp lang=0amp statpage=86[41] http www uniteasy com[42] http www tenderwire com wikipedialandingpage[43] http www kamlex com index phpoption=com_contentamp view=articleamp id=53amp Itemid=55[44] http www sttmedia com unitconverter[45] http www hmso gov uk si si1995 Uksi_19951804_en_2 htm[46] http www convertbuster com[47] http www unc edu ~rowlett units[48] http physics nist gov cuu Document nonsi_in_1998 pdf[49] http physics nist gov Pubs SP811 appenB9 html[50] http www onlineconversion com[51] http aurora rg iupui edu ~schadow units UCUM ucum html[52] http www posc org refs poscUnits20 xml[53] http www imperialtometric com[54] http www tampile com
Article Sources and Contributors 30
Article Sources and ContributorsConversion of units Source httpenwikipediaorgwindexphpoldid=373975089 Contributors 1571781xxx 7 A-giau AVSI Acather96 Ahoerstemeier Alexius08 Altenmann AndreEngels Andrewa Andy120290 Anonymi Ariconte Army1987 ArnoldReinhold Arthur3030 Aspects AxelBoldt AzaToth Azikala BW95 Bdesham Beland Bensaccount Bkumartvm Blackand White BlaiseFEgan BlueEarth Bobblewik Borbrav Bpmullins Bryan Derksen C J B Scholten CORNELIUSSEON CTZMSC3 Calltech Camerajohn Chaosfeary Charles MatthewsChris the speller Cmdrjameson Colonies Chris Conversion script Cope555 Crappy13 Crissov CyrilB DARTH SIDIOUS 2 DMacks DanielCD Dark Formal DarkestSideX DekisugiDenelson83 Dhp1080 Dicklyon DirkvdM Donald Duck Donarreiskoffer Dramatic Dyss DAringsbquougosz Egil Ehrenkater Ejohnsonboulder Elexmax Elf Emokhberi Enon Eob Epbr123Euchiasmus Fathead99 Father Goose Fella22 Femto FernandoAC Fibula Flutefreek Fred Bauder Fredrik Fuhghettaboutit Fuzheado Gaff Gene Nygaard Georgiy1996 Gerry AshtonGiftlite Gilliam Glenn L GoingBatty Goobergunch Gregsexton Greyengine5 Grunt Gurch Gutza HLHJ Haemo Hammersbach Heracles31 Herbee Heron HikerBush Hqb IcairnsIgiffin Indefatigable Isis JBobbitt JHunterJ Jabowery JakeVortex Jamicanmonkey Jason Begin Jay Jc3s5h Jcronen1 Jdoherty Jeffz1 Jeronimo Jimmuhk Jimp Jimwilliams57 JoeinwapJohndburger Josh Parris Jq4bagiq Kaihsu KaneWang Keenan Pepper Kevin Rector KeyStorm Khukri Kurtan Lee Daniel Crocker LightYear Linuxoidoz Liv4christ210 Loggie Lolo252Lupinelawyer M ichaeligl MJCdetroit MTC Mac MacMcF Magore Markus Kuhn Masterqwe MaxHund Maxamegalon2000 Mbeychok Meggar Mh26 Michael Daly Michael Hardy MichelAudy Mikelifeguard Mikhailov Kusserow Mindbuilder Missvain Monger Mr bulow MrOllie MrZhuKeeper Muro de Aguas Mwanner Mwtoews Nandesuka Natkeeran Ndsg NgjaimeNhy67ygv Nick Y Nick123 NickPenguin Ninjagecko Noe Nosilleg Now3r3 Obelix homologator Oldadamml Oleg Alexandrov Olivier Ortolan88 OwenBlacker Pac72 PassargeaPatrick Paul Martin Peter Horn Physchim62 Piels Pierdm Pmanderson Prometheus235 Quadell QuantumEleven Quod erat demonstrandum 314159 Radagast83 Rccoms RedWolfReinyday Revipm Rexparry sydney Reyk Rhetth Rhialto Rich Farmbrough Richard Myers Rjwilmsi Rlsheehan Robin Barry RoySmith Rpwolfgram SD6-Agent SGBailey SamuelLowry Samw Sander123 Seabhcan SebastianHelm Sherbert1 Shinhan Shrew Sietse Snel SimonP Sinbaddasail0r Skotte Smalljim SomeHuman Spencer Srleffler StarwarsmastergeekSteacoon StefanK SteveRamone Stevertigo Stokerm Suisui Sunev Superboy112233 Superm401 Synchronism Tacoman1996 Tarquin Taw Teratornis The Man in Question ThierrycThingg Thinking of England Thunderbird2 Timwi Tobias Hoevekamp Tomasr Tonsofpcs Toon05 Topsykretts2512 Trekphiler Tuwile Twanvl Uday147502 Unitman00 UrhixidurUtherSRG Vargenau Vsmith WarrenPlatts Wasell Welsh Whispering Wikinger Wolfkeeper Wtmitchell XJamRastafire Xenonice Yath Zginder Zibem Zocky Zotel 713 anonymousedits
Name of unit Symbol Definition Relation to SIunits
angular mil micro equiv 2π6400 rad asymp 0981 748 times 10minus3
rad
arcminute equiv 1deg60 asymp 0290 888 times 10minus3
rad
arcsecond equiv 1deg3600 asymp 4848 137 times 10minus6
rad
centesimal minuteof arc
equiv 1 grad100 asymp 0157 080 times 10minus3
rad
centesimal secondof arc
equiv 1 grad(10 000) asymp 1570 796 times 10minus6
rad
degree (of arc) deg equiv 1360 of a revolution equiv π180 rad asymp 17453293 times 10minus3 rad
grad gradian gon grad equiv 1400 of a revolution equiv 2π400 rad equiv 09deg asymp 15707963 times 10minus3 rad
octant equiv 45deg asymp 0785 398 rad
quadrant equiv 90deg asymp 1570 796 rad
radian (SI unit) rad The angle subtended at the center of a circle by an arc whose length is equal to the circlesradius One full revolution encompasses 2π radians
= 1 rad
sextant equiv 60deg asymp 1047 198 rad
sign equiv 30deg asymp 0523 599 rad
Conversion of units 10
Solid angle
Solid angle
Name of unit Symbol Definition Relation to SIunits
steradian (SIunit)
sr The solid angle subtended at the center of a sphere of radius r by a portion of the surface of the spherehaving an area r2 A sphere encompasses 4π sr[14]
= 1 sr
MassNotesbull See Weight for detail of massweight distinction and conversionbull In this table the unit gee is used to denote standard gravity in order to avoid confusion with the g symbol for
gramsbull In physics the pound of mass is sometimes written lbm to distinguish it from the pound-force (lbf) It should not
be read as the mongrel unit pound metre
Mass
Name of unit Symbol Definition Relation to SI units
atomic mass unit unified u AMU asymp 1660 538 73 times 10minus27 plusmn 13 times 10minus36 kg
atomic unit of mass electron restmass
me asymp 9109 382 15 times 10minus31 plusmn 45 times 10minus39 kg[18]
bag (coffee) equiv 60 kg = 60 kg
bag (Portland cement) equiv 94 lb av = 42637 682 78 kg
barge equiv 22frac12 sh tn = 20 411656 65 kg
carat kt equiv 3 16 gr asymp 205196 548 333 mg
carat (metric) ct equiv 200 mg = 200 mg
clove equiv 8 lb av = 3628 738 96 kg
crith asymp 899349 mg
dalton Da asymp 1660 902 10 times 10minus27 plusmn 13 times 10minus36 kg
dram (apothecary troy) dr t equiv 60 gr = 3887 9346 g
dram (avoirdupois) dr av equiv 27 1132 gr = 1771 845 195 3125 g
electronvolt eV equiv 1 eV (energy unit) c2 = 17826 times 10minus36 kg
gamma γ equiv 1 μg = 1 μg
grain gr equiv 17000 lb av equiv 64798 91 mg
grave G grave was the original name of the kilogram equiv 1 kg
hundredweight (long) long cwt orcwt
equiv 112 lb av = 50802 345 44 kg
hundredweight (short) cental sh cwt equiv 100 lb av = 45359 237 kg
hyl (CGS unit) equiv 1 gee times 1 g times 1 s2m = 9806 65 g
hyl (MKS unit) equiv 1 gee times 1 kg times 1 s2m = 9806 65 kg
Conversion of units 11
kilogram kg equiv mass of the prototype near Paris (asymp mass of 1L ofwater)
equiv 1 kg (SI base unit)[8]
kip kip equiv 1000 lb av = 453592 37 kg
mark equiv 8 oz t = 248827 8144 g
mite equiv 120 gr = 3239 9455 mg
mite (metric) equiv 120 g = 50 mg
ounce (apothecary troy) oz t equiv 112 lb t = 31103 4768 g
ounce (avoirdupois) oz av equiv 116 lb = 28349 523 125 g
ounce (US food nutritionlabeling)
oz equiv 28 g[16] = 28 g
pennyweight dwt pwt equiv 120 oz t = 1555 173 84 g
point equiv 1100 ct = 2 mg
pound (avoirdupois) lb av equiv 0453 592 37 kg = 7000 grains equiv 0453 592 37 kg
pound (metric) equiv 500 g = 500 g
pound (troy) lb t equiv 5 760 grains = 0373 241 7216 kg
quarter (Imperial) equiv 14 long cwt = 2 st = 28 lb av = 12700 586 36 kg
quarter (informal) equiv frac14 short tn = 226796 185 kg
quarter long (informal) equiv frac14 long tn = 254011 7272 kg
quintal (metric) q equiv 100 kg = 100 kg
scruple (apothecary) s ap equiv 20 gr = 1295 9782 g
sheet equiv 1700 lb av = 6479891 mg
slug geepound slug equiv 1 gee times 1 lb av times 1 s2ft asymp 14593 903 kg
stone st equiv 14 lb av = 6350 293 18 kg
ton assay (long) AT equiv 1 mg times 1 long tn divide 1 oz t asymp 32666 667 g
ton assay (short) AT equiv 1 mg times 1 sh tn divide 1 oz t asymp 29166 667 g
ton long long tn or ton equiv 2 240 lb = 1 016046 9088 kg
ton short sh tn equiv 2 000 lb = 907184 74 kg
tonne (mts unit) t equiv 1 000 kg = 1 000 kg
wey equiv 252 lb = 18 st = 114305 277 24 kg (variants exist)
Zentner Ztr Definitions vary see [19] and[14]
Density
Conversion of units 12
Density
Name of unit Symbol Definition Relation to SI units
gram per millilitre gmL equiv gmL = 1000 kgm3
kilogram per cubic metre (SI unit) kgm3 equiv kgm3 = 1 kgm3
slug per cubic foot slugft3 equiv slugft3 asymp 5153788184 kgm3
Time
Time t
Name of unit Symbol Definition Relation to SI units
atomic unit of time au equiv a0(αmiddotc) asymp 2418 884 254 times 10minus17
s
Callippic cycle equiv 441 mo (hollow) + 499 mo (full) = 76 a of 36525 d = 2398 3776 times 109 s
century c equiv 100 a (see below for definition of year length) = 100 times year
day d = 24 h = 86400 s
day (sidereal) d equiv Time needed for the Earth to rotate once around its axisdetermined from successive transits of a very distantastronomical object across an observers meridian(International Celestial Reference Frame)
asymp 86 1641 s
decade dec equiv 10 a (see below for definition of year length) = 10 times year
fortnight fn equiv 2 wk = 1 209 600 s
helek equiv 11 080 h = 33 s
Hipparchic cycle equiv 4 Callippic cycles - 1 d = 9593 424 times 109 s
hour h equiv 60 min = 3 600 s
jiffy j equiv 160 s = 016 s
jiffy (alternate) ja equiv 1100 s = 10 ms
ke (quarter of an hour) equiv frac14 h = 196 d = 60 times 60 4 s = 900 s= 60 4 min = 15 min
Conversion of units 13
ke (traditional) equiv 1100 d = 24 times 60 times 60 100 s =864 s = 24 60 100min = 144 min
lustre lustrum equiv 5 a of 365 d = 15768 times 108 s
Metonic cycle enneadecaeteris equiv 110 mo (hollow) + 125 mo (full) = 6940 d asymp 19 a = 5996 16 times 108 s
millennium equiv 1 000 a (see below for definition of year length) = 1000 times year
milliday md equiv 11 000 d = 24 times 60 times 60 1 000 s= 864 s
minute min equiv 60 s due to leap seconds sometimes 59 s or 61 s = 60 s
moment equiv 90 s = 90 s
month (full) mo equiv 30 d[20] = 2 592 000 s
month (Greg av) mo Average Gregorian month = 365242512 d = 30436875 d asymp 26297 times 106 s
month (hollow) mo equiv 29 d[20] = 2 505 600 s
month (synodic) mo Cycle time of moon phases asymp 29530589 days (Average) asymp 2551 times 106 s
octaeteris = 48 mo (full) + 48 mo (hollow) + 3 mo (full)[21] [22] = 8 aof 36525 d = 2922 d
= 2524 608 times 108 s
Planck time equiv (Gℏc5)frac12 asymp 1351 211 868 times 10minus43
s
second s time of 9 192 631 770 periods of the radiation correspondingto the transition between the 2 hyperfine levels of the groundstate of the caesium 133 atom at 0 K[8] (but other secondsare sometimes used in astronomy)
(SI base unit)
shake equiv 10minus8 s = 10 ns
sigma equiv 10minus6 s = 1 μs
Sothic cycle equiv 1 461 a of 365 d = 4607 4096 times 1010 s
svedberg S equiv 10minus13 s = 100 fs
week wk equiv 7 d = 604 800 s
year (Gregorian) a y oryr
= 3652425 d average calculated from common years (365d) plus leap years (366 d) on most years divisible by 4 Seeleap year for details
= 31 556 952 s
year (Julian) a y oryr
= 36525 d average calculated from common years (365 d)plus one leap year (366 d) every four years
= 31 557 600 s
year (sidereal) a y oryr
equiv time taken for Sun to return to the same position withrespect to the stars of the celestial sphere
asymp 365256 363 d asymp 31558 1497632 s
year (tropical) a y oryr
equiv Length of time it takes for the Sun to return to the sameposition in the cycle of seasons
asymp 365242 190 d asymp 31556 925 s
Where UTC is observed the length of timeunits longer than 1 s may increase or decreaseby 1 s if a leap second occurs during the timeinterval of interest
Conversion of units 14
Frequency
Frequency
Name of unit Symbol Definition Relation to SI units
hertz (SI unit) Hz equiv Number of cycles per second = 1 Hz = 1s
revolutions per minute rpm equiv One unit rpm equals one rotation completed around a fixed axis in one minute of time asymp0104719755 rads
Speed or velocity
Speed
Name of unit Symbol Definition Relation to SI units
foot per hour fph equiv 1 fth asymp 8466 667 times 10minus5
ms
foot per minute fpm equiv 1 ftmin = 508 times 10minus3 ms
foot per second fps equiv 1 fts = 3048 times 10minus1 ms
furlong perfortnight
equiv furlongfortnight asymp 1663 095 times 10minus4
ms
inch per minute ipm equiv 1 inmin asymp 423 333 times 10minus4 ms
inch per second ips equiv 1 ins = 254 times 10minus2 ms
mach number M Ratio of the speed to the speed of sound in the medium Varies especially with temperatureAbout 761 mph (1225 kph) in air at sea level to about 660 mph (1062 kph) at jet altitudesUnitless
asymp 340 to 295 ms foraircraft
metre per second(SI unit)
ms equiv 1 ms = 1 ms
mile per hour mph equiv 1 mih = 0447 04 ms
mile per minute mpm equiv 1 mimin = 268224 ms
mile per second mps equiv 1 mis = 1 609344 ms
speed of light invacuum
c equiv 299 792 458 ms = 299 792 458 ms
speed of sound inair
s Varies especially with temperature About 761 mph (1225 kph) in air at sea level to about660 mph (1062 kph) at jet altitudes
asymp 340 to 295 ms ataircraft altitudes
A velocity consists of a speed combined with a direction the speed part of the velocity takes units of speed
Conversion of units 15
Flow (volume)
Flow
Name of unit Symbol Definition Relation to SI units
cubic foot per minute CFM equiv 1 ft3min = 4719474432 times 10minus4 m3s
cubic foot per second ft3s equiv 1 ft3s = 0028316846592 m3s
cubic inch per minute in3min equiv 1 in3min = 27311773 times 10minus7 m3s
cubic inch per second in3s equiv 1 in3s = 16387064 times 10minus5 m3s
cubic metre per second (SIunit)
m3s equiv 1 m3s = 1 m3s
gallon (US fluid) per day GPD equiv 1 gald = 4381263638 times 10minus8 m3s
gallon (US fluid) per hour GPH equiv 1 galh = 1051503273 times 10minus6 m3s
gallon (US fluid) per minute GPM equiv 1 galmin = 630901964 times 10minus5 m3s
litre per minute LPM equiv 1 Lmin = 16 times 10minus5 m3s
Acceleration
Acceleration
Name of unit Symbol Definition Relation to SI units
foot per hour per second fphs equiv 1 ft(hmiddots) asymp 8466 667 times 10minus5
ms2
foot per minute per second fpms equiv 1 ft(minmiddots) = 508 times 10minus3 ms2
foot per second squared fps2 equiv 1 fts2 = 3048 times 10minus1 ms2
gal galileo Gal equiv 1 cms2 = 10minus2 ms2
inch per minute per second ipms equiv 1 in(minmiddots) asymp 4233 333 times 10minus4
ms2
inch per second squared ips2 equiv 1 ins2 = 254 times 10minus2 ms2
knot per second kns equiv 1 kns asymp 5144 444 times 10minus1
ms2
metre per second squared (SI unit) ms2 equiv 1 ms2 = 1 ms2
mile per hour per second mphs equiv 1 mi(hmiddots) = 44704 times 10minus1 ms2
mile per minute per second mpms equiv 1 mi(minmiddots) = 268224 ms2
mile per second squared mps2 equiv 1 mis2 = 1609 344 times 103 ms2
standard gravity g equiv 9806 65 ms2 = 9806 65 ms2
Conversion of units 16
Force
Force
Name of unit Symbol Definition Relation to SI units
atomic unit of force equiv memiddotα2middotc2a0 asymp 8238 722 06 times 10minus8 N
[23]
dyne (cgs unit) dyn equiv gmiddotcms2 = 10minus5 N
kilogram-force kilopondgrave-force
kgf kp Gf equiv g times 1 kg = 9806 65 N
kip kip-force kip kipfklbf
equiv g times 1 000 lb = 4448 221 6152605 times 103 N
milligrave-force gravet-force mGf gf equiv g times 1 g = 9806 65 mN
newton (SI unit) N A force capable of giving a mass of one kg an acceleration of one metreper second per second[24]
= 1 N = 1 kgmiddotms2
ounce-force ozf equiv g times 1 oz = 0278 013 850 9537812 N
pound lb equiv slugmiddotfts2 = 4448 230 531 N
pound-force lbf equiv g times 1 lb = 4448 221 615 2605 N
poise (cgs unit) P equiv 10minus1 Pamiddots = 01 Pamiddots
pound per foot hour lb(ftmiddoth) equiv 1 lb(ftmiddoth) asymp 4133 789 times 10minus4 Pamiddots
pound per foot second lb(ftmiddots) equiv 1 lb(ftmiddots) asymp 1488164 Pamiddots
pound-force second per square foot lbfmiddotsft2 equiv 1 lbfmiddotsft2 asymp 4788026 Pamiddots
pound-force second per square inch lbfmiddotsin2 equiv 1 lbfmiddotsin2 asymp 6894757 Pamiddots
Conversion of units 21
Kinematic viscosity
Kinematic viscosity
Name of unit Symbol Definition Relation to SI units
square foot per second ft2s equiv 1 ft2s = 009290304 m2s
square metre per second (SI unit) m2s equiv 1 m2s = 1 m2s
stokes (cgs unit) St equiv10minus4 m2s
= 10minus4 m2s
Electric current
Electric current
Name of unit Symbol Definition Relation to SI units
ampere (SI base unit) A equiv The constant current needed to produce a force of 2 times 10minus7 newton per metre betweentwo straight parallel conductors of infinite length and negligible circular cross-sectionplaced one metre apart in a vacuum[8]
= 1 A
electromagnetic unitabampere (cgs unit)
abamp equiv 10 A = 10 A
esu per secondstatampere (cgs unit)
esus equiv (01 Amiddotms) c asymp3335641 times 10minus10 A
Electric charge
Electric charge
Name of unit Symbol Definition Relation to SI units
abcoulomb electromagnetic unit (cgsunit)
abC emu equiv 10 C = 10 C
atomic unit of charge au equiv e asymp 1602 176462 times 10minus19 C
coulomb (SI unit) C equiv The amount of electricity carried in one second of time by oneampere of current[24]
= 1 C = 1 Amiddots
faraday F equiv 1 mol times NAmiddote asymp 96 4853383 C
statcoulomb franklin electrostatic unit(cgs unit)
statC Fresu
equiv (01 Amiddotm) c asymp 3335 641 times 10minus10 C
Conversion of units 22
Electric dipole
Electric dipole
Name of unit Symbol Definition Relation to SI units
atomic unit of electric dipole moment ea0 asymp 8478 352 81 times 10minus30
Cmiddotm[28]
Electromotive force electric potential difference
Voltage electromotive force
Name ofunit
Symbol Definition Relation to SI units
abvolt (cgsunit)
abV equiv 1 times 10minus8 V = 1 times 10minus8 V
statvolt (cgsunit)
statV equiv cmiddot (1 μJAmiddotm) = 299792 458 V
volt (SIunit)
V The difference in electric potential across two points along a conducting wire carrying one ampereof constant current when the power dissipated between the points equals one watt[24]
= 1 V = 1 WA = 1kgmiddotm2(Amiddots3)
Electrical resistance
Electrical resistance
Name ofunit
Symbol Definition Relation to SI units
ohm (SIunit)
Ω The resistance between two points in a conductor when one volt of electric potential differenceapplied to these points produces one ampere of current in the conductor[24]
= 1 Ω = 1 VA = 1kgmiddotm2(A2middots3)
Capacitance
Capacitors ability to store charge
Name ofunit
Symbol Definition Relation to SI units
farad (SIunit)
F The capacitance between two parallel plates that results in one volt of potential difference whencharged by one coulomb of electricity[24]
= 1 F = 1 CV = 1A2middots4(kgmiddotm2)
Conversion of units 23
Magnetic flux
magnetic flux
Name of unit Symbol Definition Relation to SI units
maxwell (CGSunit)
Mx equiv 10minus8 Wb[29] = 1 times 10minus8 Wb
weber (SIunit)
Wb Magnetic flux which linking a circuit of one turn would produce in it an electromotive force of1 volt if it were reduced to zero at a uniform rate in 1 second[24]
= 1 Wb = 1 Vmiddots = 1kgmiddotm2(Amiddots2)
Magnetic flux density
What physicists call Magnetic field is called Magnetic flux density by electrical engineersand magnetic induction by applied mathematicians and electrical engineers
Name of unit Symbol Definition Relation to SI units
gauss (CGS unit) G equiv Mxcm2 = 10minus4
T= 1 times 10minus4 T [30]
tesla (SI unit) T equiv Wbm2 = 1 T = 1 Wbm2 = 1kg(Amiddots2)
Inductance
Inductance
Name ofunit
Symbol Definition Relation to SI units
henry (SIunit)
H The inductance of a closed circuit that produces one volt of electromotive force when the current inthe circuit varies at a uniform rate of one ampere per second[24]
= 1 H = 1 WbA = 1kgmiddotm2(Amiddots)2
Temperature
Temperature
Name of unit Symbol Definition Conversion to kelvin
degree Celsius degC degC equiv K minus 27315 [K] equiv [degC] + 27315
degree Delisle degDe [K] = 37315 minus [degDe] times 23
degree Fahrenheit degF degF equiv degC times 95 + 32 [K] equiv ([degF] + 45967) times 59
degree Newton degN [K] = [degN] times 10033 + 27315
degree Rankine degR degRa degR equiv K times 95 [K] equiv [degR] times 59
degree Reacuteaumur degReacute [K] = [degReacute] times 54 + 27315
degree Roslashmer degRoslash [K] = ([degRoslash] minus 75) times 4021 + 27315
kelvin (SI baseunit)
K equiv 127316 of the thermodynamic temperature of the triple point of water[8] equiv 1 K
Conversion of units 24
Information entropy
Information entropy
Name of unit Symbol Definition Relation to SI units Relation to bits
SI unit JK equiv JK = 1 JK
nat nip nepit nat equiv kB = 1380 650 5(23) times 10minus23 JK
bit shannon bit b Sh equiv ln(2) times kB = 9569 940 (16) times 10minus24 JK = 1 bit
ban hartley ban Hart equiv ln(10) times kB = 3179 065 3(53) times 10minus23 JK
nibble equiv 4 bits = 3827 976 0(64) times 10minus23 JK = 22 bit
byte B equiv 8 bits = 7655 952 (13) times 10minus23 JK = 23 bit
kilobyte (decimal) kB equiv 1 000 B = 7655 952 (13) times 10minus20 JK
kilobyte (kibibyte) KB KiB equiv 1 024 B = 7839 695 (13) times 10minus20 JK = 210 bit
Often information entropy is measured in shannons whereas the (discrete) storage space of digital devices ismeasured in bits Thus uncompressed redundant data occupy more than one bit of storage per shannon ofinformation entropy The multiples of a bit listed above are usually used with this meaning Other times the bit isused as a measure of information entropy and is thus a synonym of shannon
Luminous intensityThe candela is the preferred nomenclature for the SI unit
Luminous intensity
Name of unit Symbol Definition Relation toSI units
candela (SI baseunit) candle
cd The luminous intensity in a given direction of a source that emits monochromatic radiation offrequency 540 times 1012 hertz and that has a radiant intensity in that direction of 1683 watt persteradian[8]
= 1 cd
candlepower (new) cp equiv cd The use of candlepower as a unit is discouraged due to its ambiguity = 1 cd
candlepower (oldpre-1948)
cp Varies and is poorly reproducible[31] Approximately 0981 cd[14] asymp 0981 cd
Luminance
Conversion of units 25
Luminance
Name of unit Symbol Definition Relation to SI units
candela per square foot cdft2 equiv cdft2 asymp10763910417 cdm2
candela per square inch cdin2 equiv cdin2 asymp 15500031 cdm2
candela per square metre (SI unit) nit (deprecated[14] ) cdm2 equiv cdm2 = 1 cdm2
Name of unit Symbol Definition Relation to SI units
lumen (SIunit)
lm equiv cdmiddotsr = 1 lm = 1 cdmiddotsr
Illuminance
Illuminance
Name of unit Symbol Definition Relation to SI units
footcandle lumen per square foot fc equiv lmft2 = 10763910417 lx
lumen per square inch lmin2 equiv lmin2 asymp 15500031 lx
lux (SI unit) lx equiv lmm2 = 1 lx = 1 lmm2
phot (CGS unit) ph equiv lmcm2 = 1 times 104 lx
Radiation - source activity
Conversion of units 26
Radioactivity
Name of unit Symbol Definition Relation to SI units
becquerel (SIunit)
Bq equiv Number of disintegrations per second = 1 Bq = 1s
curie Ci equiv 37 times 1010 Bq = 37 times 1010 Bq [32]
rutherford (H) rd equiv 1 MBq = 1 times 106 Bq
Please note that although becquerel (Bq) and hertz (Hz) both ultimately refer to the same SI base unit (sminus1) Hz isused only for periodic phenomena and Bq is only used for stochastic processes associated with radioactivity[33]
Radiation - exposure
Radiation - exposure
Name of unit Symbol Definition Relation to SI units
roentgen R 1 R equiv 258 times 10minus4 Ckg[29] = 258 times 10minus4 Ckg
The roentgen is not a SI unit and the NIST strongly discourages its continued use[34]
Radiation - absorbed dose
Radiation - absorbed dose
Name of unit Symbol Definition Relation to SI units
Name of unit Symbol Definition Relation to SI units
Roumlntgen equivalent man rem equiv 001 Sv = 001 Sv
sievert (SI unit) Sv equiv 1 Jkg[33] = 1 Sv
Although the definitions for sievert (Sv) and gray (Gy) would seem to indicate that they measure the same quantitiesthis is not the case The effect of receiving a certain dose of radiation (given as Gy) is variable and depends on manyfactors thus a new unit was needed to denote the biological effectiveness of that dose on the body this is known asthe equivalent dose and is shown in Sv The general relationship between absorbed dose and equivalent dose can berepresented as
H = Q middot D
where H is the equivalent dose D is the absorbed dose and Q is a dimensionless quality factor Thus for anyquantity of D measured in Gy the numerical value for H measured in Sv may be different[36]
Conversion of units 27
Software toolsHome and office computers come with converters in bundled spreadsheet applications or can access free convertersvia the Internet Units and measurements can be easily converted using these tools but only if the units are explicitlydefined and the conversion is compatible (eg cmHg to kPa)
Free conversion softwarebull Units (software) a popular cross-platform command-line utilitybull Converter [37] contextual unit converter for Mozilla Firefox browsersbull Converber [38] portable application converting utilitybull calculla [39] calculla - online web convertersbull iMetrix [40] - unit converter for xpbull uniteasy [41] online scientific unit conversionbull Unit Converter Add-in for Excel [42] - allow a large selection of unit conversions within the Microsoft Excel
spread sheet programbull Unit Converter [43] simple and extensible unit converterbull Portable Unit Converter [44] including 4500 units 33 unit-categories and the possibility to create custom units
General commercial sources of convertersbull Advanced electronic calculators have unit-conversion functionalitybull Spreadsheet programs usually provide conversion functions or formulas or the user can write their ownbull Commercial mathematical scientific and technical applications often include converters
See also
bull Accuracy and precisionbull English unitsbull False precisionbull Imperial unitsbull International System of Unitsbull Mesures usuellesbull Metric system
bull Natural unitsbull Roundingbull Significant figuresbull Temperature conversionbull United States customary unitsbull Units conversion by factor-labelbull Units of measurement
External linksbull British law Units of measurement regulations 1995 [45]
bull ConvertBuster [46] Variety of conversion tools to convert easilybull How Many A dictionary of units of measurement [47]
bull NIST Fundamental physical constants mdash Non-SI units [48]PDF (357 KB)bull NIST Guide to SI Units [49] Many conversion factors listedbull Online Conversion Calculators [50] Very extensive list of conversions from-to equvalent unitsbull The Unified Code for Units of Measure [51]
bull Units Symbols and Conversions XML Dictionary [52]
bull Multilingual Online Conversion of Units [53]
bull Temperature Converter [54]
Conversion of units 28
References[1] United States Naval Observatory (2009) Selected Astronomical Constants 2009 (http asa usno navy mil SecK 2009
Astronomical_Constants_2009 txt) Accessed May 10 2009[2] NIST Reference on Constants Units and Uncertainty (http physics nist gov cgi-bin cuu Valuebohrrada0|search_for=Bohr+
radius)(2006) National Institute of Standards and Technology Retrieved February 22 2008[3] National Institute of Standards and Technology General Tables of Units of Measurement (http ts nist gov WeightsAndMeasures
Publications appxc cfm)[4] Lide D (Ed) (1990) Handbook of Chemistry and Physics (71st ed) Boca Raton FL CRC Press Section 1[5] National Bureau of Standards (June 30 1959) Refinement of values for the yard and the pound Federal Register viewed September 20
2006 at National Geodetic Survey web site (http www ngs noaa gov PUBS_LIB FedRegister FRdoc59-5442 pdf)[6] The International Astronomical Union and Astronomical Units (http www iau org public_press themes measuring )[7] Klein Herbert Arthur (1988) The Science of Measurement a Historical Survey Mineola NY Dover Publications 0-4862-5839-4[8] The International System of Units Section 21 (http www bipm org en si si_brochure chapter2 2-1 ) (8 ed) Bureau International des
Poids et Mesures 2006 retrieved August 26 2009[9] International System of Units (http www bipm org en si si_brochure chapter4 table8 html) 8th ed (2006) Bureau International des
Poids et Mesures Section 41 Table 8[10] P Kenneth Seidelmann Ed (1992) Explanatory Supplement to the Astronomical Almanac Sausalito CA University Science Books p 716
and sv parsec in Glossary[11] Whitelaw Ian (2007) A Measure of All Things The Story of Man and Measurement (http books google com
booksid=3zgGEWM5-iAC) New York Macmillan 0-312-37026-1 p 152[12] De Vinne Theodore Low (1900) The practice of typography a treatise on the processes of type-making the point system the names sizes
styles and prices of plain printing types (http books google com booksid=R4-DjphIpLMC) 2nd ed New York The Century Co p142ndash150
[13] Pasko Wesley Washington (1894) American dictionary of printing and bookmaking (http books google combooksid=Z_QUAAAAIAAJ) (1894) New York Howard Lockwood p 521
[14] Rowlett Russ (2005) How Many A Dictionary of Units of Measurement (http www unc edu ~rowlett units index html)[15] Thompson A and Taylor BN (2008) Guide for the Use of the International System of Units (SI) National Institute of Standards and
Technology Special Publication 811 p 57[16] US Code of Federal Regulations Title 21 Section 1019 Paragraph (b)(5)(viii) (http ecfr gpoaccess gov cgi t text text-idxc=ecframp
rgn=div8amp view=textamp node=212 0 1 1 2 1 1 6amp idno=21) retrieved August 29 2009[17] Barry N Taylor Ed NIST Special Publication 330 The International System of Units (SI) (http physics nist gov Pubs SP330 sp330
pdf) (2001 Edition) Washington US Government Printing Office 43The 12th Conference Generale des Poids et Mesures(CGPM)hellipdeclares that the word ldquolitrerdquo may be employed as a special name for the cubic decimetre
[18] CODATA Value atomic uint of mass (http physics nist gov cgi-bin cuu Valuettme|search_for=atomic+ unit+ of+ mass) (2006)National Institute of Standards and Technology Retrieved 16 September 2008
[19] The Swiss Federal Office for Metrology gives Zentner on a German language web page (http www metas ch de scales systemch html)and quintal on the English translation of that page (http www metas ch en scales systemch html) the unit is marked speacutecifiquementsuisse
[20] Pedersen O (1983) Glossary in Coyne G Hoskin M and Pedersen O Gregorian Reform of the Calendar Proceedings of the VaticanConference to Commemorate its 400th Anniversary Vatican Observatory Available from Astrophysics Data System
[21] Richards EG (1998) Mapping Time Oxford University Press pp 94ndash95 ISBN 0-19-850413-6[22] Steel Duncan (2000) Marking Time John Wiley amp Sons p 46 ISBN 0-471-29827-1[23] CODATA Value atomic unit of force (http physics nist gov cuu Constants ) (2006) National Institute of Standards and Technology
Retrieved September 14 2008[24] [[Comiteacute International des Poids et Mesures (http www bipm org en CIPM db 1946 2 )] Resolution 2] 1946 retrieved August 26
2009[25] Barry N Taylor (April 1995) Guide for the Use of the International System of Units (SI) (http physics nist gov cuu pdf sp811 pdf)
(NIST Special Publication 811) Washington DC US Government Printing Office pp 57ndash68[26] Barry N Taylor (April 1995) Guide for the Use of the International System of Units (SI) (NIST Special Publication 811) Washington DC
US Government Printing Office p 5[27] International System of Units (http www bipm org en si si_brochure chapter4 table7 html) 8th ed (2006) Bureau International des
Poids et Mesures Section 41 Table 7[28] The NIST Reference on Constants Units and Uncertainty (http physics nist gov cgi-bin cuu Valueauedm) 2006 retrieved August
26 2009[29] NIST Guide to SI Units Appendix B9 (http physics nist gov Pubs SP811 appenB9 html) retrieved August 27 2009[30] Standard for the Use of the International System of Units (SI) The Modern Metric System IEEEASTM SI 10-1997 (1997) New York and
West Conshohocken PA Institute of Electrical and Electronics Engineers and American Society for Testing and Materials Tables A1through A5
Conversion of units 29
[31] The NIST Reference on Constants Units and Uncertainty (http physics nist gov cuu Units candela html) retrieved August 28 2009[32] Ambler Thompson amp Barry N Taylor (2008) Guide for the Use of the International System of Units (SI) (http physics nist gov cuu
pdf sp811 pdf) Special Publication 811 Gaithersburg MD National Institute of Standards and Technology p 10[33] The International System of Units Section 222 Table 3 (http www bipm org en si si_brochure chapter2 2-2 table3 html) (8 ed)
Bureau International des Poids et Mesures 2006 retrieved August 27 2009[34] The NIST Guide to the SI (Special Publication 811) section 52 (http physics nist gov Pubs SP811 sec05 html5 2) 2008 retrieved
August 27 2009[35] Ambler Thompson amp Barry N Taylor (2008) Guide for the Use of the International System of Units (SI) (http physics nist gov cuu
pdf sp811 pdf) Special Publication 811 Gaithersburg MD National Institute of Standards and Technology p 5[36] [[Comiteacute international des poids et mesures (http www bipm org en CIPM db 2002 2 )] 2002 Recommendation 2] retrieved
August 27 2009[37] http converter mozdev org[38] http www xyntec com converber htm[39] http www calculla com[40] http illusions hu index phptask=100amp lang=0amp statpage=86[41] http www uniteasy com[42] http www tenderwire com wikipedialandingpage[43] http www kamlex com index phpoption=com_contentamp view=articleamp id=53amp Itemid=55[44] http www sttmedia com unitconverter[45] http www hmso gov uk si si1995 Uksi_19951804_en_2 htm[46] http www convertbuster com[47] http www unc edu ~rowlett units[48] http physics nist gov cuu Document nonsi_in_1998 pdf[49] http physics nist gov Pubs SP811 appenB9 html[50] http www onlineconversion com[51] http aurora rg iupui edu ~schadow units UCUM ucum html[52] http www posc org refs poscUnits20 xml[53] http www imperialtometric com[54] http www tampile com
Article Sources and Contributors 30
Article Sources and ContributorsConversion of units Source httpenwikipediaorgwindexphpoldid=373975089 Contributors 1571781xxx 7 A-giau AVSI Acather96 Ahoerstemeier Alexius08 Altenmann AndreEngels Andrewa Andy120290 Anonymi Ariconte Army1987 ArnoldReinhold Arthur3030 Aspects AxelBoldt AzaToth Azikala BW95 Bdesham Beland Bensaccount Bkumartvm Blackand White BlaiseFEgan BlueEarth Bobblewik Borbrav Bpmullins Bryan Derksen C J B Scholten CORNELIUSSEON CTZMSC3 Calltech Camerajohn Chaosfeary Charles MatthewsChris the speller Cmdrjameson Colonies Chris Conversion script Cope555 Crappy13 Crissov CyrilB DARTH SIDIOUS 2 DMacks DanielCD Dark Formal DarkestSideX DekisugiDenelson83 Dhp1080 Dicklyon DirkvdM Donald Duck Donarreiskoffer Dramatic Dyss DAringsbquougosz Egil Ehrenkater Ejohnsonboulder Elexmax Elf Emokhberi Enon Eob Epbr123Euchiasmus Fathead99 Father Goose Fella22 Femto FernandoAC Fibula Flutefreek Fred Bauder Fredrik Fuhghettaboutit Fuzheado Gaff Gene Nygaard Georgiy1996 Gerry AshtonGiftlite Gilliam Glenn L GoingBatty Goobergunch Gregsexton Greyengine5 Grunt Gurch Gutza HLHJ Haemo Hammersbach Heracles31 Herbee Heron HikerBush Hqb IcairnsIgiffin Indefatigable Isis JBobbitt JHunterJ Jabowery JakeVortex Jamicanmonkey Jason Begin Jay Jc3s5h Jcronen1 Jdoherty Jeffz1 Jeronimo Jimmuhk Jimp Jimwilliams57 JoeinwapJohndburger Josh Parris Jq4bagiq Kaihsu KaneWang Keenan Pepper Kevin Rector KeyStorm Khukri Kurtan Lee Daniel Crocker LightYear Linuxoidoz Liv4christ210 Loggie Lolo252Lupinelawyer M ichaeligl MJCdetroit MTC Mac MacMcF Magore Markus Kuhn Masterqwe MaxHund Maxamegalon2000 Mbeychok Meggar Mh26 Michael Daly Michael Hardy MichelAudy Mikelifeguard Mikhailov Kusserow Mindbuilder Missvain Monger Mr bulow MrOllie MrZhuKeeper Muro de Aguas Mwanner Mwtoews Nandesuka Natkeeran Ndsg NgjaimeNhy67ygv Nick Y Nick123 NickPenguin Ninjagecko Noe Nosilleg Now3r3 Obelix homologator Oldadamml Oleg Alexandrov Olivier Ortolan88 OwenBlacker Pac72 PassargeaPatrick Paul Martin Peter Horn Physchim62 Piels Pierdm Pmanderson Prometheus235 Quadell QuantumEleven Quod erat demonstrandum 314159 Radagast83 Rccoms RedWolfReinyday Revipm Rexparry sydney Reyk Rhetth Rhialto Rich Farmbrough Richard Myers Rjwilmsi Rlsheehan Robin Barry RoySmith Rpwolfgram SD6-Agent SGBailey SamuelLowry Samw Sander123 Seabhcan SebastianHelm Sherbert1 Shinhan Shrew Sietse Snel SimonP Sinbaddasail0r Skotte Smalljim SomeHuman Spencer Srleffler StarwarsmastergeekSteacoon StefanK SteveRamone Stevertigo Stokerm Suisui Sunev Superboy112233 Superm401 Synchronism Tacoman1996 Tarquin Taw Teratornis The Man in Question ThierrycThingg Thinking of England Thunderbird2 Timwi Tobias Hoevekamp Tomasr Tonsofpcs Toon05 Topsykretts2512 Trekphiler Tuwile Twanvl Uday147502 Unitman00 UrhixidurUtherSRG Vargenau Vsmith WarrenPlatts Wasell Welsh Whispering Wikinger Wolfkeeper Wtmitchell XJamRastafire Xenonice Yath Zginder Zibem Zocky Zotel 713 anonymousedits
Name of unit Symbol Definition Relation to SIunits
angular mil micro equiv 2π6400 rad asymp 0981 748 times 10minus3
rad
arcminute equiv 1deg60 asymp 0290 888 times 10minus3
rad
arcsecond equiv 1deg3600 asymp 4848 137 times 10minus6
rad
centesimal minuteof arc
equiv 1 grad100 asymp 0157 080 times 10minus3
rad
centesimal secondof arc
equiv 1 grad(10 000) asymp 1570 796 times 10minus6
rad
degree (of arc) deg equiv 1360 of a revolution equiv π180 rad asymp 17453293 times 10minus3 rad
grad gradian gon grad equiv 1400 of a revolution equiv 2π400 rad equiv 09deg asymp 15707963 times 10minus3 rad
octant equiv 45deg asymp 0785 398 rad
quadrant equiv 90deg asymp 1570 796 rad
radian (SI unit) rad The angle subtended at the center of a circle by an arc whose length is equal to the circlesradius One full revolution encompasses 2π radians
= 1 rad
sextant equiv 60deg asymp 1047 198 rad
sign equiv 30deg asymp 0523 599 rad
Conversion of units 10
Solid angle
Solid angle
Name of unit Symbol Definition Relation to SIunits
steradian (SIunit)
sr The solid angle subtended at the center of a sphere of radius r by a portion of the surface of the spherehaving an area r2 A sphere encompasses 4π sr[14]
= 1 sr
MassNotesbull See Weight for detail of massweight distinction and conversionbull In this table the unit gee is used to denote standard gravity in order to avoid confusion with the g symbol for
gramsbull In physics the pound of mass is sometimes written lbm to distinguish it from the pound-force (lbf) It should not
be read as the mongrel unit pound metre
Mass
Name of unit Symbol Definition Relation to SI units
atomic mass unit unified u AMU asymp 1660 538 73 times 10minus27 plusmn 13 times 10minus36 kg
atomic unit of mass electron restmass
me asymp 9109 382 15 times 10minus31 plusmn 45 times 10minus39 kg[18]
bag (coffee) equiv 60 kg = 60 kg
bag (Portland cement) equiv 94 lb av = 42637 682 78 kg
barge equiv 22frac12 sh tn = 20 411656 65 kg
carat kt equiv 3 16 gr asymp 205196 548 333 mg
carat (metric) ct equiv 200 mg = 200 mg
clove equiv 8 lb av = 3628 738 96 kg
crith asymp 899349 mg
dalton Da asymp 1660 902 10 times 10minus27 plusmn 13 times 10minus36 kg
dram (apothecary troy) dr t equiv 60 gr = 3887 9346 g
dram (avoirdupois) dr av equiv 27 1132 gr = 1771 845 195 3125 g
electronvolt eV equiv 1 eV (energy unit) c2 = 17826 times 10minus36 kg
gamma γ equiv 1 μg = 1 μg
grain gr equiv 17000 lb av equiv 64798 91 mg
grave G grave was the original name of the kilogram equiv 1 kg
hundredweight (long) long cwt orcwt
equiv 112 lb av = 50802 345 44 kg
hundredweight (short) cental sh cwt equiv 100 lb av = 45359 237 kg
hyl (CGS unit) equiv 1 gee times 1 g times 1 s2m = 9806 65 g
hyl (MKS unit) equiv 1 gee times 1 kg times 1 s2m = 9806 65 kg
Conversion of units 11
kilogram kg equiv mass of the prototype near Paris (asymp mass of 1L ofwater)
equiv 1 kg (SI base unit)[8]
kip kip equiv 1000 lb av = 453592 37 kg
mark equiv 8 oz t = 248827 8144 g
mite equiv 120 gr = 3239 9455 mg
mite (metric) equiv 120 g = 50 mg
ounce (apothecary troy) oz t equiv 112 lb t = 31103 4768 g
ounce (avoirdupois) oz av equiv 116 lb = 28349 523 125 g
ounce (US food nutritionlabeling)
oz equiv 28 g[16] = 28 g
pennyweight dwt pwt equiv 120 oz t = 1555 173 84 g
point equiv 1100 ct = 2 mg
pound (avoirdupois) lb av equiv 0453 592 37 kg = 7000 grains equiv 0453 592 37 kg
pound (metric) equiv 500 g = 500 g
pound (troy) lb t equiv 5 760 grains = 0373 241 7216 kg
quarter (Imperial) equiv 14 long cwt = 2 st = 28 lb av = 12700 586 36 kg
quarter (informal) equiv frac14 short tn = 226796 185 kg
quarter long (informal) equiv frac14 long tn = 254011 7272 kg
quintal (metric) q equiv 100 kg = 100 kg
scruple (apothecary) s ap equiv 20 gr = 1295 9782 g
sheet equiv 1700 lb av = 6479891 mg
slug geepound slug equiv 1 gee times 1 lb av times 1 s2ft asymp 14593 903 kg
stone st equiv 14 lb av = 6350 293 18 kg
ton assay (long) AT equiv 1 mg times 1 long tn divide 1 oz t asymp 32666 667 g
ton assay (short) AT equiv 1 mg times 1 sh tn divide 1 oz t asymp 29166 667 g
ton long long tn or ton equiv 2 240 lb = 1 016046 9088 kg
ton short sh tn equiv 2 000 lb = 907184 74 kg
tonne (mts unit) t equiv 1 000 kg = 1 000 kg
wey equiv 252 lb = 18 st = 114305 277 24 kg (variants exist)
Zentner Ztr Definitions vary see [19] and[14]
Density
Conversion of units 12
Density
Name of unit Symbol Definition Relation to SI units
gram per millilitre gmL equiv gmL = 1000 kgm3
kilogram per cubic metre (SI unit) kgm3 equiv kgm3 = 1 kgm3
slug per cubic foot slugft3 equiv slugft3 asymp 5153788184 kgm3
Time
Time t
Name of unit Symbol Definition Relation to SI units
atomic unit of time au equiv a0(αmiddotc) asymp 2418 884 254 times 10minus17
s
Callippic cycle equiv 441 mo (hollow) + 499 mo (full) = 76 a of 36525 d = 2398 3776 times 109 s
century c equiv 100 a (see below for definition of year length) = 100 times year
day d = 24 h = 86400 s
day (sidereal) d equiv Time needed for the Earth to rotate once around its axisdetermined from successive transits of a very distantastronomical object across an observers meridian(International Celestial Reference Frame)
asymp 86 1641 s
decade dec equiv 10 a (see below for definition of year length) = 10 times year
fortnight fn equiv 2 wk = 1 209 600 s
helek equiv 11 080 h = 33 s
Hipparchic cycle equiv 4 Callippic cycles - 1 d = 9593 424 times 109 s
hour h equiv 60 min = 3 600 s
jiffy j equiv 160 s = 016 s
jiffy (alternate) ja equiv 1100 s = 10 ms
ke (quarter of an hour) equiv frac14 h = 196 d = 60 times 60 4 s = 900 s= 60 4 min = 15 min
Conversion of units 13
ke (traditional) equiv 1100 d = 24 times 60 times 60 100 s =864 s = 24 60 100min = 144 min
lustre lustrum equiv 5 a of 365 d = 15768 times 108 s
Metonic cycle enneadecaeteris equiv 110 mo (hollow) + 125 mo (full) = 6940 d asymp 19 a = 5996 16 times 108 s
millennium equiv 1 000 a (see below for definition of year length) = 1000 times year
milliday md equiv 11 000 d = 24 times 60 times 60 1 000 s= 864 s
minute min equiv 60 s due to leap seconds sometimes 59 s or 61 s = 60 s
moment equiv 90 s = 90 s
month (full) mo equiv 30 d[20] = 2 592 000 s
month (Greg av) mo Average Gregorian month = 365242512 d = 30436875 d asymp 26297 times 106 s
month (hollow) mo equiv 29 d[20] = 2 505 600 s
month (synodic) mo Cycle time of moon phases asymp 29530589 days (Average) asymp 2551 times 106 s
octaeteris = 48 mo (full) + 48 mo (hollow) + 3 mo (full)[21] [22] = 8 aof 36525 d = 2922 d
= 2524 608 times 108 s
Planck time equiv (Gℏc5)frac12 asymp 1351 211 868 times 10minus43
s
second s time of 9 192 631 770 periods of the radiation correspondingto the transition between the 2 hyperfine levels of the groundstate of the caesium 133 atom at 0 K[8] (but other secondsare sometimes used in astronomy)
(SI base unit)
shake equiv 10minus8 s = 10 ns
sigma equiv 10minus6 s = 1 μs
Sothic cycle equiv 1 461 a of 365 d = 4607 4096 times 1010 s
svedberg S equiv 10minus13 s = 100 fs
week wk equiv 7 d = 604 800 s
year (Gregorian) a y oryr
= 3652425 d average calculated from common years (365d) plus leap years (366 d) on most years divisible by 4 Seeleap year for details
= 31 556 952 s
year (Julian) a y oryr
= 36525 d average calculated from common years (365 d)plus one leap year (366 d) every four years
= 31 557 600 s
year (sidereal) a y oryr
equiv time taken for Sun to return to the same position withrespect to the stars of the celestial sphere
asymp 365256 363 d asymp 31558 1497632 s
year (tropical) a y oryr
equiv Length of time it takes for the Sun to return to the sameposition in the cycle of seasons
asymp 365242 190 d asymp 31556 925 s
Where UTC is observed the length of timeunits longer than 1 s may increase or decreaseby 1 s if a leap second occurs during the timeinterval of interest
Conversion of units 14
Frequency
Frequency
Name of unit Symbol Definition Relation to SI units
hertz (SI unit) Hz equiv Number of cycles per second = 1 Hz = 1s
revolutions per minute rpm equiv One unit rpm equals one rotation completed around a fixed axis in one minute of time asymp0104719755 rads
Speed or velocity
Speed
Name of unit Symbol Definition Relation to SI units
foot per hour fph equiv 1 fth asymp 8466 667 times 10minus5
ms
foot per minute fpm equiv 1 ftmin = 508 times 10minus3 ms
foot per second fps equiv 1 fts = 3048 times 10minus1 ms
furlong perfortnight
equiv furlongfortnight asymp 1663 095 times 10minus4
ms
inch per minute ipm equiv 1 inmin asymp 423 333 times 10minus4 ms
inch per second ips equiv 1 ins = 254 times 10minus2 ms
mach number M Ratio of the speed to the speed of sound in the medium Varies especially with temperatureAbout 761 mph (1225 kph) in air at sea level to about 660 mph (1062 kph) at jet altitudesUnitless
asymp 340 to 295 ms foraircraft
metre per second(SI unit)
ms equiv 1 ms = 1 ms
mile per hour mph equiv 1 mih = 0447 04 ms
mile per minute mpm equiv 1 mimin = 268224 ms
mile per second mps equiv 1 mis = 1 609344 ms
speed of light invacuum
c equiv 299 792 458 ms = 299 792 458 ms
speed of sound inair
s Varies especially with temperature About 761 mph (1225 kph) in air at sea level to about660 mph (1062 kph) at jet altitudes
asymp 340 to 295 ms ataircraft altitudes
A velocity consists of a speed combined with a direction the speed part of the velocity takes units of speed
Conversion of units 15
Flow (volume)
Flow
Name of unit Symbol Definition Relation to SI units
cubic foot per minute CFM equiv 1 ft3min = 4719474432 times 10minus4 m3s
cubic foot per second ft3s equiv 1 ft3s = 0028316846592 m3s
cubic inch per minute in3min equiv 1 in3min = 27311773 times 10minus7 m3s
cubic inch per second in3s equiv 1 in3s = 16387064 times 10minus5 m3s
cubic metre per second (SIunit)
m3s equiv 1 m3s = 1 m3s
gallon (US fluid) per day GPD equiv 1 gald = 4381263638 times 10minus8 m3s
gallon (US fluid) per hour GPH equiv 1 galh = 1051503273 times 10minus6 m3s
gallon (US fluid) per minute GPM equiv 1 galmin = 630901964 times 10minus5 m3s
litre per minute LPM equiv 1 Lmin = 16 times 10minus5 m3s
Acceleration
Acceleration
Name of unit Symbol Definition Relation to SI units
foot per hour per second fphs equiv 1 ft(hmiddots) asymp 8466 667 times 10minus5
ms2
foot per minute per second fpms equiv 1 ft(minmiddots) = 508 times 10minus3 ms2
foot per second squared fps2 equiv 1 fts2 = 3048 times 10minus1 ms2
gal galileo Gal equiv 1 cms2 = 10minus2 ms2
inch per minute per second ipms equiv 1 in(minmiddots) asymp 4233 333 times 10minus4
ms2
inch per second squared ips2 equiv 1 ins2 = 254 times 10minus2 ms2
knot per second kns equiv 1 kns asymp 5144 444 times 10minus1
ms2
metre per second squared (SI unit) ms2 equiv 1 ms2 = 1 ms2
mile per hour per second mphs equiv 1 mi(hmiddots) = 44704 times 10minus1 ms2
mile per minute per second mpms equiv 1 mi(minmiddots) = 268224 ms2
mile per second squared mps2 equiv 1 mis2 = 1609 344 times 103 ms2
standard gravity g equiv 9806 65 ms2 = 9806 65 ms2
Conversion of units 16
Force
Force
Name of unit Symbol Definition Relation to SI units
atomic unit of force equiv memiddotα2middotc2a0 asymp 8238 722 06 times 10minus8 N
[23]
dyne (cgs unit) dyn equiv gmiddotcms2 = 10minus5 N
kilogram-force kilopondgrave-force
kgf kp Gf equiv g times 1 kg = 9806 65 N
kip kip-force kip kipfklbf
equiv g times 1 000 lb = 4448 221 6152605 times 103 N
milligrave-force gravet-force mGf gf equiv g times 1 g = 9806 65 mN
newton (SI unit) N A force capable of giving a mass of one kg an acceleration of one metreper second per second[24]
= 1 N = 1 kgmiddotms2
ounce-force ozf equiv g times 1 oz = 0278 013 850 9537812 N
pound lb equiv slugmiddotfts2 = 4448 230 531 N
pound-force lbf equiv g times 1 lb = 4448 221 615 2605 N
poise (cgs unit) P equiv 10minus1 Pamiddots = 01 Pamiddots
pound per foot hour lb(ftmiddoth) equiv 1 lb(ftmiddoth) asymp 4133 789 times 10minus4 Pamiddots
pound per foot second lb(ftmiddots) equiv 1 lb(ftmiddots) asymp 1488164 Pamiddots
pound-force second per square foot lbfmiddotsft2 equiv 1 lbfmiddotsft2 asymp 4788026 Pamiddots
pound-force second per square inch lbfmiddotsin2 equiv 1 lbfmiddotsin2 asymp 6894757 Pamiddots
Conversion of units 21
Kinematic viscosity
Kinematic viscosity
Name of unit Symbol Definition Relation to SI units
square foot per second ft2s equiv 1 ft2s = 009290304 m2s
square metre per second (SI unit) m2s equiv 1 m2s = 1 m2s
stokes (cgs unit) St equiv10minus4 m2s
= 10minus4 m2s
Electric current
Electric current
Name of unit Symbol Definition Relation to SI units
ampere (SI base unit) A equiv The constant current needed to produce a force of 2 times 10minus7 newton per metre betweentwo straight parallel conductors of infinite length and negligible circular cross-sectionplaced one metre apart in a vacuum[8]
= 1 A
electromagnetic unitabampere (cgs unit)
abamp equiv 10 A = 10 A
esu per secondstatampere (cgs unit)
esus equiv (01 Amiddotms) c asymp3335641 times 10minus10 A
Electric charge
Electric charge
Name of unit Symbol Definition Relation to SI units
abcoulomb electromagnetic unit (cgsunit)
abC emu equiv 10 C = 10 C
atomic unit of charge au equiv e asymp 1602 176462 times 10minus19 C
coulomb (SI unit) C equiv The amount of electricity carried in one second of time by oneampere of current[24]
= 1 C = 1 Amiddots
faraday F equiv 1 mol times NAmiddote asymp 96 4853383 C
statcoulomb franklin electrostatic unit(cgs unit)
statC Fresu
equiv (01 Amiddotm) c asymp 3335 641 times 10minus10 C
Conversion of units 22
Electric dipole
Electric dipole
Name of unit Symbol Definition Relation to SI units
atomic unit of electric dipole moment ea0 asymp 8478 352 81 times 10minus30
Cmiddotm[28]
Electromotive force electric potential difference
Voltage electromotive force
Name ofunit
Symbol Definition Relation to SI units
abvolt (cgsunit)
abV equiv 1 times 10minus8 V = 1 times 10minus8 V
statvolt (cgsunit)
statV equiv cmiddot (1 μJAmiddotm) = 299792 458 V
volt (SIunit)
V The difference in electric potential across two points along a conducting wire carrying one ampereof constant current when the power dissipated between the points equals one watt[24]
= 1 V = 1 WA = 1kgmiddotm2(Amiddots3)
Electrical resistance
Electrical resistance
Name ofunit
Symbol Definition Relation to SI units
ohm (SIunit)
Ω The resistance between two points in a conductor when one volt of electric potential differenceapplied to these points produces one ampere of current in the conductor[24]
= 1 Ω = 1 VA = 1kgmiddotm2(A2middots3)
Capacitance
Capacitors ability to store charge
Name ofunit
Symbol Definition Relation to SI units
farad (SIunit)
F The capacitance between two parallel plates that results in one volt of potential difference whencharged by one coulomb of electricity[24]
= 1 F = 1 CV = 1A2middots4(kgmiddotm2)
Conversion of units 23
Magnetic flux
magnetic flux
Name of unit Symbol Definition Relation to SI units
maxwell (CGSunit)
Mx equiv 10minus8 Wb[29] = 1 times 10minus8 Wb
weber (SIunit)
Wb Magnetic flux which linking a circuit of one turn would produce in it an electromotive force of1 volt if it were reduced to zero at a uniform rate in 1 second[24]
= 1 Wb = 1 Vmiddots = 1kgmiddotm2(Amiddots2)
Magnetic flux density
What physicists call Magnetic field is called Magnetic flux density by electrical engineersand magnetic induction by applied mathematicians and electrical engineers
Name of unit Symbol Definition Relation to SI units
gauss (CGS unit) G equiv Mxcm2 = 10minus4
T= 1 times 10minus4 T [30]
tesla (SI unit) T equiv Wbm2 = 1 T = 1 Wbm2 = 1kg(Amiddots2)
Inductance
Inductance
Name ofunit
Symbol Definition Relation to SI units
henry (SIunit)
H The inductance of a closed circuit that produces one volt of electromotive force when the current inthe circuit varies at a uniform rate of one ampere per second[24]
= 1 H = 1 WbA = 1kgmiddotm2(Amiddots)2
Temperature
Temperature
Name of unit Symbol Definition Conversion to kelvin
degree Celsius degC degC equiv K minus 27315 [K] equiv [degC] + 27315
degree Delisle degDe [K] = 37315 minus [degDe] times 23
degree Fahrenheit degF degF equiv degC times 95 + 32 [K] equiv ([degF] + 45967) times 59
degree Newton degN [K] = [degN] times 10033 + 27315
degree Rankine degR degRa degR equiv K times 95 [K] equiv [degR] times 59
degree Reacuteaumur degReacute [K] = [degReacute] times 54 + 27315
degree Roslashmer degRoslash [K] = ([degRoslash] minus 75) times 4021 + 27315
kelvin (SI baseunit)
K equiv 127316 of the thermodynamic temperature of the triple point of water[8] equiv 1 K
Conversion of units 24
Information entropy
Information entropy
Name of unit Symbol Definition Relation to SI units Relation to bits
SI unit JK equiv JK = 1 JK
nat nip nepit nat equiv kB = 1380 650 5(23) times 10minus23 JK
bit shannon bit b Sh equiv ln(2) times kB = 9569 940 (16) times 10minus24 JK = 1 bit
ban hartley ban Hart equiv ln(10) times kB = 3179 065 3(53) times 10minus23 JK
nibble equiv 4 bits = 3827 976 0(64) times 10minus23 JK = 22 bit
byte B equiv 8 bits = 7655 952 (13) times 10minus23 JK = 23 bit
kilobyte (decimal) kB equiv 1 000 B = 7655 952 (13) times 10minus20 JK
kilobyte (kibibyte) KB KiB equiv 1 024 B = 7839 695 (13) times 10minus20 JK = 210 bit
Often information entropy is measured in shannons whereas the (discrete) storage space of digital devices ismeasured in bits Thus uncompressed redundant data occupy more than one bit of storage per shannon ofinformation entropy The multiples of a bit listed above are usually used with this meaning Other times the bit isused as a measure of information entropy and is thus a synonym of shannon
Luminous intensityThe candela is the preferred nomenclature for the SI unit
Luminous intensity
Name of unit Symbol Definition Relation toSI units
candela (SI baseunit) candle
cd The luminous intensity in a given direction of a source that emits monochromatic radiation offrequency 540 times 1012 hertz and that has a radiant intensity in that direction of 1683 watt persteradian[8]
= 1 cd
candlepower (new) cp equiv cd The use of candlepower as a unit is discouraged due to its ambiguity = 1 cd
candlepower (oldpre-1948)
cp Varies and is poorly reproducible[31] Approximately 0981 cd[14] asymp 0981 cd
Luminance
Conversion of units 25
Luminance
Name of unit Symbol Definition Relation to SI units
candela per square foot cdft2 equiv cdft2 asymp10763910417 cdm2
candela per square inch cdin2 equiv cdin2 asymp 15500031 cdm2
candela per square metre (SI unit) nit (deprecated[14] ) cdm2 equiv cdm2 = 1 cdm2
Name of unit Symbol Definition Relation to SI units
lumen (SIunit)
lm equiv cdmiddotsr = 1 lm = 1 cdmiddotsr
Illuminance
Illuminance
Name of unit Symbol Definition Relation to SI units
footcandle lumen per square foot fc equiv lmft2 = 10763910417 lx
lumen per square inch lmin2 equiv lmin2 asymp 15500031 lx
lux (SI unit) lx equiv lmm2 = 1 lx = 1 lmm2
phot (CGS unit) ph equiv lmcm2 = 1 times 104 lx
Radiation - source activity
Conversion of units 26
Radioactivity
Name of unit Symbol Definition Relation to SI units
becquerel (SIunit)
Bq equiv Number of disintegrations per second = 1 Bq = 1s
curie Ci equiv 37 times 1010 Bq = 37 times 1010 Bq [32]
rutherford (H) rd equiv 1 MBq = 1 times 106 Bq
Please note that although becquerel (Bq) and hertz (Hz) both ultimately refer to the same SI base unit (sminus1) Hz isused only for periodic phenomena and Bq is only used for stochastic processes associated with radioactivity[33]
Radiation - exposure
Radiation - exposure
Name of unit Symbol Definition Relation to SI units
roentgen R 1 R equiv 258 times 10minus4 Ckg[29] = 258 times 10minus4 Ckg
The roentgen is not a SI unit and the NIST strongly discourages its continued use[34]
Radiation - absorbed dose
Radiation - absorbed dose
Name of unit Symbol Definition Relation to SI units
Name of unit Symbol Definition Relation to SI units
Roumlntgen equivalent man rem equiv 001 Sv = 001 Sv
sievert (SI unit) Sv equiv 1 Jkg[33] = 1 Sv
Although the definitions for sievert (Sv) and gray (Gy) would seem to indicate that they measure the same quantitiesthis is not the case The effect of receiving a certain dose of radiation (given as Gy) is variable and depends on manyfactors thus a new unit was needed to denote the biological effectiveness of that dose on the body this is known asthe equivalent dose and is shown in Sv The general relationship between absorbed dose and equivalent dose can berepresented as
H = Q middot D
where H is the equivalent dose D is the absorbed dose and Q is a dimensionless quality factor Thus for anyquantity of D measured in Gy the numerical value for H measured in Sv may be different[36]
Conversion of units 27
Software toolsHome and office computers come with converters in bundled spreadsheet applications or can access free convertersvia the Internet Units and measurements can be easily converted using these tools but only if the units are explicitlydefined and the conversion is compatible (eg cmHg to kPa)
Free conversion softwarebull Units (software) a popular cross-platform command-line utilitybull Converter [37] contextual unit converter for Mozilla Firefox browsersbull Converber [38] portable application converting utilitybull calculla [39] calculla - online web convertersbull iMetrix [40] - unit converter for xpbull uniteasy [41] online scientific unit conversionbull Unit Converter Add-in for Excel [42] - allow a large selection of unit conversions within the Microsoft Excel
spread sheet programbull Unit Converter [43] simple and extensible unit converterbull Portable Unit Converter [44] including 4500 units 33 unit-categories and the possibility to create custom units
General commercial sources of convertersbull Advanced electronic calculators have unit-conversion functionalitybull Spreadsheet programs usually provide conversion functions or formulas or the user can write their ownbull Commercial mathematical scientific and technical applications often include converters
See also
bull Accuracy and precisionbull English unitsbull False precisionbull Imperial unitsbull International System of Unitsbull Mesures usuellesbull Metric system
bull Natural unitsbull Roundingbull Significant figuresbull Temperature conversionbull United States customary unitsbull Units conversion by factor-labelbull Units of measurement
External linksbull British law Units of measurement regulations 1995 [45]
bull ConvertBuster [46] Variety of conversion tools to convert easilybull How Many A dictionary of units of measurement [47]
bull NIST Fundamental physical constants mdash Non-SI units [48]PDF (357 KB)bull NIST Guide to SI Units [49] Many conversion factors listedbull Online Conversion Calculators [50] Very extensive list of conversions from-to equvalent unitsbull The Unified Code for Units of Measure [51]
bull Units Symbols and Conversions XML Dictionary [52]
bull Multilingual Online Conversion of Units [53]
bull Temperature Converter [54]
Conversion of units 28
References[1] United States Naval Observatory (2009) Selected Astronomical Constants 2009 (http asa usno navy mil SecK 2009
Astronomical_Constants_2009 txt) Accessed May 10 2009[2] NIST Reference on Constants Units and Uncertainty (http physics nist gov cgi-bin cuu Valuebohrrada0|search_for=Bohr+
radius)(2006) National Institute of Standards and Technology Retrieved February 22 2008[3] National Institute of Standards and Technology General Tables of Units of Measurement (http ts nist gov WeightsAndMeasures
Publications appxc cfm)[4] Lide D (Ed) (1990) Handbook of Chemistry and Physics (71st ed) Boca Raton FL CRC Press Section 1[5] National Bureau of Standards (June 30 1959) Refinement of values for the yard and the pound Federal Register viewed September 20
2006 at National Geodetic Survey web site (http www ngs noaa gov PUBS_LIB FedRegister FRdoc59-5442 pdf)[6] The International Astronomical Union and Astronomical Units (http www iau org public_press themes measuring )[7] Klein Herbert Arthur (1988) The Science of Measurement a Historical Survey Mineola NY Dover Publications 0-4862-5839-4[8] The International System of Units Section 21 (http www bipm org en si si_brochure chapter2 2-1 ) (8 ed) Bureau International des
Poids et Mesures 2006 retrieved August 26 2009[9] International System of Units (http www bipm org en si si_brochure chapter4 table8 html) 8th ed (2006) Bureau International des
Poids et Mesures Section 41 Table 8[10] P Kenneth Seidelmann Ed (1992) Explanatory Supplement to the Astronomical Almanac Sausalito CA University Science Books p 716
and sv parsec in Glossary[11] Whitelaw Ian (2007) A Measure of All Things The Story of Man and Measurement (http books google com
booksid=3zgGEWM5-iAC) New York Macmillan 0-312-37026-1 p 152[12] De Vinne Theodore Low (1900) The practice of typography a treatise on the processes of type-making the point system the names sizes
styles and prices of plain printing types (http books google com booksid=R4-DjphIpLMC) 2nd ed New York The Century Co p142ndash150
[13] Pasko Wesley Washington (1894) American dictionary of printing and bookmaking (http books google combooksid=Z_QUAAAAIAAJ) (1894) New York Howard Lockwood p 521
[14] Rowlett Russ (2005) How Many A Dictionary of Units of Measurement (http www unc edu ~rowlett units index html)[15] Thompson A and Taylor BN (2008) Guide for the Use of the International System of Units (SI) National Institute of Standards and
Technology Special Publication 811 p 57[16] US Code of Federal Regulations Title 21 Section 1019 Paragraph (b)(5)(viii) (http ecfr gpoaccess gov cgi t text text-idxc=ecframp
rgn=div8amp view=textamp node=212 0 1 1 2 1 1 6amp idno=21) retrieved August 29 2009[17] Barry N Taylor Ed NIST Special Publication 330 The International System of Units (SI) (http physics nist gov Pubs SP330 sp330
pdf) (2001 Edition) Washington US Government Printing Office 43The 12th Conference Generale des Poids et Mesures(CGPM)hellipdeclares that the word ldquolitrerdquo may be employed as a special name for the cubic decimetre
[18] CODATA Value atomic uint of mass (http physics nist gov cgi-bin cuu Valuettme|search_for=atomic+ unit+ of+ mass) (2006)National Institute of Standards and Technology Retrieved 16 September 2008
[19] The Swiss Federal Office for Metrology gives Zentner on a German language web page (http www metas ch de scales systemch html)and quintal on the English translation of that page (http www metas ch en scales systemch html) the unit is marked speacutecifiquementsuisse
[20] Pedersen O (1983) Glossary in Coyne G Hoskin M and Pedersen O Gregorian Reform of the Calendar Proceedings of the VaticanConference to Commemorate its 400th Anniversary Vatican Observatory Available from Astrophysics Data System
[21] Richards EG (1998) Mapping Time Oxford University Press pp 94ndash95 ISBN 0-19-850413-6[22] Steel Duncan (2000) Marking Time John Wiley amp Sons p 46 ISBN 0-471-29827-1[23] CODATA Value atomic unit of force (http physics nist gov cuu Constants ) (2006) National Institute of Standards and Technology
Retrieved September 14 2008[24] [[Comiteacute International des Poids et Mesures (http www bipm org en CIPM db 1946 2 )] Resolution 2] 1946 retrieved August 26
2009[25] Barry N Taylor (April 1995) Guide for the Use of the International System of Units (SI) (http physics nist gov cuu pdf sp811 pdf)
(NIST Special Publication 811) Washington DC US Government Printing Office pp 57ndash68[26] Barry N Taylor (April 1995) Guide for the Use of the International System of Units (SI) (NIST Special Publication 811) Washington DC
US Government Printing Office p 5[27] International System of Units (http www bipm org en si si_brochure chapter4 table7 html) 8th ed (2006) Bureau International des
Poids et Mesures Section 41 Table 7[28] The NIST Reference on Constants Units and Uncertainty (http physics nist gov cgi-bin cuu Valueauedm) 2006 retrieved August
26 2009[29] NIST Guide to SI Units Appendix B9 (http physics nist gov Pubs SP811 appenB9 html) retrieved August 27 2009[30] Standard for the Use of the International System of Units (SI) The Modern Metric System IEEEASTM SI 10-1997 (1997) New York and
West Conshohocken PA Institute of Electrical and Electronics Engineers and American Society for Testing and Materials Tables A1through A5
Conversion of units 29
[31] The NIST Reference on Constants Units and Uncertainty (http physics nist gov cuu Units candela html) retrieved August 28 2009[32] Ambler Thompson amp Barry N Taylor (2008) Guide for the Use of the International System of Units (SI) (http physics nist gov cuu
pdf sp811 pdf) Special Publication 811 Gaithersburg MD National Institute of Standards and Technology p 10[33] The International System of Units Section 222 Table 3 (http www bipm org en si si_brochure chapter2 2-2 table3 html) (8 ed)
Bureau International des Poids et Mesures 2006 retrieved August 27 2009[34] The NIST Guide to the SI (Special Publication 811) section 52 (http physics nist gov Pubs SP811 sec05 html5 2) 2008 retrieved
August 27 2009[35] Ambler Thompson amp Barry N Taylor (2008) Guide for the Use of the International System of Units (SI) (http physics nist gov cuu
pdf sp811 pdf) Special Publication 811 Gaithersburg MD National Institute of Standards and Technology p 5[36] [[Comiteacute international des poids et mesures (http www bipm org en CIPM db 2002 2 )] 2002 Recommendation 2] retrieved
August 27 2009[37] http converter mozdev org[38] http www xyntec com converber htm[39] http www calculla com[40] http illusions hu index phptask=100amp lang=0amp statpage=86[41] http www uniteasy com[42] http www tenderwire com wikipedialandingpage[43] http www kamlex com index phpoption=com_contentamp view=articleamp id=53amp Itemid=55[44] http www sttmedia com unitconverter[45] http www hmso gov uk si si1995 Uksi_19951804_en_2 htm[46] http www convertbuster com[47] http www unc edu ~rowlett units[48] http physics nist gov cuu Document nonsi_in_1998 pdf[49] http physics nist gov Pubs SP811 appenB9 html[50] http www onlineconversion com[51] http aurora rg iupui edu ~schadow units UCUM ucum html[52] http www posc org refs poscUnits20 xml[53] http www imperialtometric com[54] http www tampile com
Article Sources and Contributors 30
Article Sources and ContributorsConversion of units Source httpenwikipediaorgwindexphpoldid=373975089 Contributors 1571781xxx 7 A-giau AVSI Acather96 Ahoerstemeier Alexius08 Altenmann AndreEngels Andrewa Andy120290 Anonymi Ariconte Army1987 ArnoldReinhold Arthur3030 Aspects AxelBoldt AzaToth Azikala BW95 Bdesham Beland Bensaccount Bkumartvm Blackand White BlaiseFEgan BlueEarth Bobblewik Borbrav Bpmullins Bryan Derksen C J B Scholten CORNELIUSSEON CTZMSC3 Calltech Camerajohn Chaosfeary Charles MatthewsChris the speller Cmdrjameson Colonies Chris Conversion script Cope555 Crappy13 Crissov CyrilB DARTH SIDIOUS 2 DMacks DanielCD Dark Formal DarkestSideX DekisugiDenelson83 Dhp1080 Dicklyon DirkvdM Donald Duck Donarreiskoffer Dramatic Dyss DAringsbquougosz Egil Ehrenkater Ejohnsonboulder Elexmax Elf Emokhberi Enon Eob Epbr123Euchiasmus Fathead99 Father Goose Fella22 Femto FernandoAC Fibula Flutefreek Fred Bauder Fredrik Fuhghettaboutit Fuzheado Gaff Gene Nygaard Georgiy1996 Gerry AshtonGiftlite Gilliam Glenn L GoingBatty Goobergunch Gregsexton Greyengine5 Grunt Gurch Gutza HLHJ Haemo Hammersbach Heracles31 Herbee Heron HikerBush Hqb IcairnsIgiffin Indefatigable Isis JBobbitt JHunterJ Jabowery JakeVortex Jamicanmonkey Jason Begin Jay Jc3s5h Jcronen1 Jdoherty Jeffz1 Jeronimo Jimmuhk Jimp Jimwilliams57 JoeinwapJohndburger Josh Parris Jq4bagiq Kaihsu KaneWang Keenan Pepper Kevin Rector KeyStorm Khukri Kurtan Lee Daniel Crocker LightYear Linuxoidoz Liv4christ210 Loggie Lolo252Lupinelawyer M ichaeligl MJCdetroit MTC Mac MacMcF Magore Markus Kuhn Masterqwe MaxHund Maxamegalon2000 Mbeychok Meggar Mh26 Michael Daly Michael Hardy MichelAudy Mikelifeguard Mikhailov Kusserow Mindbuilder Missvain Monger Mr bulow MrOllie MrZhuKeeper Muro de Aguas Mwanner Mwtoews Nandesuka Natkeeran Ndsg NgjaimeNhy67ygv Nick Y Nick123 NickPenguin Ninjagecko Noe Nosilleg Now3r3 Obelix homologator Oldadamml Oleg Alexandrov Olivier Ortolan88 OwenBlacker Pac72 PassargeaPatrick Paul Martin Peter Horn Physchim62 Piels Pierdm Pmanderson Prometheus235 Quadell QuantumEleven Quod erat demonstrandum 314159 Radagast83 Rccoms RedWolfReinyday Revipm Rexparry sydney Reyk Rhetth Rhialto Rich Farmbrough Richard Myers Rjwilmsi Rlsheehan Robin Barry RoySmith Rpwolfgram SD6-Agent SGBailey SamuelLowry Samw Sander123 Seabhcan SebastianHelm Sherbert1 Shinhan Shrew Sietse Snel SimonP Sinbaddasail0r Skotte Smalljim SomeHuman Spencer Srleffler StarwarsmastergeekSteacoon StefanK SteveRamone Stevertigo Stokerm Suisui Sunev Superboy112233 Superm401 Synchronism Tacoman1996 Tarquin Taw Teratornis The Man in Question ThierrycThingg Thinking of England Thunderbird2 Timwi Tobias Hoevekamp Tomasr Tonsofpcs Toon05 Topsykretts2512 Trekphiler Tuwile Twanvl Uday147502 Unitman00 UrhixidurUtherSRG Vargenau Vsmith WarrenPlatts Wasell Welsh Whispering Wikinger Wolfkeeper Wtmitchell XJamRastafire Xenonice Yath Zginder Zibem Zocky Zotel 713 anonymousedits
Name of unit Symbol Definition Relation to SIunits
angular mil micro equiv 2π6400 rad asymp 0981 748 times 10minus3
rad
arcminute equiv 1deg60 asymp 0290 888 times 10minus3
rad
arcsecond equiv 1deg3600 asymp 4848 137 times 10minus6
rad
centesimal minuteof arc
equiv 1 grad100 asymp 0157 080 times 10minus3
rad
centesimal secondof arc
equiv 1 grad(10 000) asymp 1570 796 times 10minus6
rad
degree (of arc) deg equiv 1360 of a revolution equiv π180 rad asymp 17453293 times 10minus3 rad
grad gradian gon grad equiv 1400 of a revolution equiv 2π400 rad equiv 09deg asymp 15707963 times 10minus3 rad
octant equiv 45deg asymp 0785 398 rad
quadrant equiv 90deg asymp 1570 796 rad
radian (SI unit) rad The angle subtended at the center of a circle by an arc whose length is equal to the circlesradius One full revolution encompasses 2π radians
= 1 rad
sextant equiv 60deg asymp 1047 198 rad
sign equiv 30deg asymp 0523 599 rad
Conversion of units 10
Solid angle
Solid angle
Name of unit Symbol Definition Relation to SIunits
steradian (SIunit)
sr The solid angle subtended at the center of a sphere of radius r by a portion of the surface of the spherehaving an area r2 A sphere encompasses 4π sr[14]
= 1 sr
MassNotesbull See Weight for detail of massweight distinction and conversionbull In this table the unit gee is used to denote standard gravity in order to avoid confusion with the g symbol for
gramsbull In physics the pound of mass is sometimes written lbm to distinguish it from the pound-force (lbf) It should not
be read as the mongrel unit pound metre
Mass
Name of unit Symbol Definition Relation to SI units
atomic mass unit unified u AMU asymp 1660 538 73 times 10minus27 plusmn 13 times 10minus36 kg
atomic unit of mass electron restmass
me asymp 9109 382 15 times 10minus31 plusmn 45 times 10minus39 kg[18]
bag (coffee) equiv 60 kg = 60 kg
bag (Portland cement) equiv 94 lb av = 42637 682 78 kg
barge equiv 22frac12 sh tn = 20 411656 65 kg
carat kt equiv 3 16 gr asymp 205196 548 333 mg
carat (metric) ct equiv 200 mg = 200 mg
clove equiv 8 lb av = 3628 738 96 kg
crith asymp 899349 mg
dalton Da asymp 1660 902 10 times 10minus27 plusmn 13 times 10minus36 kg
dram (apothecary troy) dr t equiv 60 gr = 3887 9346 g
dram (avoirdupois) dr av equiv 27 1132 gr = 1771 845 195 3125 g
electronvolt eV equiv 1 eV (energy unit) c2 = 17826 times 10minus36 kg
gamma γ equiv 1 μg = 1 μg
grain gr equiv 17000 lb av equiv 64798 91 mg
grave G grave was the original name of the kilogram equiv 1 kg
hundredweight (long) long cwt orcwt
equiv 112 lb av = 50802 345 44 kg
hundredweight (short) cental sh cwt equiv 100 lb av = 45359 237 kg
hyl (CGS unit) equiv 1 gee times 1 g times 1 s2m = 9806 65 g
hyl (MKS unit) equiv 1 gee times 1 kg times 1 s2m = 9806 65 kg
Conversion of units 11
kilogram kg equiv mass of the prototype near Paris (asymp mass of 1L ofwater)
equiv 1 kg (SI base unit)[8]
kip kip equiv 1000 lb av = 453592 37 kg
mark equiv 8 oz t = 248827 8144 g
mite equiv 120 gr = 3239 9455 mg
mite (metric) equiv 120 g = 50 mg
ounce (apothecary troy) oz t equiv 112 lb t = 31103 4768 g
ounce (avoirdupois) oz av equiv 116 lb = 28349 523 125 g
ounce (US food nutritionlabeling)
oz equiv 28 g[16] = 28 g
pennyweight dwt pwt equiv 120 oz t = 1555 173 84 g
point equiv 1100 ct = 2 mg
pound (avoirdupois) lb av equiv 0453 592 37 kg = 7000 grains equiv 0453 592 37 kg
pound (metric) equiv 500 g = 500 g
pound (troy) lb t equiv 5 760 grains = 0373 241 7216 kg
quarter (Imperial) equiv 14 long cwt = 2 st = 28 lb av = 12700 586 36 kg
quarter (informal) equiv frac14 short tn = 226796 185 kg
quarter long (informal) equiv frac14 long tn = 254011 7272 kg
quintal (metric) q equiv 100 kg = 100 kg
scruple (apothecary) s ap equiv 20 gr = 1295 9782 g
sheet equiv 1700 lb av = 6479891 mg
slug geepound slug equiv 1 gee times 1 lb av times 1 s2ft asymp 14593 903 kg
stone st equiv 14 lb av = 6350 293 18 kg
ton assay (long) AT equiv 1 mg times 1 long tn divide 1 oz t asymp 32666 667 g
ton assay (short) AT equiv 1 mg times 1 sh tn divide 1 oz t asymp 29166 667 g
ton long long tn or ton equiv 2 240 lb = 1 016046 9088 kg
ton short sh tn equiv 2 000 lb = 907184 74 kg
tonne (mts unit) t equiv 1 000 kg = 1 000 kg
wey equiv 252 lb = 18 st = 114305 277 24 kg (variants exist)
Zentner Ztr Definitions vary see [19] and[14]
Density
Conversion of units 12
Density
Name of unit Symbol Definition Relation to SI units
gram per millilitre gmL equiv gmL = 1000 kgm3
kilogram per cubic metre (SI unit) kgm3 equiv kgm3 = 1 kgm3
slug per cubic foot slugft3 equiv slugft3 asymp 5153788184 kgm3
Time
Time t
Name of unit Symbol Definition Relation to SI units
atomic unit of time au equiv a0(αmiddotc) asymp 2418 884 254 times 10minus17
s
Callippic cycle equiv 441 mo (hollow) + 499 mo (full) = 76 a of 36525 d = 2398 3776 times 109 s
century c equiv 100 a (see below for definition of year length) = 100 times year
day d = 24 h = 86400 s
day (sidereal) d equiv Time needed for the Earth to rotate once around its axisdetermined from successive transits of a very distantastronomical object across an observers meridian(International Celestial Reference Frame)
asymp 86 1641 s
decade dec equiv 10 a (see below for definition of year length) = 10 times year
fortnight fn equiv 2 wk = 1 209 600 s
helek equiv 11 080 h = 33 s
Hipparchic cycle equiv 4 Callippic cycles - 1 d = 9593 424 times 109 s
hour h equiv 60 min = 3 600 s
jiffy j equiv 160 s = 016 s
jiffy (alternate) ja equiv 1100 s = 10 ms
ke (quarter of an hour) equiv frac14 h = 196 d = 60 times 60 4 s = 900 s= 60 4 min = 15 min
Conversion of units 13
ke (traditional) equiv 1100 d = 24 times 60 times 60 100 s =864 s = 24 60 100min = 144 min
lustre lustrum equiv 5 a of 365 d = 15768 times 108 s
Metonic cycle enneadecaeteris equiv 110 mo (hollow) + 125 mo (full) = 6940 d asymp 19 a = 5996 16 times 108 s
millennium equiv 1 000 a (see below for definition of year length) = 1000 times year
milliday md equiv 11 000 d = 24 times 60 times 60 1 000 s= 864 s
minute min equiv 60 s due to leap seconds sometimes 59 s or 61 s = 60 s
moment equiv 90 s = 90 s
month (full) mo equiv 30 d[20] = 2 592 000 s
month (Greg av) mo Average Gregorian month = 365242512 d = 30436875 d asymp 26297 times 106 s
month (hollow) mo equiv 29 d[20] = 2 505 600 s
month (synodic) mo Cycle time of moon phases asymp 29530589 days (Average) asymp 2551 times 106 s
octaeteris = 48 mo (full) + 48 mo (hollow) + 3 mo (full)[21] [22] = 8 aof 36525 d = 2922 d
= 2524 608 times 108 s
Planck time equiv (Gℏc5)frac12 asymp 1351 211 868 times 10minus43
s
second s time of 9 192 631 770 periods of the radiation correspondingto the transition between the 2 hyperfine levels of the groundstate of the caesium 133 atom at 0 K[8] (but other secondsare sometimes used in astronomy)
(SI base unit)
shake equiv 10minus8 s = 10 ns
sigma equiv 10minus6 s = 1 μs
Sothic cycle equiv 1 461 a of 365 d = 4607 4096 times 1010 s
svedberg S equiv 10minus13 s = 100 fs
week wk equiv 7 d = 604 800 s
year (Gregorian) a y oryr
= 3652425 d average calculated from common years (365d) plus leap years (366 d) on most years divisible by 4 Seeleap year for details
= 31 556 952 s
year (Julian) a y oryr
= 36525 d average calculated from common years (365 d)plus one leap year (366 d) every four years
= 31 557 600 s
year (sidereal) a y oryr
equiv time taken for Sun to return to the same position withrespect to the stars of the celestial sphere
asymp 365256 363 d asymp 31558 1497632 s
year (tropical) a y oryr
equiv Length of time it takes for the Sun to return to the sameposition in the cycle of seasons
asymp 365242 190 d asymp 31556 925 s
Where UTC is observed the length of timeunits longer than 1 s may increase or decreaseby 1 s if a leap second occurs during the timeinterval of interest
Conversion of units 14
Frequency
Frequency
Name of unit Symbol Definition Relation to SI units
hertz (SI unit) Hz equiv Number of cycles per second = 1 Hz = 1s
revolutions per minute rpm equiv One unit rpm equals one rotation completed around a fixed axis in one minute of time asymp0104719755 rads
Speed or velocity
Speed
Name of unit Symbol Definition Relation to SI units
foot per hour fph equiv 1 fth asymp 8466 667 times 10minus5
ms
foot per minute fpm equiv 1 ftmin = 508 times 10minus3 ms
foot per second fps equiv 1 fts = 3048 times 10minus1 ms
furlong perfortnight
equiv furlongfortnight asymp 1663 095 times 10minus4
ms
inch per minute ipm equiv 1 inmin asymp 423 333 times 10minus4 ms
inch per second ips equiv 1 ins = 254 times 10minus2 ms
mach number M Ratio of the speed to the speed of sound in the medium Varies especially with temperatureAbout 761 mph (1225 kph) in air at sea level to about 660 mph (1062 kph) at jet altitudesUnitless
asymp 340 to 295 ms foraircraft
metre per second(SI unit)
ms equiv 1 ms = 1 ms
mile per hour mph equiv 1 mih = 0447 04 ms
mile per minute mpm equiv 1 mimin = 268224 ms
mile per second mps equiv 1 mis = 1 609344 ms
speed of light invacuum
c equiv 299 792 458 ms = 299 792 458 ms
speed of sound inair
s Varies especially with temperature About 761 mph (1225 kph) in air at sea level to about660 mph (1062 kph) at jet altitudes
asymp 340 to 295 ms ataircraft altitudes
A velocity consists of a speed combined with a direction the speed part of the velocity takes units of speed
Conversion of units 15
Flow (volume)
Flow
Name of unit Symbol Definition Relation to SI units
cubic foot per minute CFM equiv 1 ft3min = 4719474432 times 10minus4 m3s
cubic foot per second ft3s equiv 1 ft3s = 0028316846592 m3s
cubic inch per minute in3min equiv 1 in3min = 27311773 times 10minus7 m3s
cubic inch per second in3s equiv 1 in3s = 16387064 times 10minus5 m3s
cubic metre per second (SIunit)
m3s equiv 1 m3s = 1 m3s
gallon (US fluid) per day GPD equiv 1 gald = 4381263638 times 10minus8 m3s
gallon (US fluid) per hour GPH equiv 1 galh = 1051503273 times 10minus6 m3s
gallon (US fluid) per minute GPM equiv 1 galmin = 630901964 times 10minus5 m3s
litre per minute LPM equiv 1 Lmin = 16 times 10minus5 m3s
Acceleration
Acceleration
Name of unit Symbol Definition Relation to SI units
foot per hour per second fphs equiv 1 ft(hmiddots) asymp 8466 667 times 10minus5
ms2
foot per minute per second fpms equiv 1 ft(minmiddots) = 508 times 10minus3 ms2
foot per second squared fps2 equiv 1 fts2 = 3048 times 10minus1 ms2
gal galileo Gal equiv 1 cms2 = 10minus2 ms2
inch per minute per second ipms equiv 1 in(minmiddots) asymp 4233 333 times 10minus4
ms2
inch per second squared ips2 equiv 1 ins2 = 254 times 10minus2 ms2
knot per second kns equiv 1 kns asymp 5144 444 times 10minus1
ms2
metre per second squared (SI unit) ms2 equiv 1 ms2 = 1 ms2
mile per hour per second mphs equiv 1 mi(hmiddots) = 44704 times 10minus1 ms2
mile per minute per second mpms equiv 1 mi(minmiddots) = 268224 ms2
mile per second squared mps2 equiv 1 mis2 = 1609 344 times 103 ms2
standard gravity g equiv 9806 65 ms2 = 9806 65 ms2
Conversion of units 16
Force
Force
Name of unit Symbol Definition Relation to SI units
atomic unit of force equiv memiddotα2middotc2a0 asymp 8238 722 06 times 10minus8 N
[23]
dyne (cgs unit) dyn equiv gmiddotcms2 = 10minus5 N
kilogram-force kilopondgrave-force
kgf kp Gf equiv g times 1 kg = 9806 65 N
kip kip-force kip kipfklbf
equiv g times 1 000 lb = 4448 221 6152605 times 103 N
milligrave-force gravet-force mGf gf equiv g times 1 g = 9806 65 mN
newton (SI unit) N A force capable of giving a mass of one kg an acceleration of one metreper second per second[24]
= 1 N = 1 kgmiddotms2
ounce-force ozf equiv g times 1 oz = 0278 013 850 9537812 N
pound lb equiv slugmiddotfts2 = 4448 230 531 N
pound-force lbf equiv g times 1 lb = 4448 221 615 2605 N
poise (cgs unit) P equiv 10minus1 Pamiddots = 01 Pamiddots
pound per foot hour lb(ftmiddoth) equiv 1 lb(ftmiddoth) asymp 4133 789 times 10minus4 Pamiddots
pound per foot second lb(ftmiddots) equiv 1 lb(ftmiddots) asymp 1488164 Pamiddots
pound-force second per square foot lbfmiddotsft2 equiv 1 lbfmiddotsft2 asymp 4788026 Pamiddots
pound-force second per square inch lbfmiddotsin2 equiv 1 lbfmiddotsin2 asymp 6894757 Pamiddots
Conversion of units 21
Kinematic viscosity
Kinematic viscosity
Name of unit Symbol Definition Relation to SI units
square foot per second ft2s equiv 1 ft2s = 009290304 m2s
square metre per second (SI unit) m2s equiv 1 m2s = 1 m2s
stokes (cgs unit) St equiv10minus4 m2s
= 10minus4 m2s
Electric current
Electric current
Name of unit Symbol Definition Relation to SI units
ampere (SI base unit) A equiv The constant current needed to produce a force of 2 times 10minus7 newton per metre betweentwo straight parallel conductors of infinite length and negligible circular cross-sectionplaced one metre apart in a vacuum[8]
= 1 A
electromagnetic unitabampere (cgs unit)
abamp equiv 10 A = 10 A
esu per secondstatampere (cgs unit)
esus equiv (01 Amiddotms) c asymp3335641 times 10minus10 A
Electric charge
Electric charge
Name of unit Symbol Definition Relation to SI units
abcoulomb electromagnetic unit (cgsunit)
abC emu equiv 10 C = 10 C
atomic unit of charge au equiv e asymp 1602 176462 times 10minus19 C
coulomb (SI unit) C equiv The amount of electricity carried in one second of time by oneampere of current[24]
= 1 C = 1 Amiddots
faraday F equiv 1 mol times NAmiddote asymp 96 4853383 C
statcoulomb franklin electrostatic unit(cgs unit)
statC Fresu
equiv (01 Amiddotm) c asymp 3335 641 times 10minus10 C
Conversion of units 22
Electric dipole
Electric dipole
Name of unit Symbol Definition Relation to SI units
atomic unit of electric dipole moment ea0 asymp 8478 352 81 times 10minus30
Cmiddotm[28]
Electromotive force electric potential difference
Voltage electromotive force
Name ofunit
Symbol Definition Relation to SI units
abvolt (cgsunit)
abV equiv 1 times 10minus8 V = 1 times 10minus8 V
statvolt (cgsunit)
statV equiv cmiddot (1 μJAmiddotm) = 299792 458 V
volt (SIunit)
V The difference in electric potential across two points along a conducting wire carrying one ampereof constant current when the power dissipated between the points equals one watt[24]
= 1 V = 1 WA = 1kgmiddotm2(Amiddots3)
Electrical resistance
Electrical resistance
Name ofunit
Symbol Definition Relation to SI units
ohm (SIunit)
Ω The resistance between two points in a conductor when one volt of electric potential differenceapplied to these points produces one ampere of current in the conductor[24]
= 1 Ω = 1 VA = 1kgmiddotm2(A2middots3)
Capacitance
Capacitors ability to store charge
Name ofunit
Symbol Definition Relation to SI units
farad (SIunit)
F The capacitance between two parallel plates that results in one volt of potential difference whencharged by one coulomb of electricity[24]
= 1 F = 1 CV = 1A2middots4(kgmiddotm2)
Conversion of units 23
Magnetic flux
magnetic flux
Name of unit Symbol Definition Relation to SI units
maxwell (CGSunit)
Mx equiv 10minus8 Wb[29] = 1 times 10minus8 Wb
weber (SIunit)
Wb Magnetic flux which linking a circuit of one turn would produce in it an electromotive force of1 volt if it were reduced to zero at a uniform rate in 1 second[24]
= 1 Wb = 1 Vmiddots = 1kgmiddotm2(Amiddots2)
Magnetic flux density
What physicists call Magnetic field is called Magnetic flux density by electrical engineersand magnetic induction by applied mathematicians and electrical engineers
Name of unit Symbol Definition Relation to SI units
gauss (CGS unit) G equiv Mxcm2 = 10minus4
T= 1 times 10minus4 T [30]
tesla (SI unit) T equiv Wbm2 = 1 T = 1 Wbm2 = 1kg(Amiddots2)
Inductance
Inductance
Name ofunit
Symbol Definition Relation to SI units
henry (SIunit)
H The inductance of a closed circuit that produces one volt of electromotive force when the current inthe circuit varies at a uniform rate of one ampere per second[24]
= 1 H = 1 WbA = 1kgmiddotm2(Amiddots)2
Temperature
Temperature
Name of unit Symbol Definition Conversion to kelvin
degree Celsius degC degC equiv K minus 27315 [K] equiv [degC] + 27315
degree Delisle degDe [K] = 37315 minus [degDe] times 23
degree Fahrenheit degF degF equiv degC times 95 + 32 [K] equiv ([degF] + 45967) times 59
degree Newton degN [K] = [degN] times 10033 + 27315
degree Rankine degR degRa degR equiv K times 95 [K] equiv [degR] times 59
degree Reacuteaumur degReacute [K] = [degReacute] times 54 + 27315
degree Roslashmer degRoslash [K] = ([degRoslash] minus 75) times 4021 + 27315
kelvin (SI baseunit)
K equiv 127316 of the thermodynamic temperature of the triple point of water[8] equiv 1 K
Conversion of units 24
Information entropy
Information entropy
Name of unit Symbol Definition Relation to SI units Relation to bits
SI unit JK equiv JK = 1 JK
nat nip nepit nat equiv kB = 1380 650 5(23) times 10minus23 JK
bit shannon bit b Sh equiv ln(2) times kB = 9569 940 (16) times 10minus24 JK = 1 bit
ban hartley ban Hart equiv ln(10) times kB = 3179 065 3(53) times 10minus23 JK
nibble equiv 4 bits = 3827 976 0(64) times 10minus23 JK = 22 bit
byte B equiv 8 bits = 7655 952 (13) times 10minus23 JK = 23 bit
kilobyte (decimal) kB equiv 1 000 B = 7655 952 (13) times 10minus20 JK
kilobyte (kibibyte) KB KiB equiv 1 024 B = 7839 695 (13) times 10minus20 JK = 210 bit
Often information entropy is measured in shannons whereas the (discrete) storage space of digital devices ismeasured in bits Thus uncompressed redundant data occupy more than one bit of storage per shannon ofinformation entropy The multiples of a bit listed above are usually used with this meaning Other times the bit isused as a measure of information entropy and is thus a synonym of shannon
Luminous intensityThe candela is the preferred nomenclature for the SI unit
Luminous intensity
Name of unit Symbol Definition Relation toSI units
candela (SI baseunit) candle
cd The luminous intensity in a given direction of a source that emits monochromatic radiation offrequency 540 times 1012 hertz and that has a radiant intensity in that direction of 1683 watt persteradian[8]
= 1 cd
candlepower (new) cp equiv cd The use of candlepower as a unit is discouraged due to its ambiguity = 1 cd
candlepower (oldpre-1948)
cp Varies and is poorly reproducible[31] Approximately 0981 cd[14] asymp 0981 cd
Luminance
Conversion of units 25
Luminance
Name of unit Symbol Definition Relation to SI units
candela per square foot cdft2 equiv cdft2 asymp10763910417 cdm2
candela per square inch cdin2 equiv cdin2 asymp 15500031 cdm2
candela per square metre (SI unit) nit (deprecated[14] ) cdm2 equiv cdm2 = 1 cdm2
Name of unit Symbol Definition Relation to SI units
lumen (SIunit)
lm equiv cdmiddotsr = 1 lm = 1 cdmiddotsr
Illuminance
Illuminance
Name of unit Symbol Definition Relation to SI units
footcandle lumen per square foot fc equiv lmft2 = 10763910417 lx
lumen per square inch lmin2 equiv lmin2 asymp 15500031 lx
lux (SI unit) lx equiv lmm2 = 1 lx = 1 lmm2
phot (CGS unit) ph equiv lmcm2 = 1 times 104 lx
Radiation - source activity
Conversion of units 26
Radioactivity
Name of unit Symbol Definition Relation to SI units
becquerel (SIunit)
Bq equiv Number of disintegrations per second = 1 Bq = 1s
curie Ci equiv 37 times 1010 Bq = 37 times 1010 Bq [32]
rutherford (H) rd equiv 1 MBq = 1 times 106 Bq
Please note that although becquerel (Bq) and hertz (Hz) both ultimately refer to the same SI base unit (sminus1) Hz isused only for periodic phenomena and Bq is only used for stochastic processes associated with radioactivity[33]
Radiation - exposure
Radiation - exposure
Name of unit Symbol Definition Relation to SI units
roentgen R 1 R equiv 258 times 10minus4 Ckg[29] = 258 times 10minus4 Ckg
The roentgen is not a SI unit and the NIST strongly discourages its continued use[34]
Radiation - absorbed dose
Radiation - absorbed dose
Name of unit Symbol Definition Relation to SI units
Name of unit Symbol Definition Relation to SI units
Roumlntgen equivalent man rem equiv 001 Sv = 001 Sv
sievert (SI unit) Sv equiv 1 Jkg[33] = 1 Sv
Although the definitions for sievert (Sv) and gray (Gy) would seem to indicate that they measure the same quantitiesthis is not the case The effect of receiving a certain dose of radiation (given as Gy) is variable and depends on manyfactors thus a new unit was needed to denote the biological effectiveness of that dose on the body this is known asthe equivalent dose and is shown in Sv The general relationship between absorbed dose and equivalent dose can berepresented as
H = Q middot D
where H is the equivalent dose D is the absorbed dose and Q is a dimensionless quality factor Thus for anyquantity of D measured in Gy the numerical value for H measured in Sv may be different[36]
Conversion of units 27
Software toolsHome and office computers come with converters in bundled spreadsheet applications or can access free convertersvia the Internet Units and measurements can be easily converted using these tools but only if the units are explicitlydefined and the conversion is compatible (eg cmHg to kPa)
Free conversion softwarebull Units (software) a popular cross-platform command-line utilitybull Converter [37] contextual unit converter for Mozilla Firefox browsersbull Converber [38] portable application converting utilitybull calculla [39] calculla - online web convertersbull iMetrix [40] - unit converter for xpbull uniteasy [41] online scientific unit conversionbull Unit Converter Add-in for Excel [42] - allow a large selection of unit conversions within the Microsoft Excel
spread sheet programbull Unit Converter [43] simple and extensible unit converterbull Portable Unit Converter [44] including 4500 units 33 unit-categories and the possibility to create custom units
General commercial sources of convertersbull Advanced electronic calculators have unit-conversion functionalitybull Spreadsheet programs usually provide conversion functions or formulas or the user can write their ownbull Commercial mathematical scientific and technical applications often include converters
See also
bull Accuracy and precisionbull English unitsbull False precisionbull Imperial unitsbull International System of Unitsbull Mesures usuellesbull Metric system
bull Natural unitsbull Roundingbull Significant figuresbull Temperature conversionbull United States customary unitsbull Units conversion by factor-labelbull Units of measurement
External linksbull British law Units of measurement regulations 1995 [45]
bull ConvertBuster [46] Variety of conversion tools to convert easilybull How Many A dictionary of units of measurement [47]
bull NIST Fundamental physical constants mdash Non-SI units [48]PDF (357 KB)bull NIST Guide to SI Units [49] Many conversion factors listedbull Online Conversion Calculators [50] Very extensive list of conversions from-to equvalent unitsbull The Unified Code for Units of Measure [51]
bull Units Symbols and Conversions XML Dictionary [52]
bull Multilingual Online Conversion of Units [53]
bull Temperature Converter [54]
Conversion of units 28
References[1] United States Naval Observatory (2009) Selected Astronomical Constants 2009 (http asa usno navy mil SecK 2009
Astronomical_Constants_2009 txt) Accessed May 10 2009[2] NIST Reference on Constants Units and Uncertainty (http physics nist gov cgi-bin cuu Valuebohrrada0|search_for=Bohr+
radius)(2006) National Institute of Standards and Technology Retrieved February 22 2008[3] National Institute of Standards and Technology General Tables of Units of Measurement (http ts nist gov WeightsAndMeasures
Publications appxc cfm)[4] Lide D (Ed) (1990) Handbook of Chemistry and Physics (71st ed) Boca Raton FL CRC Press Section 1[5] National Bureau of Standards (June 30 1959) Refinement of values for the yard and the pound Federal Register viewed September 20
2006 at National Geodetic Survey web site (http www ngs noaa gov PUBS_LIB FedRegister FRdoc59-5442 pdf)[6] The International Astronomical Union and Astronomical Units (http www iau org public_press themes measuring )[7] Klein Herbert Arthur (1988) The Science of Measurement a Historical Survey Mineola NY Dover Publications 0-4862-5839-4[8] The International System of Units Section 21 (http www bipm org en si si_brochure chapter2 2-1 ) (8 ed) Bureau International des
Poids et Mesures 2006 retrieved August 26 2009[9] International System of Units (http www bipm org en si si_brochure chapter4 table8 html) 8th ed (2006) Bureau International des
Poids et Mesures Section 41 Table 8[10] P Kenneth Seidelmann Ed (1992) Explanatory Supplement to the Astronomical Almanac Sausalito CA University Science Books p 716
and sv parsec in Glossary[11] Whitelaw Ian (2007) A Measure of All Things The Story of Man and Measurement (http books google com
booksid=3zgGEWM5-iAC) New York Macmillan 0-312-37026-1 p 152[12] De Vinne Theodore Low (1900) The practice of typography a treatise on the processes of type-making the point system the names sizes
styles and prices of plain printing types (http books google com booksid=R4-DjphIpLMC) 2nd ed New York The Century Co p142ndash150
[13] Pasko Wesley Washington (1894) American dictionary of printing and bookmaking (http books google combooksid=Z_QUAAAAIAAJ) (1894) New York Howard Lockwood p 521
[14] Rowlett Russ (2005) How Many A Dictionary of Units of Measurement (http www unc edu ~rowlett units index html)[15] Thompson A and Taylor BN (2008) Guide for the Use of the International System of Units (SI) National Institute of Standards and
Technology Special Publication 811 p 57[16] US Code of Federal Regulations Title 21 Section 1019 Paragraph (b)(5)(viii) (http ecfr gpoaccess gov cgi t text text-idxc=ecframp
rgn=div8amp view=textamp node=212 0 1 1 2 1 1 6amp idno=21) retrieved August 29 2009[17] Barry N Taylor Ed NIST Special Publication 330 The International System of Units (SI) (http physics nist gov Pubs SP330 sp330
pdf) (2001 Edition) Washington US Government Printing Office 43The 12th Conference Generale des Poids et Mesures(CGPM)hellipdeclares that the word ldquolitrerdquo may be employed as a special name for the cubic decimetre
[18] CODATA Value atomic uint of mass (http physics nist gov cgi-bin cuu Valuettme|search_for=atomic+ unit+ of+ mass) (2006)National Institute of Standards and Technology Retrieved 16 September 2008
[19] The Swiss Federal Office for Metrology gives Zentner on a German language web page (http www metas ch de scales systemch html)and quintal on the English translation of that page (http www metas ch en scales systemch html) the unit is marked speacutecifiquementsuisse
[20] Pedersen O (1983) Glossary in Coyne G Hoskin M and Pedersen O Gregorian Reform of the Calendar Proceedings of the VaticanConference to Commemorate its 400th Anniversary Vatican Observatory Available from Astrophysics Data System
[21] Richards EG (1998) Mapping Time Oxford University Press pp 94ndash95 ISBN 0-19-850413-6[22] Steel Duncan (2000) Marking Time John Wiley amp Sons p 46 ISBN 0-471-29827-1[23] CODATA Value atomic unit of force (http physics nist gov cuu Constants ) (2006) National Institute of Standards and Technology
Retrieved September 14 2008[24] [[Comiteacute International des Poids et Mesures (http www bipm org en CIPM db 1946 2 )] Resolution 2] 1946 retrieved August 26
2009[25] Barry N Taylor (April 1995) Guide for the Use of the International System of Units (SI) (http physics nist gov cuu pdf sp811 pdf)
(NIST Special Publication 811) Washington DC US Government Printing Office pp 57ndash68[26] Barry N Taylor (April 1995) Guide for the Use of the International System of Units (SI) (NIST Special Publication 811) Washington DC
US Government Printing Office p 5[27] International System of Units (http www bipm org en si si_brochure chapter4 table7 html) 8th ed (2006) Bureau International des
Poids et Mesures Section 41 Table 7[28] The NIST Reference on Constants Units and Uncertainty (http physics nist gov cgi-bin cuu Valueauedm) 2006 retrieved August
26 2009[29] NIST Guide to SI Units Appendix B9 (http physics nist gov Pubs SP811 appenB9 html) retrieved August 27 2009[30] Standard for the Use of the International System of Units (SI) The Modern Metric System IEEEASTM SI 10-1997 (1997) New York and
West Conshohocken PA Institute of Electrical and Electronics Engineers and American Society for Testing and Materials Tables A1through A5
Conversion of units 29
[31] The NIST Reference on Constants Units and Uncertainty (http physics nist gov cuu Units candela html) retrieved August 28 2009[32] Ambler Thompson amp Barry N Taylor (2008) Guide for the Use of the International System of Units (SI) (http physics nist gov cuu
pdf sp811 pdf) Special Publication 811 Gaithersburg MD National Institute of Standards and Technology p 10[33] The International System of Units Section 222 Table 3 (http www bipm org en si si_brochure chapter2 2-2 table3 html) (8 ed)
Bureau International des Poids et Mesures 2006 retrieved August 27 2009[34] The NIST Guide to the SI (Special Publication 811) section 52 (http physics nist gov Pubs SP811 sec05 html5 2) 2008 retrieved
August 27 2009[35] Ambler Thompson amp Barry N Taylor (2008) Guide for the Use of the International System of Units (SI) (http physics nist gov cuu
pdf sp811 pdf) Special Publication 811 Gaithersburg MD National Institute of Standards and Technology p 5[36] [[Comiteacute international des poids et mesures (http www bipm org en CIPM db 2002 2 )] 2002 Recommendation 2] retrieved
August 27 2009[37] http converter mozdev org[38] http www xyntec com converber htm[39] http www calculla com[40] http illusions hu index phptask=100amp lang=0amp statpage=86[41] http www uniteasy com[42] http www tenderwire com wikipedialandingpage[43] http www kamlex com index phpoption=com_contentamp view=articleamp id=53amp Itemid=55[44] http www sttmedia com unitconverter[45] http www hmso gov uk si si1995 Uksi_19951804_en_2 htm[46] http www convertbuster com[47] http www unc edu ~rowlett units[48] http physics nist gov cuu Document nonsi_in_1998 pdf[49] http physics nist gov Pubs SP811 appenB9 html[50] http www onlineconversion com[51] http aurora rg iupui edu ~schadow units UCUM ucum html[52] http www posc org refs poscUnits20 xml[53] http www imperialtometric com[54] http www tampile com
Article Sources and Contributors 30
Article Sources and ContributorsConversion of units Source httpenwikipediaorgwindexphpoldid=373975089 Contributors 1571781xxx 7 A-giau AVSI Acather96 Ahoerstemeier Alexius08 Altenmann AndreEngels Andrewa Andy120290 Anonymi Ariconte Army1987 ArnoldReinhold Arthur3030 Aspects AxelBoldt AzaToth Azikala BW95 Bdesham Beland Bensaccount Bkumartvm Blackand White BlaiseFEgan BlueEarth Bobblewik Borbrav Bpmullins Bryan Derksen C J B Scholten CORNELIUSSEON CTZMSC3 Calltech Camerajohn Chaosfeary Charles MatthewsChris the speller Cmdrjameson Colonies Chris Conversion script Cope555 Crappy13 Crissov CyrilB DARTH SIDIOUS 2 DMacks DanielCD Dark Formal DarkestSideX DekisugiDenelson83 Dhp1080 Dicklyon DirkvdM Donald Duck Donarreiskoffer Dramatic Dyss DAringsbquougosz Egil Ehrenkater Ejohnsonboulder Elexmax Elf Emokhberi Enon Eob Epbr123Euchiasmus Fathead99 Father Goose Fella22 Femto FernandoAC Fibula Flutefreek Fred Bauder Fredrik Fuhghettaboutit Fuzheado Gaff Gene Nygaard Georgiy1996 Gerry AshtonGiftlite Gilliam Glenn L GoingBatty Goobergunch Gregsexton Greyengine5 Grunt Gurch Gutza HLHJ Haemo Hammersbach Heracles31 Herbee Heron HikerBush Hqb IcairnsIgiffin Indefatigable Isis JBobbitt JHunterJ Jabowery JakeVortex Jamicanmonkey Jason Begin Jay Jc3s5h Jcronen1 Jdoherty Jeffz1 Jeronimo Jimmuhk Jimp Jimwilliams57 JoeinwapJohndburger Josh Parris Jq4bagiq Kaihsu KaneWang Keenan Pepper Kevin Rector KeyStorm Khukri Kurtan Lee Daniel Crocker LightYear Linuxoidoz Liv4christ210 Loggie Lolo252Lupinelawyer M ichaeligl MJCdetroit MTC Mac MacMcF Magore Markus Kuhn Masterqwe MaxHund Maxamegalon2000 Mbeychok Meggar Mh26 Michael Daly Michael Hardy MichelAudy Mikelifeguard Mikhailov Kusserow Mindbuilder Missvain Monger Mr bulow MrOllie MrZhuKeeper Muro de Aguas Mwanner Mwtoews Nandesuka Natkeeran Ndsg NgjaimeNhy67ygv Nick Y Nick123 NickPenguin Ninjagecko Noe Nosilleg Now3r3 Obelix homologator Oldadamml Oleg Alexandrov Olivier Ortolan88 OwenBlacker Pac72 PassargeaPatrick Paul Martin Peter Horn Physchim62 Piels Pierdm Pmanderson Prometheus235 Quadell QuantumEleven Quod erat demonstrandum 314159 Radagast83 Rccoms RedWolfReinyday Revipm Rexparry sydney Reyk Rhetth Rhialto Rich Farmbrough Richard Myers Rjwilmsi Rlsheehan Robin Barry RoySmith Rpwolfgram SD6-Agent SGBailey SamuelLowry Samw Sander123 Seabhcan SebastianHelm Sherbert1 Shinhan Shrew Sietse Snel SimonP Sinbaddasail0r Skotte Smalljim SomeHuman Spencer Srleffler StarwarsmastergeekSteacoon StefanK SteveRamone Stevertigo Stokerm Suisui Sunev Superboy112233 Superm401 Synchronism Tacoman1996 Tarquin Taw Teratornis The Man in Question ThierrycThingg Thinking of England Thunderbird2 Timwi Tobias Hoevekamp Tomasr Tonsofpcs Toon05 Topsykretts2512 Trekphiler Tuwile Twanvl Uday147502 Unitman00 UrhixidurUtherSRG Vargenau Vsmith WarrenPlatts Wasell Welsh Whispering Wikinger Wolfkeeper Wtmitchell XJamRastafire Xenonice Yath Zginder Zibem Zocky Zotel 713 anonymousedits
Name of unit Symbol Definition Relation to SIunits
steradian (SIunit)
sr The solid angle subtended at the center of a sphere of radius r by a portion of the surface of the spherehaving an area r2 A sphere encompasses 4π sr[14]
= 1 sr
MassNotesbull See Weight for detail of massweight distinction and conversionbull In this table the unit gee is used to denote standard gravity in order to avoid confusion with the g symbol for
gramsbull In physics the pound of mass is sometimes written lbm to distinguish it from the pound-force (lbf) It should not
be read as the mongrel unit pound metre
Mass
Name of unit Symbol Definition Relation to SI units
atomic mass unit unified u AMU asymp 1660 538 73 times 10minus27 plusmn 13 times 10minus36 kg
atomic unit of mass electron restmass
me asymp 9109 382 15 times 10minus31 plusmn 45 times 10minus39 kg[18]
bag (coffee) equiv 60 kg = 60 kg
bag (Portland cement) equiv 94 lb av = 42637 682 78 kg
barge equiv 22frac12 sh tn = 20 411656 65 kg
carat kt equiv 3 16 gr asymp 205196 548 333 mg
carat (metric) ct equiv 200 mg = 200 mg
clove equiv 8 lb av = 3628 738 96 kg
crith asymp 899349 mg
dalton Da asymp 1660 902 10 times 10minus27 plusmn 13 times 10minus36 kg
dram (apothecary troy) dr t equiv 60 gr = 3887 9346 g
dram (avoirdupois) dr av equiv 27 1132 gr = 1771 845 195 3125 g
electronvolt eV equiv 1 eV (energy unit) c2 = 17826 times 10minus36 kg
gamma γ equiv 1 μg = 1 μg
grain gr equiv 17000 lb av equiv 64798 91 mg
grave G grave was the original name of the kilogram equiv 1 kg
hundredweight (long) long cwt orcwt
equiv 112 lb av = 50802 345 44 kg
hundredweight (short) cental sh cwt equiv 100 lb av = 45359 237 kg
hyl (CGS unit) equiv 1 gee times 1 g times 1 s2m = 9806 65 g
hyl (MKS unit) equiv 1 gee times 1 kg times 1 s2m = 9806 65 kg
Conversion of units 11
kilogram kg equiv mass of the prototype near Paris (asymp mass of 1L ofwater)
equiv 1 kg (SI base unit)[8]
kip kip equiv 1000 lb av = 453592 37 kg
mark equiv 8 oz t = 248827 8144 g
mite equiv 120 gr = 3239 9455 mg
mite (metric) equiv 120 g = 50 mg
ounce (apothecary troy) oz t equiv 112 lb t = 31103 4768 g
ounce (avoirdupois) oz av equiv 116 lb = 28349 523 125 g
ounce (US food nutritionlabeling)
oz equiv 28 g[16] = 28 g
pennyweight dwt pwt equiv 120 oz t = 1555 173 84 g
point equiv 1100 ct = 2 mg
pound (avoirdupois) lb av equiv 0453 592 37 kg = 7000 grains equiv 0453 592 37 kg
pound (metric) equiv 500 g = 500 g
pound (troy) lb t equiv 5 760 grains = 0373 241 7216 kg
quarter (Imperial) equiv 14 long cwt = 2 st = 28 lb av = 12700 586 36 kg
quarter (informal) equiv frac14 short tn = 226796 185 kg
quarter long (informal) equiv frac14 long tn = 254011 7272 kg
quintal (metric) q equiv 100 kg = 100 kg
scruple (apothecary) s ap equiv 20 gr = 1295 9782 g
sheet equiv 1700 lb av = 6479891 mg
slug geepound slug equiv 1 gee times 1 lb av times 1 s2ft asymp 14593 903 kg
stone st equiv 14 lb av = 6350 293 18 kg
ton assay (long) AT equiv 1 mg times 1 long tn divide 1 oz t asymp 32666 667 g
ton assay (short) AT equiv 1 mg times 1 sh tn divide 1 oz t asymp 29166 667 g
ton long long tn or ton equiv 2 240 lb = 1 016046 9088 kg
ton short sh tn equiv 2 000 lb = 907184 74 kg
tonne (mts unit) t equiv 1 000 kg = 1 000 kg
wey equiv 252 lb = 18 st = 114305 277 24 kg (variants exist)
Zentner Ztr Definitions vary see [19] and[14]
Density
Conversion of units 12
Density
Name of unit Symbol Definition Relation to SI units
gram per millilitre gmL equiv gmL = 1000 kgm3
kilogram per cubic metre (SI unit) kgm3 equiv kgm3 = 1 kgm3
slug per cubic foot slugft3 equiv slugft3 asymp 5153788184 kgm3
Time
Time t
Name of unit Symbol Definition Relation to SI units
atomic unit of time au equiv a0(αmiddotc) asymp 2418 884 254 times 10minus17
s
Callippic cycle equiv 441 mo (hollow) + 499 mo (full) = 76 a of 36525 d = 2398 3776 times 109 s
century c equiv 100 a (see below for definition of year length) = 100 times year
day d = 24 h = 86400 s
day (sidereal) d equiv Time needed for the Earth to rotate once around its axisdetermined from successive transits of a very distantastronomical object across an observers meridian(International Celestial Reference Frame)
asymp 86 1641 s
decade dec equiv 10 a (see below for definition of year length) = 10 times year
fortnight fn equiv 2 wk = 1 209 600 s
helek equiv 11 080 h = 33 s
Hipparchic cycle equiv 4 Callippic cycles - 1 d = 9593 424 times 109 s
hour h equiv 60 min = 3 600 s
jiffy j equiv 160 s = 016 s
jiffy (alternate) ja equiv 1100 s = 10 ms
ke (quarter of an hour) equiv frac14 h = 196 d = 60 times 60 4 s = 900 s= 60 4 min = 15 min
Conversion of units 13
ke (traditional) equiv 1100 d = 24 times 60 times 60 100 s =864 s = 24 60 100min = 144 min
lustre lustrum equiv 5 a of 365 d = 15768 times 108 s
Metonic cycle enneadecaeteris equiv 110 mo (hollow) + 125 mo (full) = 6940 d asymp 19 a = 5996 16 times 108 s
millennium equiv 1 000 a (see below for definition of year length) = 1000 times year
milliday md equiv 11 000 d = 24 times 60 times 60 1 000 s= 864 s
minute min equiv 60 s due to leap seconds sometimes 59 s or 61 s = 60 s
moment equiv 90 s = 90 s
month (full) mo equiv 30 d[20] = 2 592 000 s
month (Greg av) mo Average Gregorian month = 365242512 d = 30436875 d asymp 26297 times 106 s
month (hollow) mo equiv 29 d[20] = 2 505 600 s
month (synodic) mo Cycle time of moon phases asymp 29530589 days (Average) asymp 2551 times 106 s
octaeteris = 48 mo (full) + 48 mo (hollow) + 3 mo (full)[21] [22] = 8 aof 36525 d = 2922 d
= 2524 608 times 108 s
Planck time equiv (Gℏc5)frac12 asymp 1351 211 868 times 10minus43
s
second s time of 9 192 631 770 periods of the radiation correspondingto the transition between the 2 hyperfine levels of the groundstate of the caesium 133 atom at 0 K[8] (but other secondsare sometimes used in astronomy)
(SI base unit)
shake equiv 10minus8 s = 10 ns
sigma equiv 10minus6 s = 1 μs
Sothic cycle equiv 1 461 a of 365 d = 4607 4096 times 1010 s
svedberg S equiv 10minus13 s = 100 fs
week wk equiv 7 d = 604 800 s
year (Gregorian) a y oryr
= 3652425 d average calculated from common years (365d) plus leap years (366 d) on most years divisible by 4 Seeleap year for details
= 31 556 952 s
year (Julian) a y oryr
= 36525 d average calculated from common years (365 d)plus one leap year (366 d) every four years
= 31 557 600 s
year (sidereal) a y oryr
equiv time taken for Sun to return to the same position withrespect to the stars of the celestial sphere
asymp 365256 363 d asymp 31558 1497632 s
year (tropical) a y oryr
equiv Length of time it takes for the Sun to return to the sameposition in the cycle of seasons
asymp 365242 190 d asymp 31556 925 s
Where UTC is observed the length of timeunits longer than 1 s may increase or decreaseby 1 s if a leap second occurs during the timeinterval of interest
Conversion of units 14
Frequency
Frequency
Name of unit Symbol Definition Relation to SI units
hertz (SI unit) Hz equiv Number of cycles per second = 1 Hz = 1s
revolutions per minute rpm equiv One unit rpm equals one rotation completed around a fixed axis in one minute of time asymp0104719755 rads
Speed or velocity
Speed
Name of unit Symbol Definition Relation to SI units
foot per hour fph equiv 1 fth asymp 8466 667 times 10minus5
ms
foot per minute fpm equiv 1 ftmin = 508 times 10minus3 ms
foot per second fps equiv 1 fts = 3048 times 10minus1 ms
furlong perfortnight
equiv furlongfortnight asymp 1663 095 times 10minus4
ms
inch per minute ipm equiv 1 inmin asymp 423 333 times 10minus4 ms
inch per second ips equiv 1 ins = 254 times 10minus2 ms
mach number M Ratio of the speed to the speed of sound in the medium Varies especially with temperatureAbout 761 mph (1225 kph) in air at sea level to about 660 mph (1062 kph) at jet altitudesUnitless
asymp 340 to 295 ms foraircraft
metre per second(SI unit)
ms equiv 1 ms = 1 ms
mile per hour mph equiv 1 mih = 0447 04 ms
mile per minute mpm equiv 1 mimin = 268224 ms
mile per second mps equiv 1 mis = 1 609344 ms
speed of light invacuum
c equiv 299 792 458 ms = 299 792 458 ms
speed of sound inair
s Varies especially with temperature About 761 mph (1225 kph) in air at sea level to about660 mph (1062 kph) at jet altitudes
asymp 340 to 295 ms ataircraft altitudes
A velocity consists of a speed combined with a direction the speed part of the velocity takes units of speed
Conversion of units 15
Flow (volume)
Flow
Name of unit Symbol Definition Relation to SI units
cubic foot per minute CFM equiv 1 ft3min = 4719474432 times 10minus4 m3s
cubic foot per second ft3s equiv 1 ft3s = 0028316846592 m3s
cubic inch per minute in3min equiv 1 in3min = 27311773 times 10minus7 m3s
cubic inch per second in3s equiv 1 in3s = 16387064 times 10minus5 m3s
cubic metre per second (SIunit)
m3s equiv 1 m3s = 1 m3s
gallon (US fluid) per day GPD equiv 1 gald = 4381263638 times 10minus8 m3s
gallon (US fluid) per hour GPH equiv 1 galh = 1051503273 times 10minus6 m3s
gallon (US fluid) per minute GPM equiv 1 galmin = 630901964 times 10minus5 m3s
litre per minute LPM equiv 1 Lmin = 16 times 10minus5 m3s
Acceleration
Acceleration
Name of unit Symbol Definition Relation to SI units
foot per hour per second fphs equiv 1 ft(hmiddots) asymp 8466 667 times 10minus5
ms2
foot per minute per second fpms equiv 1 ft(minmiddots) = 508 times 10minus3 ms2
foot per second squared fps2 equiv 1 fts2 = 3048 times 10minus1 ms2
gal galileo Gal equiv 1 cms2 = 10minus2 ms2
inch per minute per second ipms equiv 1 in(minmiddots) asymp 4233 333 times 10minus4
ms2
inch per second squared ips2 equiv 1 ins2 = 254 times 10minus2 ms2
knot per second kns equiv 1 kns asymp 5144 444 times 10minus1
ms2
metre per second squared (SI unit) ms2 equiv 1 ms2 = 1 ms2
mile per hour per second mphs equiv 1 mi(hmiddots) = 44704 times 10minus1 ms2
mile per minute per second mpms equiv 1 mi(minmiddots) = 268224 ms2
mile per second squared mps2 equiv 1 mis2 = 1609 344 times 103 ms2
standard gravity g equiv 9806 65 ms2 = 9806 65 ms2
Conversion of units 16
Force
Force
Name of unit Symbol Definition Relation to SI units
atomic unit of force equiv memiddotα2middotc2a0 asymp 8238 722 06 times 10minus8 N
[23]
dyne (cgs unit) dyn equiv gmiddotcms2 = 10minus5 N
kilogram-force kilopondgrave-force
kgf kp Gf equiv g times 1 kg = 9806 65 N
kip kip-force kip kipfklbf
equiv g times 1 000 lb = 4448 221 6152605 times 103 N
milligrave-force gravet-force mGf gf equiv g times 1 g = 9806 65 mN
newton (SI unit) N A force capable of giving a mass of one kg an acceleration of one metreper second per second[24]
= 1 N = 1 kgmiddotms2
ounce-force ozf equiv g times 1 oz = 0278 013 850 9537812 N
pound lb equiv slugmiddotfts2 = 4448 230 531 N
pound-force lbf equiv g times 1 lb = 4448 221 615 2605 N
poise (cgs unit) P equiv 10minus1 Pamiddots = 01 Pamiddots
pound per foot hour lb(ftmiddoth) equiv 1 lb(ftmiddoth) asymp 4133 789 times 10minus4 Pamiddots
pound per foot second lb(ftmiddots) equiv 1 lb(ftmiddots) asymp 1488164 Pamiddots
pound-force second per square foot lbfmiddotsft2 equiv 1 lbfmiddotsft2 asymp 4788026 Pamiddots
pound-force second per square inch lbfmiddotsin2 equiv 1 lbfmiddotsin2 asymp 6894757 Pamiddots
Conversion of units 21
Kinematic viscosity
Kinematic viscosity
Name of unit Symbol Definition Relation to SI units
square foot per second ft2s equiv 1 ft2s = 009290304 m2s
square metre per second (SI unit) m2s equiv 1 m2s = 1 m2s
stokes (cgs unit) St equiv10minus4 m2s
= 10minus4 m2s
Electric current
Electric current
Name of unit Symbol Definition Relation to SI units
ampere (SI base unit) A equiv The constant current needed to produce a force of 2 times 10minus7 newton per metre betweentwo straight parallel conductors of infinite length and negligible circular cross-sectionplaced one metre apart in a vacuum[8]
= 1 A
electromagnetic unitabampere (cgs unit)
abamp equiv 10 A = 10 A
esu per secondstatampere (cgs unit)
esus equiv (01 Amiddotms) c asymp3335641 times 10minus10 A
Electric charge
Electric charge
Name of unit Symbol Definition Relation to SI units
abcoulomb electromagnetic unit (cgsunit)
abC emu equiv 10 C = 10 C
atomic unit of charge au equiv e asymp 1602 176462 times 10minus19 C
coulomb (SI unit) C equiv The amount of electricity carried in one second of time by oneampere of current[24]
= 1 C = 1 Amiddots
faraday F equiv 1 mol times NAmiddote asymp 96 4853383 C
statcoulomb franklin electrostatic unit(cgs unit)
statC Fresu
equiv (01 Amiddotm) c asymp 3335 641 times 10minus10 C
Conversion of units 22
Electric dipole
Electric dipole
Name of unit Symbol Definition Relation to SI units
atomic unit of electric dipole moment ea0 asymp 8478 352 81 times 10minus30
Cmiddotm[28]
Electromotive force electric potential difference
Voltage electromotive force
Name ofunit
Symbol Definition Relation to SI units
abvolt (cgsunit)
abV equiv 1 times 10minus8 V = 1 times 10minus8 V
statvolt (cgsunit)
statV equiv cmiddot (1 μJAmiddotm) = 299792 458 V
volt (SIunit)
V The difference in electric potential across two points along a conducting wire carrying one ampereof constant current when the power dissipated between the points equals one watt[24]
= 1 V = 1 WA = 1kgmiddotm2(Amiddots3)
Electrical resistance
Electrical resistance
Name ofunit
Symbol Definition Relation to SI units
ohm (SIunit)
Ω The resistance between two points in a conductor when one volt of electric potential differenceapplied to these points produces one ampere of current in the conductor[24]
= 1 Ω = 1 VA = 1kgmiddotm2(A2middots3)
Capacitance
Capacitors ability to store charge
Name ofunit
Symbol Definition Relation to SI units
farad (SIunit)
F The capacitance between two parallel plates that results in one volt of potential difference whencharged by one coulomb of electricity[24]
= 1 F = 1 CV = 1A2middots4(kgmiddotm2)
Conversion of units 23
Magnetic flux
magnetic flux
Name of unit Symbol Definition Relation to SI units
maxwell (CGSunit)
Mx equiv 10minus8 Wb[29] = 1 times 10minus8 Wb
weber (SIunit)
Wb Magnetic flux which linking a circuit of one turn would produce in it an electromotive force of1 volt if it were reduced to zero at a uniform rate in 1 second[24]
= 1 Wb = 1 Vmiddots = 1kgmiddotm2(Amiddots2)
Magnetic flux density
What physicists call Magnetic field is called Magnetic flux density by electrical engineersand magnetic induction by applied mathematicians and electrical engineers
Name of unit Symbol Definition Relation to SI units
gauss (CGS unit) G equiv Mxcm2 = 10minus4
T= 1 times 10minus4 T [30]
tesla (SI unit) T equiv Wbm2 = 1 T = 1 Wbm2 = 1kg(Amiddots2)
Inductance
Inductance
Name ofunit
Symbol Definition Relation to SI units
henry (SIunit)
H The inductance of a closed circuit that produces one volt of electromotive force when the current inthe circuit varies at a uniform rate of one ampere per second[24]
= 1 H = 1 WbA = 1kgmiddotm2(Amiddots)2
Temperature
Temperature
Name of unit Symbol Definition Conversion to kelvin
degree Celsius degC degC equiv K minus 27315 [K] equiv [degC] + 27315
degree Delisle degDe [K] = 37315 minus [degDe] times 23
degree Fahrenheit degF degF equiv degC times 95 + 32 [K] equiv ([degF] + 45967) times 59
degree Newton degN [K] = [degN] times 10033 + 27315
degree Rankine degR degRa degR equiv K times 95 [K] equiv [degR] times 59
degree Reacuteaumur degReacute [K] = [degReacute] times 54 + 27315
degree Roslashmer degRoslash [K] = ([degRoslash] minus 75) times 4021 + 27315
kelvin (SI baseunit)
K equiv 127316 of the thermodynamic temperature of the triple point of water[8] equiv 1 K
Conversion of units 24
Information entropy
Information entropy
Name of unit Symbol Definition Relation to SI units Relation to bits
SI unit JK equiv JK = 1 JK
nat nip nepit nat equiv kB = 1380 650 5(23) times 10minus23 JK
bit shannon bit b Sh equiv ln(2) times kB = 9569 940 (16) times 10minus24 JK = 1 bit
ban hartley ban Hart equiv ln(10) times kB = 3179 065 3(53) times 10minus23 JK
nibble equiv 4 bits = 3827 976 0(64) times 10minus23 JK = 22 bit
byte B equiv 8 bits = 7655 952 (13) times 10minus23 JK = 23 bit
kilobyte (decimal) kB equiv 1 000 B = 7655 952 (13) times 10minus20 JK
kilobyte (kibibyte) KB KiB equiv 1 024 B = 7839 695 (13) times 10minus20 JK = 210 bit
Often information entropy is measured in shannons whereas the (discrete) storage space of digital devices ismeasured in bits Thus uncompressed redundant data occupy more than one bit of storage per shannon ofinformation entropy The multiples of a bit listed above are usually used with this meaning Other times the bit isused as a measure of information entropy and is thus a synonym of shannon
Luminous intensityThe candela is the preferred nomenclature for the SI unit
Luminous intensity
Name of unit Symbol Definition Relation toSI units
candela (SI baseunit) candle
cd The luminous intensity in a given direction of a source that emits monochromatic radiation offrequency 540 times 1012 hertz and that has a radiant intensity in that direction of 1683 watt persteradian[8]
= 1 cd
candlepower (new) cp equiv cd The use of candlepower as a unit is discouraged due to its ambiguity = 1 cd
candlepower (oldpre-1948)
cp Varies and is poorly reproducible[31] Approximately 0981 cd[14] asymp 0981 cd
Luminance
Conversion of units 25
Luminance
Name of unit Symbol Definition Relation to SI units
candela per square foot cdft2 equiv cdft2 asymp10763910417 cdm2
candela per square inch cdin2 equiv cdin2 asymp 15500031 cdm2
candela per square metre (SI unit) nit (deprecated[14] ) cdm2 equiv cdm2 = 1 cdm2
Name of unit Symbol Definition Relation to SI units
lumen (SIunit)
lm equiv cdmiddotsr = 1 lm = 1 cdmiddotsr
Illuminance
Illuminance
Name of unit Symbol Definition Relation to SI units
footcandle lumen per square foot fc equiv lmft2 = 10763910417 lx
lumen per square inch lmin2 equiv lmin2 asymp 15500031 lx
lux (SI unit) lx equiv lmm2 = 1 lx = 1 lmm2
phot (CGS unit) ph equiv lmcm2 = 1 times 104 lx
Radiation - source activity
Conversion of units 26
Radioactivity
Name of unit Symbol Definition Relation to SI units
becquerel (SIunit)
Bq equiv Number of disintegrations per second = 1 Bq = 1s
curie Ci equiv 37 times 1010 Bq = 37 times 1010 Bq [32]
rutherford (H) rd equiv 1 MBq = 1 times 106 Bq
Please note that although becquerel (Bq) and hertz (Hz) both ultimately refer to the same SI base unit (sminus1) Hz isused only for periodic phenomena and Bq is only used for stochastic processes associated with radioactivity[33]
Radiation - exposure
Radiation - exposure
Name of unit Symbol Definition Relation to SI units
roentgen R 1 R equiv 258 times 10minus4 Ckg[29] = 258 times 10minus4 Ckg
The roentgen is not a SI unit and the NIST strongly discourages its continued use[34]
Radiation - absorbed dose
Radiation - absorbed dose
Name of unit Symbol Definition Relation to SI units
Name of unit Symbol Definition Relation to SI units
Roumlntgen equivalent man rem equiv 001 Sv = 001 Sv
sievert (SI unit) Sv equiv 1 Jkg[33] = 1 Sv
Although the definitions for sievert (Sv) and gray (Gy) would seem to indicate that they measure the same quantitiesthis is not the case The effect of receiving a certain dose of radiation (given as Gy) is variable and depends on manyfactors thus a new unit was needed to denote the biological effectiveness of that dose on the body this is known asthe equivalent dose and is shown in Sv The general relationship between absorbed dose and equivalent dose can berepresented as
H = Q middot D
where H is the equivalent dose D is the absorbed dose and Q is a dimensionless quality factor Thus for anyquantity of D measured in Gy the numerical value for H measured in Sv may be different[36]
Conversion of units 27
Software toolsHome and office computers come with converters in bundled spreadsheet applications or can access free convertersvia the Internet Units and measurements can be easily converted using these tools but only if the units are explicitlydefined and the conversion is compatible (eg cmHg to kPa)
Free conversion softwarebull Units (software) a popular cross-platform command-line utilitybull Converter [37] contextual unit converter for Mozilla Firefox browsersbull Converber [38] portable application converting utilitybull calculla [39] calculla - online web convertersbull iMetrix [40] - unit converter for xpbull uniteasy [41] online scientific unit conversionbull Unit Converter Add-in for Excel [42] - allow a large selection of unit conversions within the Microsoft Excel
spread sheet programbull Unit Converter [43] simple and extensible unit converterbull Portable Unit Converter [44] including 4500 units 33 unit-categories and the possibility to create custom units
General commercial sources of convertersbull Advanced electronic calculators have unit-conversion functionalitybull Spreadsheet programs usually provide conversion functions or formulas or the user can write their ownbull Commercial mathematical scientific and technical applications often include converters
See also
bull Accuracy and precisionbull English unitsbull False precisionbull Imperial unitsbull International System of Unitsbull Mesures usuellesbull Metric system
bull Natural unitsbull Roundingbull Significant figuresbull Temperature conversionbull United States customary unitsbull Units conversion by factor-labelbull Units of measurement
External linksbull British law Units of measurement regulations 1995 [45]
bull ConvertBuster [46] Variety of conversion tools to convert easilybull How Many A dictionary of units of measurement [47]
bull NIST Fundamental physical constants mdash Non-SI units [48]PDF (357 KB)bull NIST Guide to SI Units [49] Many conversion factors listedbull Online Conversion Calculators [50] Very extensive list of conversions from-to equvalent unitsbull The Unified Code for Units of Measure [51]
bull Units Symbols and Conversions XML Dictionary [52]
bull Multilingual Online Conversion of Units [53]
bull Temperature Converter [54]
Conversion of units 28
References[1] United States Naval Observatory (2009) Selected Astronomical Constants 2009 (http asa usno navy mil SecK 2009
Astronomical_Constants_2009 txt) Accessed May 10 2009[2] NIST Reference on Constants Units and Uncertainty (http physics nist gov cgi-bin cuu Valuebohrrada0|search_for=Bohr+
radius)(2006) National Institute of Standards and Technology Retrieved February 22 2008[3] National Institute of Standards and Technology General Tables of Units of Measurement (http ts nist gov WeightsAndMeasures
Publications appxc cfm)[4] Lide D (Ed) (1990) Handbook of Chemistry and Physics (71st ed) Boca Raton FL CRC Press Section 1[5] National Bureau of Standards (June 30 1959) Refinement of values for the yard and the pound Federal Register viewed September 20
2006 at National Geodetic Survey web site (http www ngs noaa gov PUBS_LIB FedRegister FRdoc59-5442 pdf)[6] The International Astronomical Union and Astronomical Units (http www iau org public_press themes measuring )[7] Klein Herbert Arthur (1988) The Science of Measurement a Historical Survey Mineola NY Dover Publications 0-4862-5839-4[8] The International System of Units Section 21 (http www bipm org en si si_brochure chapter2 2-1 ) (8 ed) Bureau International des
Poids et Mesures 2006 retrieved August 26 2009[9] International System of Units (http www bipm org en si si_brochure chapter4 table8 html) 8th ed (2006) Bureau International des
Poids et Mesures Section 41 Table 8[10] P Kenneth Seidelmann Ed (1992) Explanatory Supplement to the Astronomical Almanac Sausalito CA University Science Books p 716
and sv parsec in Glossary[11] Whitelaw Ian (2007) A Measure of All Things The Story of Man and Measurement (http books google com
booksid=3zgGEWM5-iAC) New York Macmillan 0-312-37026-1 p 152[12] De Vinne Theodore Low (1900) The practice of typography a treatise on the processes of type-making the point system the names sizes
styles and prices of plain printing types (http books google com booksid=R4-DjphIpLMC) 2nd ed New York The Century Co p142ndash150
[13] Pasko Wesley Washington (1894) American dictionary of printing and bookmaking (http books google combooksid=Z_QUAAAAIAAJ) (1894) New York Howard Lockwood p 521
[14] Rowlett Russ (2005) How Many A Dictionary of Units of Measurement (http www unc edu ~rowlett units index html)[15] Thompson A and Taylor BN (2008) Guide for the Use of the International System of Units (SI) National Institute of Standards and
Technology Special Publication 811 p 57[16] US Code of Federal Regulations Title 21 Section 1019 Paragraph (b)(5)(viii) (http ecfr gpoaccess gov cgi t text text-idxc=ecframp
rgn=div8amp view=textamp node=212 0 1 1 2 1 1 6amp idno=21) retrieved August 29 2009[17] Barry N Taylor Ed NIST Special Publication 330 The International System of Units (SI) (http physics nist gov Pubs SP330 sp330
pdf) (2001 Edition) Washington US Government Printing Office 43The 12th Conference Generale des Poids et Mesures(CGPM)hellipdeclares that the word ldquolitrerdquo may be employed as a special name for the cubic decimetre
[18] CODATA Value atomic uint of mass (http physics nist gov cgi-bin cuu Valuettme|search_for=atomic+ unit+ of+ mass) (2006)National Institute of Standards and Technology Retrieved 16 September 2008
[19] The Swiss Federal Office for Metrology gives Zentner on a German language web page (http www metas ch de scales systemch html)and quintal on the English translation of that page (http www metas ch en scales systemch html) the unit is marked speacutecifiquementsuisse
[20] Pedersen O (1983) Glossary in Coyne G Hoskin M and Pedersen O Gregorian Reform of the Calendar Proceedings of the VaticanConference to Commemorate its 400th Anniversary Vatican Observatory Available from Astrophysics Data System
[21] Richards EG (1998) Mapping Time Oxford University Press pp 94ndash95 ISBN 0-19-850413-6[22] Steel Duncan (2000) Marking Time John Wiley amp Sons p 46 ISBN 0-471-29827-1[23] CODATA Value atomic unit of force (http physics nist gov cuu Constants ) (2006) National Institute of Standards and Technology
Retrieved September 14 2008[24] [[Comiteacute International des Poids et Mesures (http www bipm org en CIPM db 1946 2 )] Resolution 2] 1946 retrieved August 26
2009[25] Barry N Taylor (April 1995) Guide for the Use of the International System of Units (SI) (http physics nist gov cuu pdf sp811 pdf)
(NIST Special Publication 811) Washington DC US Government Printing Office pp 57ndash68[26] Barry N Taylor (April 1995) Guide for the Use of the International System of Units (SI) (NIST Special Publication 811) Washington DC
US Government Printing Office p 5[27] International System of Units (http www bipm org en si si_brochure chapter4 table7 html) 8th ed (2006) Bureau International des
Poids et Mesures Section 41 Table 7[28] The NIST Reference on Constants Units and Uncertainty (http physics nist gov cgi-bin cuu Valueauedm) 2006 retrieved August
26 2009[29] NIST Guide to SI Units Appendix B9 (http physics nist gov Pubs SP811 appenB9 html) retrieved August 27 2009[30] Standard for the Use of the International System of Units (SI) The Modern Metric System IEEEASTM SI 10-1997 (1997) New York and
West Conshohocken PA Institute of Electrical and Electronics Engineers and American Society for Testing and Materials Tables A1through A5
Conversion of units 29
[31] The NIST Reference on Constants Units and Uncertainty (http physics nist gov cuu Units candela html) retrieved August 28 2009[32] Ambler Thompson amp Barry N Taylor (2008) Guide for the Use of the International System of Units (SI) (http physics nist gov cuu
pdf sp811 pdf) Special Publication 811 Gaithersburg MD National Institute of Standards and Technology p 10[33] The International System of Units Section 222 Table 3 (http www bipm org en si si_brochure chapter2 2-2 table3 html) (8 ed)
Bureau International des Poids et Mesures 2006 retrieved August 27 2009[34] The NIST Guide to the SI (Special Publication 811) section 52 (http physics nist gov Pubs SP811 sec05 html5 2) 2008 retrieved
August 27 2009[35] Ambler Thompson amp Barry N Taylor (2008) Guide for the Use of the International System of Units (SI) (http physics nist gov cuu
pdf sp811 pdf) Special Publication 811 Gaithersburg MD National Institute of Standards and Technology p 5[36] [[Comiteacute international des poids et mesures (http www bipm org en CIPM db 2002 2 )] 2002 Recommendation 2] retrieved
August 27 2009[37] http converter mozdev org[38] http www xyntec com converber htm[39] http www calculla com[40] http illusions hu index phptask=100amp lang=0amp statpage=86[41] http www uniteasy com[42] http www tenderwire com wikipedialandingpage[43] http www kamlex com index phpoption=com_contentamp view=articleamp id=53amp Itemid=55[44] http www sttmedia com unitconverter[45] http www hmso gov uk si si1995 Uksi_19951804_en_2 htm[46] http www convertbuster com[47] http www unc edu ~rowlett units[48] http physics nist gov cuu Document nonsi_in_1998 pdf[49] http physics nist gov Pubs SP811 appenB9 html[50] http www onlineconversion com[51] http aurora rg iupui edu ~schadow units UCUM ucum html[52] http www posc org refs poscUnits20 xml[53] http www imperialtometric com[54] http www tampile com
Article Sources and Contributors 30
Article Sources and ContributorsConversion of units Source httpenwikipediaorgwindexphpoldid=373975089 Contributors 1571781xxx 7 A-giau AVSI Acather96 Ahoerstemeier Alexius08 Altenmann AndreEngels Andrewa Andy120290 Anonymi Ariconte Army1987 ArnoldReinhold Arthur3030 Aspects AxelBoldt AzaToth Azikala BW95 Bdesham Beland Bensaccount Bkumartvm Blackand White BlaiseFEgan BlueEarth Bobblewik Borbrav Bpmullins Bryan Derksen C J B Scholten CORNELIUSSEON CTZMSC3 Calltech Camerajohn Chaosfeary Charles MatthewsChris the speller Cmdrjameson Colonies Chris Conversion script Cope555 Crappy13 Crissov CyrilB DARTH SIDIOUS 2 DMacks DanielCD Dark Formal DarkestSideX DekisugiDenelson83 Dhp1080 Dicklyon DirkvdM Donald Duck Donarreiskoffer Dramatic Dyss DAringsbquougosz Egil Ehrenkater Ejohnsonboulder Elexmax Elf Emokhberi Enon Eob Epbr123Euchiasmus Fathead99 Father Goose Fella22 Femto FernandoAC Fibula Flutefreek Fred Bauder Fredrik Fuhghettaboutit Fuzheado Gaff Gene Nygaard Georgiy1996 Gerry AshtonGiftlite Gilliam Glenn L GoingBatty Goobergunch Gregsexton Greyengine5 Grunt Gurch Gutza HLHJ Haemo Hammersbach Heracles31 Herbee Heron HikerBush Hqb IcairnsIgiffin Indefatigable Isis JBobbitt JHunterJ Jabowery JakeVortex Jamicanmonkey Jason Begin Jay Jc3s5h Jcronen1 Jdoherty Jeffz1 Jeronimo Jimmuhk Jimp Jimwilliams57 JoeinwapJohndburger Josh Parris Jq4bagiq Kaihsu KaneWang Keenan Pepper Kevin Rector KeyStorm Khukri Kurtan Lee Daniel Crocker LightYear Linuxoidoz Liv4christ210 Loggie Lolo252Lupinelawyer M ichaeligl MJCdetroit MTC Mac MacMcF Magore Markus Kuhn Masterqwe MaxHund Maxamegalon2000 Mbeychok Meggar Mh26 Michael Daly Michael Hardy MichelAudy Mikelifeguard Mikhailov Kusserow Mindbuilder Missvain Monger Mr bulow MrOllie MrZhuKeeper Muro de Aguas Mwanner Mwtoews Nandesuka Natkeeran Ndsg NgjaimeNhy67ygv Nick Y Nick123 NickPenguin Ninjagecko Noe Nosilleg Now3r3 Obelix homologator Oldadamml Oleg Alexandrov Olivier Ortolan88 OwenBlacker Pac72 PassargeaPatrick Paul Martin Peter Horn Physchim62 Piels Pierdm Pmanderson Prometheus235 Quadell QuantumEleven Quod erat demonstrandum 314159 Radagast83 Rccoms RedWolfReinyday Revipm Rexparry sydney Reyk Rhetth Rhialto Rich Farmbrough Richard Myers Rjwilmsi Rlsheehan Robin Barry RoySmith Rpwolfgram SD6-Agent SGBailey SamuelLowry Samw Sander123 Seabhcan SebastianHelm Sherbert1 Shinhan Shrew Sietse Snel SimonP Sinbaddasail0r Skotte Smalljim SomeHuman Spencer Srleffler StarwarsmastergeekSteacoon StefanK SteveRamone Stevertigo Stokerm Suisui Sunev Superboy112233 Superm401 Synchronism Tacoman1996 Tarquin Taw Teratornis The Man in Question ThierrycThingg Thinking of England Thunderbird2 Timwi Tobias Hoevekamp Tomasr Tonsofpcs Toon05 Topsykretts2512 Trekphiler Tuwile Twanvl Uday147502 Unitman00 UrhixidurUtherSRG Vargenau Vsmith WarrenPlatts Wasell Welsh Whispering Wikinger Wolfkeeper Wtmitchell XJamRastafire Xenonice Yath Zginder Zibem Zocky Zotel 713 anonymousedits
slug per cubic foot slugft3 equiv slugft3 asymp 5153788184 kgm3
Time
Time t
Name of unit Symbol Definition Relation to SI units
atomic unit of time au equiv a0(αmiddotc) asymp 2418 884 254 times 10minus17
s
Callippic cycle equiv 441 mo (hollow) + 499 mo (full) = 76 a of 36525 d = 2398 3776 times 109 s
century c equiv 100 a (see below for definition of year length) = 100 times year
day d = 24 h = 86400 s
day (sidereal) d equiv Time needed for the Earth to rotate once around its axisdetermined from successive transits of a very distantastronomical object across an observers meridian(International Celestial Reference Frame)
asymp 86 1641 s
decade dec equiv 10 a (see below for definition of year length) = 10 times year
fortnight fn equiv 2 wk = 1 209 600 s
helek equiv 11 080 h = 33 s
Hipparchic cycle equiv 4 Callippic cycles - 1 d = 9593 424 times 109 s
hour h equiv 60 min = 3 600 s
jiffy j equiv 160 s = 016 s
jiffy (alternate) ja equiv 1100 s = 10 ms
ke (quarter of an hour) equiv frac14 h = 196 d = 60 times 60 4 s = 900 s= 60 4 min = 15 min
Conversion of units 13
ke (traditional) equiv 1100 d = 24 times 60 times 60 100 s =864 s = 24 60 100min = 144 min
lustre lustrum equiv 5 a of 365 d = 15768 times 108 s
Metonic cycle enneadecaeteris equiv 110 mo (hollow) + 125 mo (full) = 6940 d asymp 19 a = 5996 16 times 108 s
millennium equiv 1 000 a (see below for definition of year length) = 1000 times year
milliday md equiv 11 000 d = 24 times 60 times 60 1 000 s= 864 s
minute min equiv 60 s due to leap seconds sometimes 59 s or 61 s = 60 s
moment equiv 90 s = 90 s
month (full) mo equiv 30 d[20] = 2 592 000 s
month (Greg av) mo Average Gregorian month = 365242512 d = 30436875 d asymp 26297 times 106 s
month (hollow) mo equiv 29 d[20] = 2 505 600 s
month (synodic) mo Cycle time of moon phases asymp 29530589 days (Average) asymp 2551 times 106 s
octaeteris = 48 mo (full) + 48 mo (hollow) + 3 mo (full)[21] [22] = 8 aof 36525 d = 2922 d
= 2524 608 times 108 s
Planck time equiv (Gℏc5)frac12 asymp 1351 211 868 times 10minus43
s
second s time of 9 192 631 770 periods of the radiation correspondingto the transition between the 2 hyperfine levels of the groundstate of the caesium 133 atom at 0 K[8] (but other secondsare sometimes used in astronomy)
(SI base unit)
shake equiv 10minus8 s = 10 ns
sigma equiv 10minus6 s = 1 μs
Sothic cycle equiv 1 461 a of 365 d = 4607 4096 times 1010 s
svedberg S equiv 10minus13 s = 100 fs
week wk equiv 7 d = 604 800 s
year (Gregorian) a y oryr
= 3652425 d average calculated from common years (365d) plus leap years (366 d) on most years divisible by 4 Seeleap year for details
= 31 556 952 s
year (Julian) a y oryr
= 36525 d average calculated from common years (365 d)plus one leap year (366 d) every four years
= 31 557 600 s
year (sidereal) a y oryr
equiv time taken for Sun to return to the same position withrespect to the stars of the celestial sphere
asymp 365256 363 d asymp 31558 1497632 s
year (tropical) a y oryr
equiv Length of time it takes for the Sun to return to the sameposition in the cycle of seasons
asymp 365242 190 d asymp 31556 925 s
Where UTC is observed the length of timeunits longer than 1 s may increase or decreaseby 1 s if a leap second occurs during the timeinterval of interest
Conversion of units 14
Frequency
Frequency
Name of unit Symbol Definition Relation to SI units
hertz (SI unit) Hz equiv Number of cycles per second = 1 Hz = 1s
revolutions per minute rpm equiv One unit rpm equals one rotation completed around a fixed axis in one minute of time asymp0104719755 rads
Speed or velocity
Speed
Name of unit Symbol Definition Relation to SI units
foot per hour fph equiv 1 fth asymp 8466 667 times 10minus5
ms
foot per minute fpm equiv 1 ftmin = 508 times 10minus3 ms
foot per second fps equiv 1 fts = 3048 times 10minus1 ms
furlong perfortnight
equiv furlongfortnight asymp 1663 095 times 10minus4
ms
inch per minute ipm equiv 1 inmin asymp 423 333 times 10minus4 ms
inch per second ips equiv 1 ins = 254 times 10minus2 ms
mach number M Ratio of the speed to the speed of sound in the medium Varies especially with temperatureAbout 761 mph (1225 kph) in air at sea level to about 660 mph (1062 kph) at jet altitudesUnitless
asymp 340 to 295 ms foraircraft
metre per second(SI unit)
ms equiv 1 ms = 1 ms
mile per hour mph equiv 1 mih = 0447 04 ms
mile per minute mpm equiv 1 mimin = 268224 ms
mile per second mps equiv 1 mis = 1 609344 ms
speed of light invacuum
c equiv 299 792 458 ms = 299 792 458 ms
speed of sound inair
s Varies especially with temperature About 761 mph (1225 kph) in air at sea level to about660 mph (1062 kph) at jet altitudes
asymp 340 to 295 ms ataircraft altitudes
A velocity consists of a speed combined with a direction the speed part of the velocity takes units of speed
Conversion of units 15
Flow (volume)
Flow
Name of unit Symbol Definition Relation to SI units
cubic foot per minute CFM equiv 1 ft3min = 4719474432 times 10minus4 m3s
cubic foot per second ft3s equiv 1 ft3s = 0028316846592 m3s
cubic inch per minute in3min equiv 1 in3min = 27311773 times 10minus7 m3s
cubic inch per second in3s equiv 1 in3s = 16387064 times 10minus5 m3s
cubic metre per second (SIunit)
m3s equiv 1 m3s = 1 m3s
gallon (US fluid) per day GPD equiv 1 gald = 4381263638 times 10minus8 m3s
gallon (US fluid) per hour GPH equiv 1 galh = 1051503273 times 10minus6 m3s
gallon (US fluid) per minute GPM equiv 1 galmin = 630901964 times 10minus5 m3s
litre per minute LPM equiv 1 Lmin = 16 times 10minus5 m3s
Acceleration
Acceleration
Name of unit Symbol Definition Relation to SI units
foot per hour per second fphs equiv 1 ft(hmiddots) asymp 8466 667 times 10minus5
ms2
foot per minute per second fpms equiv 1 ft(minmiddots) = 508 times 10minus3 ms2
foot per second squared fps2 equiv 1 fts2 = 3048 times 10minus1 ms2
gal galileo Gal equiv 1 cms2 = 10minus2 ms2
inch per minute per second ipms equiv 1 in(minmiddots) asymp 4233 333 times 10minus4
ms2
inch per second squared ips2 equiv 1 ins2 = 254 times 10minus2 ms2
knot per second kns equiv 1 kns asymp 5144 444 times 10minus1
ms2
metre per second squared (SI unit) ms2 equiv 1 ms2 = 1 ms2
mile per hour per second mphs equiv 1 mi(hmiddots) = 44704 times 10minus1 ms2
mile per minute per second mpms equiv 1 mi(minmiddots) = 268224 ms2
mile per second squared mps2 equiv 1 mis2 = 1609 344 times 103 ms2
standard gravity g equiv 9806 65 ms2 = 9806 65 ms2
Conversion of units 16
Force
Force
Name of unit Symbol Definition Relation to SI units
atomic unit of force equiv memiddotα2middotc2a0 asymp 8238 722 06 times 10minus8 N
[23]
dyne (cgs unit) dyn equiv gmiddotcms2 = 10minus5 N
kilogram-force kilopondgrave-force
kgf kp Gf equiv g times 1 kg = 9806 65 N
kip kip-force kip kipfklbf
equiv g times 1 000 lb = 4448 221 6152605 times 103 N
milligrave-force gravet-force mGf gf equiv g times 1 g = 9806 65 mN
newton (SI unit) N A force capable of giving a mass of one kg an acceleration of one metreper second per second[24]
= 1 N = 1 kgmiddotms2
ounce-force ozf equiv g times 1 oz = 0278 013 850 9537812 N
pound lb equiv slugmiddotfts2 = 4448 230 531 N
pound-force lbf equiv g times 1 lb = 4448 221 615 2605 N
poise (cgs unit) P equiv 10minus1 Pamiddots = 01 Pamiddots
pound per foot hour lb(ftmiddoth) equiv 1 lb(ftmiddoth) asymp 4133 789 times 10minus4 Pamiddots
pound per foot second lb(ftmiddots) equiv 1 lb(ftmiddots) asymp 1488164 Pamiddots
pound-force second per square foot lbfmiddotsft2 equiv 1 lbfmiddotsft2 asymp 4788026 Pamiddots
pound-force second per square inch lbfmiddotsin2 equiv 1 lbfmiddotsin2 asymp 6894757 Pamiddots
Conversion of units 21
Kinematic viscosity
Kinematic viscosity
Name of unit Symbol Definition Relation to SI units
square foot per second ft2s equiv 1 ft2s = 009290304 m2s
square metre per second (SI unit) m2s equiv 1 m2s = 1 m2s
stokes (cgs unit) St equiv10minus4 m2s
= 10minus4 m2s
Electric current
Electric current
Name of unit Symbol Definition Relation to SI units
ampere (SI base unit) A equiv The constant current needed to produce a force of 2 times 10minus7 newton per metre betweentwo straight parallel conductors of infinite length and negligible circular cross-sectionplaced one metre apart in a vacuum[8]
= 1 A
electromagnetic unitabampere (cgs unit)
abamp equiv 10 A = 10 A
esu per secondstatampere (cgs unit)
esus equiv (01 Amiddotms) c asymp3335641 times 10minus10 A
Electric charge
Electric charge
Name of unit Symbol Definition Relation to SI units
abcoulomb electromagnetic unit (cgsunit)
abC emu equiv 10 C = 10 C
atomic unit of charge au equiv e asymp 1602 176462 times 10minus19 C
coulomb (SI unit) C equiv The amount of electricity carried in one second of time by oneampere of current[24]
= 1 C = 1 Amiddots
faraday F equiv 1 mol times NAmiddote asymp 96 4853383 C
statcoulomb franklin electrostatic unit(cgs unit)
statC Fresu
equiv (01 Amiddotm) c asymp 3335 641 times 10minus10 C
Conversion of units 22
Electric dipole
Electric dipole
Name of unit Symbol Definition Relation to SI units
atomic unit of electric dipole moment ea0 asymp 8478 352 81 times 10minus30
Cmiddotm[28]
Electromotive force electric potential difference
Voltage electromotive force
Name ofunit
Symbol Definition Relation to SI units
abvolt (cgsunit)
abV equiv 1 times 10minus8 V = 1 times 10minus8 V
statvolt (cgsunit)
statV equiv cmiddot (1 μJAmiddotm) = 299792 458 V
volt (SIunit)
V The difference in electric potential across two points along a conducting wire carrying one ampereof constant current when the power dissipated between the points equals one watt[24]
= 1 V = 1 WA = 1kgmiddotm2(Amiddots3)
Electrical resistance
Electrical resistance
Name ofunit
Symbol Definition Relation to SI units
ohm (SIunit)
Ω The resistance between two points in a conductor when one volt of electric potential differenceapplied to these points produces one ampere of current in the conductor[24]
= 1 Ω = 1 VA = 1kgmiddotm2(A2middots3)
Capacitance
Capacitors ability to store charge
Name ofunit
Symbol Definition Relation to SI units
farad (SIunit)
F The capacitance between two parallel plates that results in one volt of potential difference whencharged by one coulomb of electricity[24]
= 1 F = 1 CV = 1A2middots4(kgmiddotm2)
Conversion of units 23
Magnetic flux
magnetic flux
Name of unit Symbol Definition Relation to SI units
maxwell (CGSunit)
Mx equiv 10minus8 Wb[29] = 1 times 10minus8 Wb
weber (SIunit)
Wb Magnetic flux which linking a circuit of one turn would produce in it an electromotive force of1 volt if it were reduced to zero at a uniform rate in 1 second[24]
= 1 Wb = 1 Vmiddots = 1kgmiddotm2(Amiddots2)
Magnetic flux density
What physicists call Magnetic field is called Magnetic flux density by electrical engineersand magnetic induction by applied mathematicians and electrical engineers
Name of unit Symbol Definition Relation to SI units
gauss (CGS unit) G equiv Mxcm2 = 10minus4
T= 1 times 10minus4 T [30]
tesla (SI unit) T equiv Wbm2 = 1 T = 1 Wbm2 = 1kg(Amiddots2)
Inductance
Inductance
Name ofunit
Symbol Definition Relation to SI units
henry (SIunit)
H The inductance of a closed circuit that produces one volt of electromotive force when the current inthe circuit varies at a uniform rate of one ampere per second[24]
= 1 H = 1 WbA = 1kgmiddotm2(Amiddots)2
Temperature
Temperature
Name of unit Symbol Definition Conversion to kelvin
degree Celsius degC degC equiv K minus 27315 [K] equiv [degC] + 27315
degree Delisle degDe [K] = 37315 minus [degDe] times 23
degree Fahrenheit degF degF equiv degC times 95 + 32 [K] equiv ([degF] + 45967) times 59
degree Newton degN [K] = [degN] times 10033 + 27315
degree Rankine degR degRa degR equiv K times 95 [K] equiv [degR] times 59
degree Reacuteaumur degReacute [K] = [degReacute] times 54 + 27315
degree Roslashmer degRoslash [K] = ([degRoslash] minus 75) times 4021 + 27315
kelvin (SI baseunit)
K equiv 127316 of the thermodynamic temperature of the triple point of water[8] equiv 1 K
Conversion of units 24
Information entropy
Information entropy
Name of unit Symbol Definition Relation to SI units Relation to bits
SI unit JK equiv JK = 1 JK
nat nip nepit nat equiv kB = 1380 650 5(23) times 10minus23 JK
bit shannon bit b Sh equiv ln(2) times kB = 9569 940 (16) times 10minus24 JK = 1 bit
ban hartley ban Hart equiv ln(10) times kB = 3179 065 3(53) times 10minus23 JK
nibble equiv 4 bits = 3827 976 0(64) times 10minus23 JK = 22 bit
byte B equiv 8 bits = 7655 952 (13) times 10minus23 JK = 23 bit
kilobyte (decimal) kB equiv 1 000 B = 7655 952 (13) times 10minus20 JK
kilobyte (kibibyte) KB KiB equiv 1 024 B = 7839 695 (13) times 10minus20 JK = 210 bit
Often information entropy is measured in shannons whereas the (discrete) storage space of digital devices ismeasured in bits Thus uncompressed redundant data occupy more than one bit of storage per shannon ofinformation entropy The multiples of a bit listed above are usually used with this meaning Other times the bit isused as a measure of information entropy and is thus a synonym of shannon
Luminous intensityThe candela is the preferred nomenclature for the SI unit
Luminous intensity
Name of unit Symbol Definition Relation toSI units
candela (SI baseunit) candle
cd The luminous intensity in a given direction of a source that emits monochromatic radiation offrequency 540 times 1012 hertz and that has a radiant intensity in that direction of 1683 watt persteradian[8]
= 1 cd
candlepower (new) cp equiv cd The use of candlepower as a unit is discouraged due to its ambiguity = 1 cd
candlepower (oldpre-1948)
cp Varies and is poorly reproducible[31] Approximately 0981 cd[14] asymp 0981 cd
Luminance
Conversion of units 25
Luminance
Name of unit Symbol Definition Relation to SI units
candela per square foot cdft2 equiv cdft2 asymp10763910417 cdm2
candela per square inch cdin2 equiv cdin2 asymp 15500031 cdm2
candela per square metre (SI unit) nit (deprecated[14] ) cdm2 equiv cdm2 = 1 cdm2
Name of unit Symbol Definition Relation to SI units
lumen (SIunit)
lm equiv cdmiddotsr = 1 lm = 1 cdmiddotsr
Illuminance
Illuminance
Name of unit Symbol Definition Relation to SI units
footcandle lumen per square foot fc equiv lmft2 = 10763910417 lx
lumen per square inch lmin2 equiv lmin2 asymp 15500031 lx
lux (SI unit) lx equiv lmm2 = 1 lx = 1 lmm2
phot (CGS unit) ph equiv lmcm2 = 1 times 104 lx
Radiation - source activity
Conversion of units 26
Radioactivity
Name of unit Symbol Definition Relation to SI units
becquerel (SIunit)
Bq equiv Number of disintegrations per second = 1 Bq = 1s
curie Ci equiv 37 times 1010 Bq = 37 times 1010 Bq [32]
rutherford (H) rd equiv 1 MBq = 1 times 106 Bq
Please note that although becquerel (Bq) and hertz (Hz) both ultimately refer to the same SI base unit (sminus1) Hz isused only for periodic phenomena and Bq is only used for stochastic processes associated with radioactivity[33]
Radiation - exposure
Radiation - exposure
Name of unit Symbol Definition Relation to SI units
roentgen R 1 R equiv 258 times 10minus4 Ckg[29] = 258 times 10minus4 Ckg
The roentgen is not a SI unit and the NIST strongly discourages its continued use[34]
Radiation - absorbed dose
Radiation - absorbed dose
Name of unit Symbol Definition Relation to SI units
Name of unit Symbol Definition Relation to SI units
Roumlntgen equivalent man rem equiv 001 Sv = 001 Sv
sievert (SI unit) Sv equiv 1 Jkg[33] = 1 Sv
Although the definitions for sievert (Sv) and gray (Gy) would seem to indicate that they measure the same quantitiesthis is not the case The effect of receiving a certain dose of radiation (given as Gy) is variable and depends on manyfactors thus a new unit was needed to denote the biological effectiveness of that dose on the body this is known asthe equivalent dose and is shown in Sv The general relationship between absorbed dose and equivalent dose can berepresented as
H = Q middot D
where H is the equivalent dose D is the absorbed dose and Q is a dimensionless quality factor Thus for anyquantity of D measured in Gy the numerical value for H measured in Sv may be different[36]
Conversion of units 27
Software toolsHome and office computers come with converters in bundled spreadsheet applications or can access free convertersvia the Internet Units and measurements can be easily converted using these tools but only if the units are explicitlydefined and the conversion is compatible (eg cmHg to kPa)
Free conversion softwarebull Units (software) a popular cross-platform command-line utilitybull Converter [37] contextual unit converter for Mozilla Firefox browsersbull Converber [38] portable application converting utilitybull calculla [39] calculla - online web convertersbull iMetrix [40] - unit converter for xpbull uniteasy [41] online scientific unit conversionbull Unit Converter Add-in for Excel [42] - allow a large selection of unit conversions within the Microsoft Excel
spread sheet programbull Unit Converter [43] simple and extensible unit converterbull Portable Unit Converter [44] including 4500 units 33 unit-categories and the possibility to create custom units
General commercial sources of convertersbull Advanced electronic calculators have unit-conversion functionalitybull Spreadsheet programs usually provide conversion functions or formulas or the user can write their ownbull Commercial mathematical scientific and technical applications often include converters
See also
bull Accuracy and precisionbull English unitsbull False precisionbull Imperial unitsbull International System of Unitsbull Mesures usuellesbull Metric system
bull Natural unitsbull Roundingbull Significant figuresbull Temperature conversionbull United States customary unitsbull Units conversion by factor-labelbull Units of measurement
External linksbull British law Units of measurement regulations 1995 [45]
bull ConvertBuster [46] Variety of conversion tools to convert easilybull How Many A dictionary of units of measurement [47]
bull NIST Fundamental physical constants mdash Non-SI units [48]PDF (357 KB)bull NIST Guide to SI Units [49] Many conversion factors listedbull Online Conversion Calculators [50] Very extensive list of conversions from-to equvalent unitsbull The Unified Code for Units of Measure [51]
bull Units Symbols and Conversions XML Dictionary [52]
bull Multilingual Online Conversion of Units [53]
bull Temperature Converter [54]
Conversion of units 28
References[1] United States Naval Observatory (2009) Selected Astronomical Constants 2009 (http asa usno navy mil SecK 2009
Astronomical_Constants_2009 txt) Accessed May 10 2009[2] NIST Reference on Constants Units and Uncertainty (http physics nist gov cgi-bin cuu Valuebohrrada0|search_for=Bohr+
radius)(2006) National Institute of Standards and Technology Retrieved February 22 2008[3] National Institute of Standards and Technology General Tables of Units of Measurement (http ts nist gov WeightsAndMeasures
Publications appxc cfm)[4] Lide D (Ed) (1990) Handbook of Chemistry and Physics (71st ed) Boca Raton FL CRC Press Section 1[5] National Bureau of Standards (June 30 1959) Refinement of values for the yard and the pound Federal Register viewed September 20
2006 at National Geodetic Survey web site (http www ngs noaa gov PUBS_LIB FedRegister FRdoc59-5442 pdf)[6] The International Astronomical Union and Astronomical Units (http www iau org public_press themes measuring )[7] Klein Herbert Arthur (1988) The Science of Measurement a Historical Survey Mineola NY Dover Publications 0-4862-5839-4[8] The International System of Units Section 21 (http www bipm org en si si_brochure chapter2 2-1 ) (8 ed) Bureau International des
Poids et Mesures 2006 retrieved August 26 2009[9] International System of Units (http www bipm org en si si_brochure chapter4 table8 html) 8th ed (2006) Bureau International des
Poids et Mesures Section 41 Table 8[10] P Kenneth Seidelmann Ed (1992) Explanatory Supplement to the Astronomical Almanac Sausalito CA University Science Books p 716
and sv parsec in Glossary[11] Whitelaw Ian (2007) A Measure of All Things The Story of Man and Measurement (http books google com
booksid=3zgGEWM5-iAC) New York Macmillan 0-312-37026-1 p 152[12] De Vinne Theodore Low (1900) The practice of typography a treatise on the processes of type-making the point system the names sizes
styles and prices of plain printing types (http books google com booksid=R4-DjphIpLMC) 2nd ed New York The Century Co p142ndash150
[13] Pasko Wesley Washington (1894) American dictionary of printing and bookmaking (http books google combooksid=Z_QUAAAAIAAJ) (1894) New York Howard Lockwood p 521
[14] Rowlett Russ (2005) How Many A Dictionary of Units of Measurement (http www unc edu ~rowlett units index html)[15] Thompson A and Taylor BN (2008) Guide for the Use of the International System of Units (SI) National Institute of Standards and
Technology Special Publication 811 p 57[16] US Code of Federal Regulations Title 21 Section 1019 Paragraph (b)(5)(viii) (http ecfr gpoaccess gov cgi t text text-idxc=ecframp
rgn=div8amp view=textamp node=212 0 1 1 2 1 1 6amp idno=21) retrieved August 29 2009[17] Barry N Taylor Ed NIST Special Publication 330 The International System of Units (SI) (http physics nist gov Pubs SP330 sp330
pdf) (2001 Edition) Washington US Government Printing Office 43The 12th Conference Generale des Poids et Mesures(CGPM)hellipdeclares that the word ldquolitrerdquo may be employed as a special name for the cubic decimetre
[18] CODATA Value atomic uint of mass (http physics nist gov cgi-bin cuu Valuettme|search_for=atomic+ unit+ of+ mass) (2006)National Institute of Standards and Technology Retrieved 16 September 2008
[19] The Swiss Federal Office for Metrology gives Zentner on a German language web page (http www metas ch de scales systemch html)and quintal on the English translation of that page (http www metas ch en scales systemch html) the unit is marked speacutecifiquementsuisse
[20] Pedersen O (1983) Glossary in Coyne G Hoskin M and Pedersen O Gregorian Reform of the Calendar Proceedings of the VaticanConference to Commemorate its 400th Anniversary Vatican Observatory Available from Astrophysics Data System
[21] Richards EG (1998) Mapping Time Oxford University Press pp 94ndash95 ISBN 0-19-850413-6[22] Steel Duncan (2000) Marking Time John Wiley amp Sons p 46 ISBN 0-471-29827-1[23] CODATA Value atomic unit of force (http physics nist gov cuu Constants ) (2006) National Institute of Standards and Technology
Retrieved September 14 2008[24] [[Comiteacute International des Poids et Mesures (http www bipm org en CIPM db 1946 2 )] Resolution 2] 1946 retrieved August 26
2009[25] Barry N Taylor (April 1995) Guide for the Use of the International System of Units (SI) (http physics nist gov cuu pdf sp811 pdf)
(NIST Special Publication 811) Washington DC US Government Printing Office pp 57ndash68[26] Barry N Taylor (April 1995) Guide for the Use of the International System of Units (SI) (NIST Special Publication 811) Washington DC
US Government Printing Office p 5[27] International System of Units (http www bipm org en si si_brochure chapter4 table7 html) 8th ed (2006) Bureau International des
Poids et Mesures Section 41 Table 7[28] The NIST Reference on Constants Units and Uncertainty (http physics nist gov cgi-bin cuu Valueauedm) 2006 retrieved August
26 2009[29] NIST Guide to SI Units Appendix B9 (http physics nist gov Pubs SP811 appenB9 html) retrieved August 27 2009[30] Standard for the Use of the International System of Units (SI) The Modern Metric System IEEEASTM SI 10-1997 (1997) New York and
West Conshohocken PA Institute of Electrical and Electronics Engineers and American Society for Testing and Materials Tables A1through A5
Conversion of units 29
[31] The NIST Reference on Constants Units and Uncertainty (http physics nist gov cuu Units candela html) retrieved August 28 2009[32] Ambler Thompson amp Barry N Taylor (2008) Guide for the Use of the International System of Units (SI) (http physics nist gov cuu
pdf sp811 pdf) Special Publication 811 Gaithersburg MD National Institute of Standards and Technology p 10[33] The International System of Units Section 222 Table 3 (http www bipm org en si si_brochure chapter2 2-2 table3 html) (8 ed)
Bureau International des Poids et Mesures 2006 retrieved August 27 2009[34] The NIST Guide to the SI (Special Publication 811) section 52 (http physics nist gov Pubs SP811 sec05 html5 2) 2008 retrieved
August 27 2009[35] Ambler Thompson amp Barry N Taylor (2008) Guide for the Use of the International System of Units (SI) (http physics nist gov cuu
pdf sp811 pdf) Special Publication 811 Gaithersburg MD National Institute of Standards and Technology p 5[36] [[Comiteacute international des poids et mesures (http www bipm org en CIPM db 2002 2 )] 2002 Recommendation 2] retrieved
August 27 2009[37] http converter mozdev org[38] http www xyntec com converber htm[39] http www calculla com[40] http illusions hu index phptask=100amp lang=0amp statpage=86[41] http www uniteasy com[42] http www tenderwire com wikipedialandingpage[43] http www kamlex com index phpoption=com_contentamp view=articleamp id=53amp Itemid=55[44] http www sttmedia com unitconverter[45] http www hmso gov uk si si1995 Uksi_19951804_en_2 htm[46] http www convertbuster com[47] http www unc edu ~rowlett units[48] http physics nist gov cuu Document nonsi_in_1998 pdf[49] http physics nist gov Pubs SP811 appenB9 html[50] http www onlineconversion com[51] http aurora rg iupui edu ~schadow units UCUM ucum html[52] http www posc org refs poscUnits20 xml[53] http www imperialtometric com[54] http www tampile com
Article Sources and Contributors 30
Article Sources and ContributorsConversion of units Source httpenwikipediaorgwindexphpoldid=373975089 Contributors 1571781xxx 7 A-giau AVSI Acather96 Ahoerstemeier Alexius08 Altenmann AndreEngels Andrewa Andy120290 Anonymi Ariconte Army1987 ArnoldReinhold Arthur3030 Aspects AxelBoldt AzaToth Azikala BW95 Bdesham Beland Bensaccount Bkumartvm Blackand White BlaiseFEgan BlueEarth Bobblewik Borbrav Bpmullins Bryan Derksen C J B Scholten CORNELIUSSEON CTZMSC3 Calltech Camerajohn Chaosfeary Charles MatthewsChris the speller Cmdrjameson Colonies Chris Conversion script Cope555 Crappy13 Crissov CyrilB DARTH SIDIOUS 2 DMacks DanielCD Dark Formal DarkestSideX DekisugiDenelson83 Dhp1080 Dicklyon DirkvdM Donald Duck Donarreiskoffer Dramatic Dyss DAringsbquougosz Egil Ehrenkater Ejohnsonboulder Elexmax Elf Emokhberi Enon Eob Epbr123Euchiasmus Fathead99 Father Goose Fella22 Femto FernandoAC Fibula Flutefreek Fred Bauder Fredrik Fuhghettaboutit Fuzheado Gaff Gene Nygaard Georgiy1996 Gerry AshtonGiftlite Gilliam Glenn L GoingBatty Goobergunch Gregsexton Greyengine5 Grunt Gurch Gutza HLHJ Haemo Hammersbach Heracles31 Herbee Heron HikerBush Hqb IcairnsIgiffin Indefatigable Isis JBobbitt JHunterJ Jabowery JakeVortex Jamicanmonkey Jason Begin Jay Jc3s5h Jcronen1 Jdoherty Jeffz1 Jeronimo Jimmuhk Jimp Jimwilliams57 JoeinwapJohndburger Josh Parris Jq4bagiq Kaihsu KaneWang Keenan Pepper Kevin Rector KeyStorm Khukri Kurtan Lee Daniel Crocker LightYear Linuxoidoz Liv4christ210 Loggie Lolo252Lupinelawyer M ichaeligl MJCdetroit MTC Mac MacMcF Magore Markus Kuhn Masterqwe MaxHund Maxamegalon2000 Mbeychok Meggar Mh26 Michael Daly Michael Hardy MichelAudy Mikelifeguard Mikhailov Kusserow Mindbuilder Missvain Monger Mr bulow MrOllie MrZhuKeeper Muro de Aguas Mwanner Mwtoews Nandesuka Natkeeran Ndsg NgjaimeNhy67ygv Nick Y Nick123 NickPenguin Ninjagecko Noe Nosilleg Now3r3 Obelix homologator Oldadamml Oleg Alexandrov Olivier Ortolan88 OwenBlacker Pac72 PassargeaPatrick Paul Martin Peter Horn Physchim62 Piels Pierdm Pmanderson Prometheus235 Quadell QuantumEleven Quod erat demonstrandum 314159 Radagast83 Rccoms RedWolfReinyday Revipm Rexparry sydney Reyk Rhetth Rhialto Rich Farmbrough Richard Myers Rjwilmsi Rlsheehan Robin Barry RoySmith Rpwolfgram SD6-Agent SGBailey SamuelLowry Samw Sander123 Seabhcan SebastianHelm Sherbert1 Shinhan Shrew Sietse Snel SimonP Sinbaddasail0r Skotte Smalljim SomeHuman Spencer Srleffler StarwarsmastergeekSteacoon StefanK SteveRamone Stevertigo Stokerm Suisui Sunev Superboy112233 Superm401 Synchronism Tacoman1996 Tarquin Taw Teratornis The Man in Question ThierrycThingg Thinking of England Thunderbird2 Timwi Tobias Hoevekamp Tomasr Tonsofpcs Toon05 Topsykretts2512 Trekphiler Tuwile Twanvl Uday147502 Unitman00 UrhixidurUtherSRG Vargenau Vsmith WarrenPlatts Wasell Welsh Whispering Wikinger Wolfkeeper Wtmitchell XJamRastafire Xenonice Yath Zginder Zibem Zocky Zotel 713 anonymousedits
slug per cubic foot slugft3 equiv slugft3 asymp 5153788184 kgm3
Time
Time t
Name of unit Symbol Definition Relation to SI units
atomic unit of time au equiv a0(αmiddotc) asymp 2418 884 254 times 10minus17
s
Callippic cycle equiv 441 mo (hollow) + 499 mo (full) = 76 a of 36525 d = 2398 3776 times 109 s
century c equiv 100 a (see below for definition of year length) = 100 times year
day d = 24 h = 86400 s
day (sidereal) d equiv Time needed for the Earth to rotate once around its axisdetermined from successive transits of a very distantastronomical object across an observers meridian(International Celestial Reference Frame)
asymp 86 1641 s
decade dec equiv 10 a (see below for definition of year length) = 10 times year
fortnight fn equiv 2 wk = 1 209 600 s
helek equiv 11 080 h = 33 s
Hipparchic cycle equiv 4 Callippic cycles - 1 d = 9593 424 times 109 s
hour h equiv 60 min = 3 600 s
jiffy j equiv 160 s = 016 s
jiffy (alternate) ja equiv 1100 s = 10 ms
ke (quarter of an hour) equiv frac14 h = 196 d = 60 times 60 4 s = 900 s= 60 4 min = 15 min
Conversion of units 13
ke (traditional) equiv 1100 d = 24 times 60 times 60 100 s =864 s = 24 60 100min = 144 min
lustre lustrum equiv 5 a of 365 d = 15768 times 108 s
Metonic cycle enneadecaeteris equiv 110 mo (hollow) + 125 mo (full) = 6940 d asymp 19 a = 5996 16 times 108 s
millennium equiv 1 000 a (see below for definition of year length) = 1000 times year
milliday md equiv 11 000 d = 24 times 60 times 60 1 000 s= 864 s
minute min equiv 60 s due to leap seconds sometimes 59 s or 61 s = 60 s
moment equiv 90 s = 90 s
month (full) mo equiv 30 d[20] = 2 592 000 s
month (Greg av) mo Average Gregorian month = 365242512 d = 30436875 d asymp 26297 times 106 s
month (hollow) mo equiv 29 d[20] = 2 505 600 s
month (synodic) mo Cycle time of moon phases asymp 29530589 days (Average) asymp 2551 times 106 s
octaeteris = 48 mo (full) + 48 mo (hollow) + 3 mo (full)[21] [22] = 8 aof 36525 d = 2922 d
= 2524 608 times 108 s
Planck time equiv (Gℏc5)frac12 asymp 1351 211 868 times 10minus43
s
second s time of 9 192 631 770 periods of the radiation correspondingto the transition between the 2 hyperfine levels of the groundstate of the caesium 133 atom at 0 K[8] (but other secondsare sometimes used in astronomy)
(SI base unit)
shake equiv 10minus8 s = 10 ns
sigma equiv 10minus6 s = 1 μs
Sothic cycle equiv 1 461 a of 365 d = 4607 4096 times 1010 s
svedberg S equiv 10minus13 s = 100 fs
week wk equiv 7 d = 604 800 s
year (Gregorian) a y oryr
= 3652425 d average calculated from common years (365d) plus leap years (366 d) on most years divisible by 4 Seeleap year for details
= 31 556 952 s
year (Julian) a y oryr
= 36525 d average calculated from common years (365 d)plus one leap year (366 d) every four years
= 31 557 600 s
year (sidereal) a y oryr
equiv time taken for Sun to return to the same position withrespect to the stars of the celestial sphere
asymp 365256 363 d asymp 31558 1497632 s
year (tropical) a y oryr
equiv Length of time it takes for the Sun to return to the sameposition in the cycle of seasons
asymp 365242 190 d asymp 31556 925 s
Where UTC is observed the length of timeunits longer than 1 s may increase or decreaseby 1 s if a leap second occurs during the timeinterval of interest
Conversion of units 14
Frequency
Frequency
Name of unit Symbol Definition Relation to SI units
hertz (SI unit) Hz equiv Number of cycles per second = 1 Hz = 1s
revolutions per minute rpm equiv One unit rpm equals one rotation completed around a fixed axis in one minute of time asymp0104719755 rads
Speed or velocity
Speed
Name of unit Symbol Definition Relation to SI units
foot per hour fph equiv 1 fth asymp 8466 667 times 10minus5
ms
foot per minute fpm equiv 1 ftmin = 508 times 10minus3 ms
foot per second fps equiv 1 fts = 3048 times 10minus1 ms
furlong perfortnight
equiv furlongfortnight asymp 1663 095 times 10minus4
ms
inch per minute ipm equiv 1 inmin asymp 423 333 times 10minus4 ms
inch per second ips equiv 1 ins = 254 times 10minus2 ms
mach number M Ratio of the speed to the speed of sound in the medium Varies especially with temperatureAbout 761 mph (1225 kph) in air at sea level to about 660 mph (1062 kph) at jet altitudesUnitless
asymp 340 to 295 ms foraircraft
metre per second(SI unit)
ms equiv 1 ms = 1 ms
mile per hour mph equiv 1 mih = 0447 04 ms
mile per minute mpm equiv 1 mimin = 268224 ms
mile per second mps equiv 1 mis = 1 609344 ms
speed of light invacuum
c equiv 299 792 458 ms = 299 792 458 ms
speed of sound inair
s Varies especially with temperature About 761 mph (1225 kph) in air at sea level to about660 mph (1062 kph) at jet altitudes
asymp 340 to 295 ms ataircraft altitudes
A velocity consists of a speed combined with a direction the speed part of the velocity takes units of speed
Conversion of units 15
Flow (volume)
Flow
Name of unit Symbol Definition Relation to SI units
cubic foot per minute CFM equiv 1 ft3min = 4719474432 times 10minus4 m3s
cubic foot per second ft3s equiv 1 ft3s = 0028316846592 m3s
cubic inch per minute in3min equiv 1 in3min = 27311773 times 10minus7 m3s
cubic inch per second in3s equiv 1 in3s = 16387064 times 10minus5 m3s
cubic metre per second (SIunit)
m3s equiv 1 m3s = 1 m3s
gallon (US fluid) per day GPD equiv 1 gald = 4381263638 times 10minus8 m3s
gallon (US fluid) per hour GPH equiv 1 galh = 1051503273 times 10minus6 m3s
gallon (US fluid) per minute GPM equiv 1 galmin = 630901964 times 10minus5 m3s
litre per minute LPM equiv 1 Lmin = 16 times 10minus5 m3s
Acceleration
Acceleration
Name of unit Symbol Definition Relation to SI units
foot per hour per second fphs equiv 1 ft(hmiddots) asymp 8466 667 times 10minus5
ms2
foot per minute per second fpms equiv 1 ft(minmiddots) = 508 times 10minus3 ms2
foot per second squared fps2 equiv 1 fts2 = 3048 times 10minus1 ms2
gal galileo Gal equiv 1 cms2 = 10minus2 ms2
inch per minute per second ipms equiv 1 in(minmiddots) asymp 4233 333 times 10minus4
ms2
inch per second squared ips2 equiv 1 ins2 = 254 times 10minus2 ms2
knot per second kns equiv 1 kns asymp 5144 444 times 10minus1
ms2
metre per second squared (SI unit) ms2 equiv 1 ms2 = 1 ms2
mile per hour per second mphs equiv 1 mi(hmiddots) = 44704 times 10minus1 ms2
mile per minute per second mpms equiv 1 mi(minmiddots) = 268224 ms2
mile per second squared mps2 equiv 1 mis2 = 1609 344 times 103 ms2
standard gravity g equiv 9806 65 ms2 = 9806 65 ms2
Conversion of units 16
Force
Force
Name of unit Symbol Definition Relation to SI units
atomic unit of force equiv memiddotα2middotc2a0 asymp 8238 722 06 times 10minus8 N
[23]
dyne (cgs unit) dyn equiv gmiddotcms2 = 10minus5 N
kilogram-force kilopondgrave-force
kgf kp Gf equiv g times 1 kg = 9806 65 N
kip kip-force kip kipfklbf
equiv g times 1 000 lb = 4448 221 6152605 times 103 N
milligrave-force gravet-force mGf gf equiv g times 1 g = 9806 65 mN
newton (SI unit) N A force capable of giving a mass of one kg an acceleration of one metreper second per second[24]
= 1 N = 1 kgmiddotms2
ounce-force ozf equiv g times 1 oz = 0278 013 850 9537812 N
pound lb equiv slugmiddotfts2 = 4448 230 531 N
pound-force lbf equiv g times 1 lb = 4448 221 615 2605 N
poise (cgs unit) P equiv 10minus1 Pamiddots = 01 Pamiddots
pound per foot hour lb(ftmiddoth) equiv 1 lb(ftmiddoth) asymp 4133 789 times 10minus4 Pamiddots
pound per foot second lb(ftmiddots) equiv 1 lb(ftmiddots) asymp 1488164 Pamiddots
pound-force second per square foot lbfmiddotsft2 equiv 1 lbfmiddotsft2 asymp 4788026 Pamiddots
pound-force second per square inch lbfmiddotsin2 equiv 1 lbfmiddotsin2 asymp 6894757 Pamiddots
Conversion of units 21
Kinematic viscosity
Kinematic viscosity
Name of unit Symbol Definition Relation to SI units
square foot per second ft2s equiv 1 ft2s = 009290304 m2s
square metre per second (SI unit) m2s equiv 1 m2s = 1 m2s
stokes (cgs unit) St equiv10minus4 m2s
= 10minus4 m2s
Electric current
Electric current
Name of unit Symbol Definition Relation to SI units
ampere (SI base unit) A equiv The constant current needed to produce a force of 2 times 10minus7 newton per metre betweentwo straight parallel conductors of infinite length and negligible circular cross-sectionplaced one metre apart in a vacuum[8]
= 1 A
electromagnetic unitabampere (cgs unit)
abamp equiv 10 A = 10 A
esu per secondstatampere (cgs unit)
esus equiv (01 Amiddotms) c asymp3335641 times 10minus10 A
Electric charge
Electric charge
Name of unit Symbol Definition Relation to SI units
abcoulomb electromagnetic unit (cgsunit)
abC emu equiv 10 C = 10 C
atomic unit of charge au equiv e asymp 1602 176462 times 10minus19 C
coulomb (SI unit) C equiv The amount of electricity carried in one second of time by oneampere of current[24]
= 1 C = 1 Amiddots
faraday F equiv 1 mol times NAmiddote asymp 96 4853383 C
statcoulomb franklin electrostatic unit(cgs unit)
statC Fresu
equiv (01 Amiddotm) c asymp 3335 641 times 10minus10 C
Conversion of units 22
Electric dipole
Electric dipole
Name of unit Symbol Definition Relation to SI units
atomic unit of electric dipole moment ea0 asymp 8478 352 81 times 10minus30
Cmiddotm[28]
Electromotive force electric potential difference
Voltage electromotive force
Name ofunit
Symbol Definition Relation to SI units
abvolt (cgsunit)
abV equiv 1 times 10minus8 V = 1 times 10minus8 V
statvolt (cgsunit)
statV equiv cmiddot (1 μJAmiddotm) = 299792 458 V
volt (SIunit)
V The difference in electric potential across two points along a conducting wire carrying one ampereof constant current when the power dissipated between the points equals one watt[24]
= 1 V = 1 WA = 1kgmiddotm2(Amiddots3)
Electrical resistance
Electrical resistance
Name ofunit
Symbol Definition Relation to SI units
ohm (SIunit)
Ω The resistance between two points in a conductor when one volt of electric potential differenceapplied to these points produces one ampere of current in the conductor[24]
= 1 Ω = 1 VA = 1kgmiddotm2(A2middots3)
Capacitance
Capacitors ability to store charge
Name ofunit
Symbol Definition Relation to SI units
farad (SIunit)
F The capacitance between two parallel plates that results in one volt of potential difference whencharged by one coulomb of electricity[24]
= 1 F = 1 CV = 1A2middots4(kgmiddotm2)
Conversion of units 23
Magnetic flux
magnetic flux
Name of unit Symbol Definition Relation to SI units
maxwell (CGSunit)
Mx equiv 10minus8 Wb[29] = 1 times 10minus8 Wb
weber (SIunit)
Wb Magnetic flux which linking a circuit of one turn would produce in it an electromotive force of1 volt if it were reduced to zero at a uniform rate in 1 second[24]
= 1 Wb = 1 Vmiddots = 1kgmiddotm2(Amiddots2)
Magnetic flux density
What physicists call Magnetic field is called Magnetic flux density by electrical engineersand magnetic induction by applied mathematicians and electrical engineers
Name of unit Symbol Definition Relation to SI units
gauss (CGS unit) G equiv Mxcm2 = 10minus4
T= 1 times 10minus4 T [30]
tesla (SI unit) T equiv Wbm2 = 1 T = 1 Wbm2 = 1kg(Amiddots2)
Inductance
Inductance
Name ofunit
Symbol Definition Relation to SI units
henry (SIunit)
H The inductance of a closed circuit that produces one volt of electromotive force when the current inthe circuit varies at a uniform rate of one ampere per second[24]
= 1 H = 1 WbA = 1kgmiddotm2(Amiddots)2
Temperature
Temperature
Name of unit Symbol Definition Conversion to kelvin
degree Celsius degC degC equiv K minus 27315 [K] equiv [degC] + 27315
degree Delisle degDe [K] = 37315 minus [degDe] times 23
degree Fahrenheit degF degF equiv degC times 95 + 32 [K] equiv ([degF] + 45967) times 59
degree Newton degN [K] = [degN] times 10033 + 27315
degree Rankine degR degRa degR equiv K times 95 [K] equiv [degR] times 59
degree Reacuteaumur degReacute [K] = [degReacute] times 54 + 27315
degree Roslashmer degRoslash [K] = ([degRoslash] minus 75) times 4021 + 27315
kelvin (SI baseunit)
K equiv 127316 of the thermodynamic temperature of the triple point of water[8] equiv 1 K
Conversion of units 24
Information entropy
Information entropy
Name of unit Symbol Definition Relation to SI units Relation to bits
SI unit JK equiv JK = 1 JK
nat nip nepit nat equiv kB = 1380 650 5(23) times 10minus23 JK
bit shannon bit b Sh equiv ln(2) times kB = 9569 940 (16) times 10minus24 JK = 1 bit
ban hartley ban Hart equiv ln(10) times kB = 3179 065 3(53) times 10minus23 JK
nibble equiv 4 bits = 3827 976 0(64) times 10minus23 JK = 22 bit
byte B equiv 8 bits = 7655 952 (13) times 10minus23 JK = 23 bit
kilobyte (decimal) kB equiv 1 000 B = 7655 952 (13) times 10minus20 JK
kilobyte (kibibyte) KB KiB equiv 1 024 B = 7839 695 (13) times 10minus20 JK = 210 bit
Often information entropy is measured in shannons whereas the (discrete) storage space of digital devices ismeasured in bits Thus uncompressed redundant data occupy more than one bit of storage per shannon ofinformation entropy The multiples of a bit listed above are usually used with this meaning Other times the bit isused as a measure of information entropy and is thus a synonym of shannon
Luminous intensityThe candela is the preferred nomenclature for the SI unit
Luminous intensity
Name of unit Symbol Definition Relation toSI units
candela (SI baseunit) candle
cd The luminous intensity in a given direction of a source that emits monochromatic radiation offrequency 540 times 1012 hertz and that has a radiant intensity in that direction of 1683 watt persteradian[8]
= 1 cd
candlepower (new) cp equiv cd The use of candlepower as a unit is discouraged due to its ambiguity = 1 cd
candlepower (oldpre-1948)
cp Varies and is poorly reproducible[31] Approximately 0981 cd[14] asymp 0981 cd
Luminance
Conversion of units 25
Luminance
Name of unit Symbol Definition Relation to SI units
candela per square foot cdft2 equiv cdft2 asymp10763910417 cdm2
candela per square inch cdin2 equiv cdin2 asymp 15500031 cdm2
candela per square metre (SI unit) nit (deprecated[14] ) cdm2 equiv cdm2 = 1 cdm2
Name of unit Symbol Definition Relation to SI units
lumen (SIunit)
lm equiv cdmiddotsr = 1 lm = 1 cdmiddotsr
Illuminance
Illuminance
Name of unit Symbol Definition Relation to SI units
footcandle lumen per square foot fc equiv lmft2 = 10763910417 lx
lumen per square inch lmin2 equiv lmin2 asymp 15500031 lx
lux (SI unit) lx equiv lmm2 = 1 lx = 1 lmm2
phot (CGS unit) ph equiv lmcm2 = 1 times 104 lx
Radiation - source activity
Conversion of units 26
Radioactivity
Name of unit Symbol Definition Relation to SI units
becquerel (SIunit)
Bq equiv Number of disintegrations per second = 1 Bq = 1s
curie Ci equiv 37 times 1010 Bq = 37 times 1010 Bq [32]
rutherford (H) rd equiv 1 MBq = 1 times 106 Bq
Please note that although becquerel (Bq) and hertz (Hz) both ultimately refer to the same SI base unit (sminus1) Hz isused only for periodic phenomena and Bq is only used for stochastic processes associated with radioactivity[33]
Radiation - exposure
Radiation - exposure
Name of unit Symbol Definition Relation to SI units
roentgen R 1 R equiv 258 times 10minus4 Ckg[29] = 258 times 10minus4 Ckg
The roentgen is not a SI unit and the NIST strongly discourages its continued use[34]
Radiation - absorbed dose
Radiation - absorbed dose
Name of unit Symbol Definition Relation to SI units
Name of unit Symbol Definition Relation to SI units
Roumlntgen equivalent man rem equiv 001 Sv = 001 Sv
sievert (SI unit) Sv equiv 1 Jkg[33] = 1 Sv
Although the definitions for sievert (Sv) and gray (Gy) would seem to indicate that they measure the same quantitiesthis is not the case The effect of receiving a certain dose of radiation (given as Gy) is variable and depends on manyfactors thus a new unit was needed to denote the biological effectiveness of that dose on the body this is known asthe equivalent dose and is shown in Sv The general relationship between absorbed dose and equivalent dose can berepresented as
H = Q middot D
where H is the equivalent dose D is the absorbed dose and Q is a dimensionless quality factor Thus for anyquantity of D measured in Gy the numerical value for H measured in Sv may be different[36]
Conversion of units 27
Software toolsHome and office computers come with converters in bundled spreadsheet applications or can access free convertersvia the Internet Units and measurements can be easily converted using these tools but only if the units are explicitlydefined and the conversion is compatible (eg cmHg to kPa)
Free conversion softwarebull Units (software) a popular cross-platform command-line utilitybull Converter [37] contextual unit converter for Mozilla Firefox browsersbull Converber [38] portable application converting utilitybull calculla [39] calculla - online web convertersbull iMetrix [40] - unit converter for xpbull uniteasy [41] online scientific unit conversionbull Unit Converter Add-in for Excel [42] - allow a large selection of unit conversions within the Microsoft Excel
spread sheet programbull Unit Converter [43] simple and extensible unit converterbull Portable Unit Converter [44] including 4500 units 33 unit-categories and the possibility to create custom units
General commercial sources of convertersbull Advanced electronic calculators have unit-conversion functionalitybull Spreadsheet programs usually provide conversion functions or formulas or the user can write their ownbull Commercial mathematical scientific and technical applications often include converters
See also
bull Accuracy and precisionbull English unitsbull False precisionbull Imperial unitsbull International System of Unitsbull Mesures usuellesbull Metric system
bull Natural unitsbull Roundingbull Significant figuresbull Temperature conversionbull United States customary unitsbull Units conversion by factor-labelbull Units of measurement
External linksbull British law Units of measurement regulations 1995 [45]
bull ConvertBuster [46] Variety of conversion tools to convert easilybull How Many A dictionary of units of measurement [47]
bull NIST Fundamental physical constants mdash Non-SI units [48]PDF (357 KB)bull NIST Guide to SI Units [49] Many conversion factors listedbull Online Conversion Calculators [50] Very extensive list of conversions from-to equvalent unitsbull The Unified Code for Units of Measure [51]
bull Units Symbols and Conversions XML Dictionary [52]
bull Multilingual Online Conversion of Units [53]
bull Temperature Converter [54]
Conversion of units 28
References[1] United States Naval Observatory (2009) Selected Astronomical Constants 2009 (http asa usno navy mil SecK 2009
Astronomical_Constants_2009 txt) Accessed May 10 2009[2] NIST Reference on Constants Units and Uncertainty (http physics nist gov cgi-bin cuu Valuebohrrada0|search_for=Bohr+
radius)(2006) National Institute of Standards and Technology Retrieved February 22 2008[3] National Institute of Standards and Technology General Tables of Units of Measurement (http ts nist gov WeightsAndMeasures
Publications appxc cfm)[4] Lide D (Ed) (1990) Handbook of Chemistry and Physics (71st ed) Boca Raton FL CRC Press Section 1[5] National Bureau of Standards (June 30 1959) Refinement of values for the yard and the pound Federal Register viewed September 20
2006 at National Geodetic Survey web site (http www ngs noaa gov PUBS_LIB FedRegister FRdoc59-5442 pdf)[6] The International Astronomical Union and Astronomical Units (http www iau org public_press themes measuring )[7] Klein Herbert Arthur (1988) The Science of Measurement a Historical Survey Mineola NY Dover Publications 0-4862-5839-4[8] The International System of Units Section 21 (http www bipm org en si si_brochure chapter2 2-1 ) (8 ed) Bureau International des
Poids et Mesures 2006 retrieved August 26 2009[9] International System of Units (http www bipm org en si si_brochure chapter4 table8 html) 8th ed (2006) Bureau International des
Poids et Mesures Section 41 Table 8[10] P Kenneth Seidelmann Ed (1992) Explanatory Supplement to the Astronomical Almanac Sausalito CA University Science Books p 716
and sv parsec in Glossary[11] Whitelaw Ian (2007) A Measure of All Things The Story of Man and Measurement (http books google com
booksid=3zgGEWM5-iAC) New York Macmillan 0-312-37026-1 p 152[12] De Vinne Theodore Low (1900) The practice of typography a treatise on the processes of type-making the point system the names sizes
styles and prices of plain printing types (http books google com booksid=R4-DjphIpLMC) 2nd ed New York The Century Co p142ndash150
[13] Pasko Wesley Washington (1894) American dictionary of printing and bookmaking (http books google combooksid=Z_QUAAAAIAAJ) (1894) New York Howard Lockwood p 521
[14] Rowlett Russ (2005) How Many A Dictionary of Units of Measurement (http www unc edu ~rowlett units index html)[15] Thompson A and Taylor BN (2008) Guide for the Use of the International System of Units (SI) National Institute of Standards and
Technology Special Publication 811 p 57[16] US Code of Federal Regulations Title 21 Section 1019 Paragraph (b)(5)(viii) (http ecfr gpoaccess gov cgi t text text-idxc=ecframp
rgn=div8amp view=textamp node=212 0 1 1 2 1 1 6amp idno=21) retrieved August 29 2009[17] Barry N Taylor Ed NIST Special Publication 330 The International System of Units (SI) (http physics nist gov Pubs SP330 sp330
pdf) (2001 Edition) Washington US Government Printing Office 43The 12th Conference Generale des Poids et Mesures(CGPM)hellipdeclares that the word ldquolitrerdquo may be employed as a special name for the cubic decimetre
[18] CODATA Value atomic uint of mass (http physics nist gov cgi-bin cuu Valuettme|search_for=atomic+ unit+ of+ mass) (2006)National Institute of Standards and Technology Retrieved 16 September 2008
[19] The Swiss Federal Office for Metrology gives Zentner on a German language web page (http www metas ch de scales systemch html)and quintal on the English translation of that page (http www metas ch en scales systemch html) the unit is marked speacutecifiquementsuisse
[20] Pedersen O (1983) Glossary in Coyne G Hoskin M and Pedersen O Gregorian Reform of the Calendar Proceedings of the VaticanConference to Commemorate its 400th Anniversary Vatican Observatory Available from Astrophysics Data System
[21] Richards EG (1998) Mapping Time Oxford University Press pp 94ndash95 ISBN 0-19-850413-6[22] Steel Duncan (2000) Marking Time John Wiley amp Sons p 46 ISBN 0-471-29827-1[23] CODATA Value atomic unit of force (http physics nist gov cuu Constants ) (2006) National Institute of Standards and Technology
Retrieved September 14 2008[24] [[Comiteacute International des Poids et Mesures (http www bipm org en CIPM db 1946 2 )] Resolution 2] 1946 retrieved August 26
2009[25] Barry N Taylor (April 1995) Guide for the Use of the International System of Units (SI) (http physics nist gov cuu pdf sp811 pdf)
(NIST Special Publication 811) Washington DC US Government Printing Office pp 57ndash68[26] Barry N Taylor (April 1995) Guide for the Use of the International System of Units (SI) (NIST Special Publication 811) Washington DC
US Government Printing Office p 5[27] International System of Units (http www bipm org en si si_brochure chapter4 table7 html) 8th ed (2006) Bureau International des
Poids et Mesures Section 41 Table 7[28] The NIST Reference on Constants Units and Uncertainty (http physics nist gov cgi-bin cuu Valueauedm) 2006 retrieved August
26 2009[29] NIST Guide to SI Units Appendix B9 (http physics nist gov Pubs SP811 appenB9 html) retrieved August 27 2009[30] Standard for the Use of the International System of Units (SI) The Modern Metric System IEEEASTM SI 10-1997 (1997) New York and
West Conshohocken PA Institute of Electrical and Electronics Engineers and American Society for Testing and Materials Tables A1through A5
Conversion of units 29
[31] The NIST Reference on Constants Units and Uncertainty (http physics nist gov cuu Units candela html) retrieved August 28 2009[32] Ambler Thompson amp Barry N Taylor (2008) Guide for the Use of the International System of Units (SI) (http physics nist gov cuu
pdf sp811 pdf) Special Publication 811 Gaithersburg MD National Institute of Standards and Technology p 10[33] The International System of Units Section 222 Table 3 (http www bipm org en si si_brochure chapter2 2-2 table3 html) (8 ed)
Bureau International des Poids et Mesures 2006 retrieved August 27 2009[34] The NIST Guide to the SI (Special Publication 811) section 52 (http physics nist gov Pubs SP811 sec05 html5 2) 2008 retrieved
August 27 2009[35] Ambler Thompson amp Barry N Taylor (2008) Guide for the Use of the International System of Units (SI) (http physics nist gov cuu
pdf sp811 pdf) Special Publication 811 Gaithersburg MD National Institute of Standards and Technology p 5[36] [[Comiteacute international des poids et mesures (http www bipm org en CIPM db 2002 2 )] 2002 Recommendation 2] retrieved
August 27 2009[37] http converter mozdev org[38] http www xyntec com converber htm[39] http www calculla com[40] http illusions hu index phptask=100amp lang=0amp statpage=86[41] http www uniteasy com[42] http www tenderwire com wikipedialandingpage[43] http www kamlex com index phpoption=com_contentamp view=articleamp id=53amp Itemid=55[44] http www sttmedia com unitconverter[45] http www hmso gov uk si si1995 Uksi_19951804_en_2 htm[46] http www convertbuster com[47] http www unc edu ~rowlett units[48] http physics nist gov cuu Document nonsi_in_1998 pdf[49] http physics nist gov Pubs SP811 appenB9 html[50] http www onlineconversion com[51] http aurora rg iupui edu ~schadow units UCUM ucum html[52] http www posc org refs poscUnits20 xml[53] http www imperialtometric com[54] http www tampile com
Article Sources and Contributors 30
Article Sources and ContributorsConversion of units Source httpenwikipediaorgwindexphpoldid=373975089 Contributors 1571781xxx 7 A-giau AVSI Acather96 Ahoerstemeier Alexius08 Altenmann AndreEngels Andrewa Andy120290 Anonymi Ariconte Army1987 ArnoldReinhold Arthur3030 Aspects AxelBoldt AzaToth Azikala BW95 Bdesham Beland Bensaccount Bkumartvm Blackand White BlaiseFEgan BlueEarth Bobblewik Borbrav Bpmullins Bryan Derksen C J B Scholten CORNELIUSSEON CTZMSC3 Calltech Camerajohn Chaosfeary Charles MatthewsChris the speller Cmdrjameson Colonies Chris Conversion script Cope555 Crappy13 Crissov CyrilB DARTH SIDIOUS 2 DMacks DanielCD Dark Formal DarkestSideX DekisugiDenelson83 Dhp1080 Dicklyon DirkvdM Donald Duck Donarreiskoffer Dramatic Dyss DAringsbquougosz Egil Ehrenkater Ejohnsonboulder Elexmax Elf Emokhberi Enon Eob Epbr123Euchiasmus Fathead99 Father Goose Fella22 Femto FernandoAC Fibula Flutefreek Fred Bauder Fredrik Fuhghettaboutit Fuzheado Gaff Gene Nygaard Georgiy1996 Gerry AshtonGiftlite Gilliam Glenn L GoingBatty Goobergunch Gregsexton Greyengine5 Grunt Gurch Gutza HLHJ Haemo Hammersbach Heracles31 Herbee Heron HikerBush Hqb IcairnsIgiffin Indefatigable Isis JBobbitt JHunterJ Jabowery JakeVortex Jamicanmonkey Jason Begin Jay Jc3s5h Jcronen1 Jdoherty Jeffz1 Jeronimo Jimmuhk Jimp Jimwilliams57 JoeinwapJohndburger Josh Parris Jq4bagiq Kaihsu KaneWang Keenan Pepper Kevin Rector KeyStorm Khukri Kurtan Lee Daniel Crocker LightYear Linuxoidoz Liv4christ210 Loggie Lolo252Lupinelawyer M ichaeligl MJCdetroit MTC Mac MacMcF Magore Markus Kuhn Masterqwe MaxHund Maxamegalon2000 Mbeychok Meggar Mh26 Michael Daly Michael Hardy MichelAudy Mikelifeguard Mikhailov Kusserow Mindbuilder Missvain Monger Mr bulow MrOllie MrZhuKeeper Muro de Aguas Mwanner Mwtoews Nandesuka Natkeeran Ndsg NgjaimeNhy67ygv Nick Y Nick123 NickPenguin Ninjagecko Noe Nosilleg Now3r3 Obelix homologator Oldadamml Oleg Alexandrov Olivier Ortolan88 OwenBlacker Pac72 PassargeaPatrick Paul Martin Peter Horn Physchim62 Piels Pierdm Pmanderson Prometheus235 Quadell QuantumEleven Quod erat demonstrandum 314159 Radagast83 Rccoms RedWolfReinyday Revipm Rexparry sydney Reyk Rhetth Rhialto Rich Farmbrough Richard Myers Rjwilmsi Rlsheehan Robin Barry RoySmith Rpwolfgram SD6-Agent SGBailey SamuelLowry Samw Sander123 Seabhcan SebastianHelm Sherbert1 Shinhan Shrew Sietse Snel SimonP Sinbaddasail0r Skotte Smalljim SomeHuman Spencer Srleffler StarwarsmastergeekSteacoon StefanK SteveRamone Stevertigo Stokerm Suisui Sunev Superboy112233 Superm401 Synchronism Tacoman1996 Tarquin Taw Teratornis The Man in Question ThierrycThingg Thinking of England Thunderbird2 Timwi Tobias Hoevekamp Tomasr Tonsofpcs Toon05 Topsykretts2512 Trekphiler Tuwile Twanvl Uday147502 Unitman00 UrhixidurUtherSRG Vargenau Vsmith WarrenPlatts Wasell Welsh Whispering Wikinger Wolfkeeper Wtmitchell XJamRastafire Xenonice Yath Zginder Zibem Zocky Zotel 713 anonymousedits
ke (traditional) equiv 1100 d = 24 times 60 times 60 100 s =864 s = 24 60 100min = 144 min
lustre lustrum equiv 5 a of 365 d = 15768 times 108 s
Metonic cycle enneadecaeteris equiv 110 mo (hollow) + 125 mo (full) = 6940 d asymp 19 a = 5996 16 times 108 s
millennium equiv 1 000 a (see below for definition of year length) = 1000 times year
milliday md equiv 11 000 d = 24 times 60 times 60 1 000 s= 864 s
minute min equiv 60 s due to leap seconds sometimes 59 s or 61 s = 60 s
moment equiv 90 s = 90 s
month (full) mo equiv 30 d[20] = 2 592 000 s
month (Greg av) mo Average Gregorian month = 365242512 d = 30436875 d asymp 26297 times 106 s
month (hollow) mo equiv 29 d[20] = 2 505 600 s
month (synodic) mo Cycle time of moon phases asymp 29530589 days (Average) asymp 2551 times 106 s
octaeteris = 48 mo (full) + 48 mo (hollow) + 3 mo (full)[21] [22] = 8 aof 36525 d = 2922 d
= 2524 608 times 108 s
Planck time equiv (Gℏc5)frac12 asymp 1351 211 868 times 10minus43
s
second s time of 9 192 631 770 periods of the radiation correspondingto the transition between the 2 hyperfine levels of the groundstate of the caesium 133 atom at 0 K[8] (but other secondsare sometimes used in astronomy)
(SI base unit)
shake equiv 10minus8 s = 10 ns
sigma equiv 10minus6 s = 1 μs
Sothic cycle equiv 1 461 a of 365 d = 4607 4096 times 1010 s
svedberg S equiv 10minus13 s = 100 fs
week wk equiv 7 d = 604 800 s
year (Gregorian) a y oryr
= 3652425 d average calculated from common years (365d) plus leap years (366 d) on most years divisible by 4 Seeleap year for details
= 31 556 952 s
year (Julian) a y oryr
= 36525 d average calculated from common years (365 d)plus one leap year (366 d) every four years
= 31 557 600 s
year (sidereal) a y oryr
equiv time taken for Sun to return to the same position withrespect to the stars of the celestial sphere
asymp 365256 363 d asymp 31558 1497632 s
year (tropical) a y oryr
equiv Length of time it takes for the Sun to return to the sameposition in the cycle of seasons
asymp 365242 190 d asymp 31556 925 s
Where UTC is observed the length of timeunits longer than 1 s may increase or decreaseby 1 s if a leap second occurs during the timeinterval of interest
Conversion of units 14
Frequency
Frequency
Name of unit Symbol Definition Relation to SI units
hertz (SI unit) Hz equiv Number of cycles per second = 1 Hz = 1s
revolutions per minute rpm equiv One unit rpm equals one rotation completed around a fixed axis in one minute of time asymp0104719755 rads
Speed or velocity
Speed
Name of unit Symbol Definition Relation to SI units
foot per hour fph equiv 1 fth asymp 8466 667 times 10minus5
ms
foot per minute fpm equiv 1 ftmin = 508 times 10minus3 ms
foot per second fps equiv 1 fts = 3048 times 10minus1 ms
furlong perfortnight
equiv furlongfortnight asymp 1663 095 times 10minus4
ms
inch per minute ipm equiv 1 inmin asymp 423 333 times 10minus4 ms
inch per second ips equiv 1 ins = 254 times 10minus2 ms
mach number M Ratio of the speed to the speed of sound in the medium Varies especially with temperatureAbout 761 mph (1225 kph) in air at sea level to about 660 mph (1062 kph) at jet altitudesUnitless
asymp 340 to 295 ms foraircraft
metre per second(SI unit)
ms equiv 1 ms = 1 ms
mile per hour mph equiv 1 mih = 0447 04 ms
mile per minute mpm equiv 1 mimin = 268224 ms
mile per second mps equiv 1 mis = 1 609344 ms
speed of light invacuum
c equiv 299 792 458 ms = 299 792 458 ms
speed of sound inair
s Varies especially with temperature About 761 mph (1225 kph) in air at sea level to about660 mph (1062 kph) at jet altitudes
asymp 340 to 295 ms ataircraft altitudes
A velocity consists of a speed combined with a direction the speed part of the velocity takes units of speed
Conversion of units 15
Flow (volume)
Flow
Name of unit Symbol Definition Relation to SI units
cubic foot per minute CFM equiv 1 ft3min = 4719474432 times 10minus4 m3s
cubic foot per second ft3s equiv 1 ft3s = 0028316846592 m3s
cubic inch per minute in3min equiv 1 in3min = 27311773 times 10minus7 m3s
cubic inch per second in3s equiv 1 in3s = 16387064 times 10minus5 m3s
cubic metre per second (SIunit)
m3s equiv 1 m3s = 1 m3s
gallon (US fluid) per day GPD equiv 1 gald = 4381263638 times 10minus8 m3s
gallon (US fluid) per hour GPH equiv 1 galh = 1051503273 times 10minus6 m3s
gallon (US fluid) per minute GPM equiv 1 galmin = 630901964 times 10minus5 m3s
litre per minute LPM equiv 1 Lmin = 16 times 10minus5 m3s
Acceleration
Acceleration
Name of unit Symbol Definition Relation to SI units
foot per hour per second fphs equiv 1 ft(hmiddots) asymp 8466 667 times 10minus5
ms2
foot per minute per second fpms equiv 1 ft(minmiddots) = 508 times 10minus3 ms2
foot per second squared fps2 equiv 1 fts2 = 3048 times 10minus1 ms2
gal galileo Gal equiv 1 cms2 = 10minus2 ms2
inch per minute per second ipms equiv 1 in(minmiddots) asymp 4233 333 times 10minus4
ms2
inch per second squared ips2 equiv 1 ins2 = 254 times 10minus2 ms2
knot per second kns equiv 1 kns asymp 5144 444 times 10minus1
ms2
metre per second squared (SI unit) ms2 equiv 1 ms2 = 1 ms2
mile per hour per second mphs equiv 1 mi(hmiddots) = 44704 times 10minus1 ms2
mile per minute per second mpms equiv 1 mi(minmiddots) = 268224 ms2
mile per second squared mps2 equiv 1 mis2 = 1609 344 times 103 ms2
standard gravity g equiv 9806 65 ms2 = 9806 65 ms2
Conversion of units 16
Force
Force
Name of unit Symbol Definition Relation to SI units
atomic unit of force equiv memiddotα2middotc2a0 asymp 8238 722 06 times 10minus8 N
[23]
dyne (cgs unit) dyn equiv gmiddotcms2 = 10minus5 N
kilogram-force kilopondgrave-force
kgf kp Gf equiv g times 1 kg = 9806 65 N
kip kip-force kip kipfklbf
equiv g times 1 000 lb = 4448 221 6152605 times 103 N
milligrave-force gravet-force mGf gf equiv g times 1 g = 9806 65 mN
newton (SI unit) N A force capable of giving a mass of one kg an acceleration of one metreper second per second[24]
= 1 N = 1 kgmiddotms2
ounce-force ozf equiv g times 1 oz = 0278 013 850 9537812 N
pound lb equiv slugmiddotfts2 = 4448 230 531 N
pound-force lbf equiv g times 1 lb = 4448 221 615 2605 N
poise (cgs unit) P equiv 10minus1 Pamiddots = 01 Pamiddots
pound per foot hour lb(ftmiddoth) equiv 1 lb(ftmiddoth) asymp 4133 789 times 10minus4 Pamiddots
pound per foot second lb(ftmiddots) equiv 1 lb(ftmiddots) asymp 1488164 Pamiddots
pound-force second per square foot lbfmiddotsft2 equiv 1 lbfmiddotsft2 asymp 4788026 Pamiddots
pound-force second per square inch lbfmiddotsin2 equiv 1 lbfmiddotsin2 asymp 6894757 Pamiddots
Conversion of units 21
Kinematic viscosity
Kinematic viscosity
Name of unit Symbol Definition Relation to SI units
square foot per second ft2s equiv 1 ft2s = 009290304 m2s
square metre per second (SI unit) m2s equiv 1 m2s = 1 m2s
stokes (cgs unit) St equiv10minus4 m2s
= 10minus4 m2s
Electric current
Electric current
Name of unit Symbol Definition Relation to SI units
ampere (SI base unit) A equiv The constant current needed to produce a force of 2 times 10minus7 newton per metre betweentwo straight parallel conductors of infinite length and negligible circular cross-sectionplaced one metre apart in a vacuum[8]
= 1 A
electromagnetic unitabampere (cgs unit)
abamp equiv 10 A = 10 A
esu per secondstatampere (cgs unit)
esus equiv (01 Amiddotms) c asymp3335641 times 10minus10 A
Electric charge
Electric charge
Name of unit Symbol Definition Relation to SI units
abcoulomb electromagnetic unit (cgsunit)
abC emu equiv 10 C = 10 C
atomic unit of charge au equiv e asymp 1602 176462 times 10minus19 C
coulomb (SI unit) C equiv The amount of electricity carried in one second of time by oneampere of current[24]
= 1 C = 1 Amiddots
faraday F equiv 1 mol times NAmiddote asymp 96 4853383 C
statcoulomb franklin electrostatic unit(cgs unit)
statC Fresu
equiv (01 Amiddotm) c asymp 3335 641 times 10minus10 C
Conversion of units 22
Electric dipole
Electric dipole
Name of unit Symbol Definition Relation to SI units
atomic unit of electric dipole moment ea0 asymp 8478 352 81 times 10minus30
Cmiddotm[28]
Electromotive force electric potential difference
Voltage electromotive force
Name ofunit
Symbol Definition Relation to SI units
abvolt (cgsunit)
abV equiv 1 times 10minus8 V = 1 times 10minus8 V
statvolt (cgsunit)
statV equiv cmiddot (1 μJAmiddotm) = 299792 458 V
volt (SIunit)
V The difference in electric potential across two points along a conducting wire carrying one ampereof constant current when the power dissipated between the points equals one watt[24]
= 1 V = 1 WA = 1kgmiddotm2(Amiddots3)
Electrical resistance
Electrical resistance
Name ofunit
Symbol Definition Relation to SI units
ohm (SIunit)
Ω The resistance between two points in a conductor when one volt of electric potential differenceapplied to these points produces one ampere of current in the conductor[24]
= 1 Ω = 1 VA = 1kgmiddotm2(A2middots3)
Capacitance
Capacitors ability to store charge
Name ofunit
Symbol Definition Relation to SI units
farad (SIunit)
F The capacitance between two parallel plates that results in one volt of potential difference whencharged by one coulomb of electricity[24]
= 1 F = 1 CV = 1A2middots4(kgmiddotm2)
Conversion of units 23
Magnetic flux
magnetic flux
Name of unit Symbol Definition Relation to SI units
maxwell (CGSunit)
Mx equiv 10minus8 Wb[29] = 1 times 10minus8 Wb
weber (SIunit)
Wb Magnetic flux which linking a circuit of one turn would produce in it an electromotive force of1 volt if it were reduced to zero at a uniform rate in 1 second[24]
= 1 Wb = 1 Vmiddots = 1kgmiddotm2(Amiddots2)
Magnetic flux density
What physicists call Magnetic field is called Magnetic flux density by electrical engineersand magnetic induction by applied mathematicians and electrical engineers
Name of unit Symbol Definition Relation to SI units
gauss (CGS unit) G equiv Mxcm2 = 10minus4
T= 1 times 10minus4 T [30]
tesla (SI unit) T equiv Wbm2 = 1 T = 1 Wbm2 = 1kg(Amiddots2)
Inductance
Inductance
Name ofunit
Symbol Definition Relation to SI units
henry (SIunit)
H The inductance of a closed circuit that produces one volt of electromotive force when the current inthe circuit varies at a uniform rate of one ampere per second[24]
= 1 H = 1 WbA = 1kgmiddotm2(Amiddots)2
Temperature
Temperature
Name of unit Symbol Definition Conversion to kelvin
degree Celsius degC degC equiv K minus 27315 [K] equiv [degC] + 27315
degree Delisle degDe [K] = 37315 minus [degDe] times 23
degree Fahrenheit degF degF equiv degC times 95 + 32 [K] equiv ([degF] + 45967) times 59
degree Newton degN [K] = [degN] times 10033 + 27315
degree Rankine degR degRa degR equiv K times 95 [K] equiv [degR] times 59
degree Reacuteaumur degReacute [K] = [degReacute] times 54 + 27315
degree Roslashmer degRoslash [K] = ([degRoslash] minus 75) times 4021 + 27315
kelvin (SI baseunit)
K equiv 127316 of the thermodynamic temperature of the triple point of water[8] equiv 1 K
Conversion of units 24
Information entropy
Information entropy
Name of unit Symbol Definition Relation to SI units Relation to bits
SI unit JK equiv JK = 1 JK
nat nip nepit nat equiv kB = 1380 650 5(23) times 10minus23 JK
bit shannon bit b Sh equiv ln(2) times kB = 9569 940 (16) times 10minus24 JK = 1 bit
ban hartley ban Hart equiv ln(10) times kB = 3179 065 3(53) times 10minus23 JK
nibble equiv 4 bits = 3827 976 0(64) times 10minus23 JK = 22 bit
byte B equiv 8 bits = 7655 952 (13) times 10minus23 JK = 23 bit
kilobyte (decimal) kB equiv 1 000 B = 7655 952 (13) times 10minus20 JK
kilobyte (kibibyte) KB KiB equiv 1 024 B = 7839 695 (13) times 10minus20 JK = 210 bit
Often information entropy is measured in shannons whereas the (discrete) storage space of digital devices ismeasured in bits Thus uncompressed redundant data occupy more than one bit of storage per shannon ofinformation entropy The multiples of a bit listed above are usually used with this meaning Other times the bit isused as a measure of information entropy and is thus a synonym of shannon
Luminous intensityThe candela is the preferred nomenclature for the SI unit
Luminous intensity
Name of unit Symbol Definition Relation toSI units
candela (SI baseunit) candle
cd The luminous intensity in a given direction of a source that emits monochromatic radiation offrequency 540 times 1012 hertz and that has a radiant intensity in that direction of 1683 watt persteradian[8]
= 1 cd
candlepower (new) cp equiv cd The use of candlepower as a unit is discouraged due to its ambiguity = 1 cd
candlepower (oldpre-1948)
cp Varies and is poorly reproducible[31] Approximately 0981 cd[14] asymp 0981 cd
Luminance
Conversion of units 25
Luminance
Name of unit Symbol Definition Relation to SI units
candela per square foot cdft2 equiv cdft2 asymp10763910417 cdm2
candela per square inch cdin2 equiv cdin2 asymp 15500031 cdm2
candela per square metre (SI unit) nit (deprecated[14] ) cdm2 equiv cdm2 = 1 cdm2
Name of unit Symbol Definition Relation to SI units
lumen (SIunit)
lm equiv cdmiddotsr = 1 lm = 1 cdmiddotsr
Illuminance
Illuminance
Name of unit Symbol Definition Relation to SI units
footcandle lumen per square foot fc equiv lmft2 = 10763910417 lx
lumen per square inch lmin2 equiv lmin2 asymp 15500031 lx
lux (SI unit) lx equiv lmm2 = 1 lx = 1 lmm2
phot (CGS unit) ph equiv lmcm2 = 1 times 104 lx
Radiation - source activity
Conversion of units 26
Radioactivity
Name of unit Symbol Definition Relation to SI units
becquerel (SIunit)
Bq equiv Number of disintegrations per second = 1 Bq = 1s
curie Ci equiv 37 times 1010 Bq = 37 times 1010 Bq [32]
rutherford (H) rd equiv 1 MBq = 1 times 106 Bq
Please note that although becquerel (Bq) and hertz (Hz) both ultimately refer to the same SI base unit (sminus1) Hz isused only for periodic phenomena and Bq is only used for stochastic processes associated with radioactivity[33]
Radiation - exposure
Radiation - exposure
Name of unit Symbol Definition Relation to SI units
roentgen R 1 R equiv 258 times 10minus4 Ckg[29] = 258 times 10minus4 Ckg
The roentgen is not a SI unit and the NIST strongly discourages its continued use[34]
Radiation - absorbed dose
Radiation - absorbed dose
Name of unit Symbol Definition Relation to SI units
Name of unit Symbol Definition Relation to SI units
Roumlntgen equivalent man rem equiv 001 Sv = 001 Sv
sievert (SI unit) Sv equiv 1 Jkg[33] = 1 Sv
Although the definitions for sievert (Sv) and gray (Gy) would seem to indicate that they measure the same quantitiesthis is not the case The effect of receiving a certain dose of radiation (given as Gy) is variable and depends on manyfactors thus a new unit was needed to denote the biological effectiveness of that dose on the body this is known asthe equivalent dose and is shown in Sv The general relationship between absorbed dose and equivalent dose can berepresented as
H = Q middot D
where H is the equivalent dose D is the absorbed dose and Q is a dimensionless quality factor Thus for anyquantity of D measured in Gy the numerical value for H measured in Sv may be different[36]
Conversion of units 27
Software toolsHome and office computers come with converters in bundled spreadsheet applications or can access free convertersvia the Internet Units and measurements can be easily converted using these tools but only if the units are explicitlydefined and the conversion is compatible (eg cmHg to kPa)
Free conversion softwarebull Units (software) a popular cross-platform command-line utilitybull Converter [37] contextual unit converter for Mozilla Firefox browsersbull Converber [38] portable application converting utilitybull calculla [39] calculla - online web convertersbull iMetrix [40] - unit converter for xpbull uniteasy [41] online scientific unit conversionbull Unit Converter Add-in for Excel [42] - allow a large selection of unit conversions within the Microsoft Excel
spread sheet programbull Unit Converter [43] simple and extensible unit converterbull Portable Unit Converter [44] including 4500 units 33 unit-categories and the possibility to create custom units
General commercial sources of convertersbull Advanced electronic calculators have unit-conversion functionalitybull Spreadsheet programs usually provide conversion functions or formulas or the user can write their ownbull Commercial mathematical scientific and technical applications often include converters
See also
bull Accuracy and precisionbull English unitsbull False precisionbull Imperial unitsbull International System of Unitsbull Mesures usuellesbull Metric system
bull Natural unitsbull Roundingbull Significant figuresbull Temperature conversionbull United States customary unitsbull Units conversion by factor-labelbull Units of measurement
External linksbull British law Units of measurement regulations 1995 [45]
bull ConvertBuster [46] Variety of conversion tools to convert easilybull How Many A dictionary of units of measurement [47]
bull NIST Fundamental physical constants mdash Non-SI units [48]PDF (357 KB)bull NIST Guide to SI Units [49] Many conversion factors listedbull Online Conversion Calculators [50] Very extensive list of conversions from-to equvalent unitsbull The Unified Code for Units of Measure [51]
bull Units Symbols and Conversions XML Dictionary [52]
bull Multilingual Online Conversion of Units [53]
bull Temperature Converter [54]
Conversion of units 28
References[1] United States Naval Observatory (2009) Selected Astronomical Constants 2009 (http asa usno navy mil SecK 2009
Astronomical_Constants_2009 txt) Accessed May 10 2009[2] NIST Reference on Constants Units and Uncertainty (http physics nist gov cgi-bin cuu Valuebohrrada0|search_for=Bohr+
radius)(2006) National Institute of Standards and Technology Retrieved February 22 2008[3] National Institute of Standards and Technology General Tables of Units of Measurement (http ts nist gov WeightsAndMeasures
Publications appxc cfm)[4] Lide D (Ed) (1990) Handbook of Chemistry and Physics (71st ed) Boca Raton FL CRC Press Section 1[5] National Bureau of Standards (June 30 1959) Refinement of values for the yard and the pound Federal Register viewed September 20
2006 at National Geodetic Survey web site (http www ngs noaa gov PUBS_LIB FedRegister FRdoc59-5442 pdf)[6] The International Astronomical Union and Astronomical Units (http www iau org public_press themes measuring )[7] Klein Herbert Arthur (1988) The Science of Measurement a Historical Survey Mineola NY Dover Publications 0-4862-5839-4[8] The International System of Units Section 21 (http www bipm org en si si_brochure chapter2 2-1 ) (8 ed) Bureau International des
Poids et Mesures 2006 retrieved August 26 2009[9] International System of Units (http www bipm org en si si_brochure chapter4 table8 html) 8th ed (2006) Bureau International des
Poids et Mesures Section 41 Table 8[10] P Kenneth Seidelmann Ed (1992) Explanatory Supplement to the Astronomical Almanac Sausalito CA University Science Books p 716
and sv parsec in Glossary[11] Whitelaw Ian (2007) A Measure of All Things The Story of Man and Measurement (http books google com
booksid=3zgGEWM5-iAC) New York Macmillan 0-312-37026-1 p 152[12] De Vinne Theodore Low (1900) The practice of typography a treatise on the processes of type-making the point system the names sizes
styles and prices of plain printing types (http books google com booksid=R4-DjphIpLMC) 2nd ed New York The Century Co p142ndash150
[13] Pasko Wesley Washington (1894) American dictionary of printing and bookmaking (http books google combooksid=Z_QUAAAAIAAJ) (1894) New York Howard Lockwood p 521
[14] Rowlett Russ (2005) How Many A Dictionary of Units of Measurement (http www unc edu ~rowlett units index html)[15] Thompson A and Taylor BN (2008) Guide for the Use of the International System of Units (SI) National Institute of Standards and
Technology Special Publication 811 p 57[16] US Code of Federal Regulations Title 21 Section 1019 Paragraph (b)(5)(viii) (http ecfr gpoaccess gov cgi t text text-idxc=ecframp
rgn=div8amp view=textamp node=212 0 1 1 2 1 1 6amp idno=21) retrieved August 29 2009[17] Barry N Taylor Ed NIST Special Publication 330 The International System of Units (SI) (http physics nist gov Pubs SP330 sp330
pdf) (2001 Edition) Washington US Government Printing Office 43The 12th Conference Generale des Poids et Mesures(CGPM)hellipdeclares that the word ldquolitrerdquo may be employed as a special name for the cubic decimetre
[18] CODATA Value atomic uint of mass (http physics nist gov cgi-bin cuu Valuettme|search_for=atomic+ unit+ of+ mass) (2006)National Institute of Standards and Technology Retrieved 16 September 2008
[19] The Swiss Federal Office for Metrology gives Zentner on a German language web page (http www metas ch de scales systemch html)and quintal on the English translation of that page (http www metas ch en scales systemch html) the unit is marked speacutecifiquementsuisse
[20] Pedersen O (1983) Glossary in Coyne G Hoskin M and Pedersen O Gregorian Reform of the Calendar Proceedings of the VaticanConference to Commemorate its 400th Anniversary Vatican Observatory Available from Astrophysics Data System
[21] Richards EG (1998) Mapping Time Oxford University Press pp 94ndash95 ISBN 0-19-850413-6[22] Steel Duncan (2000) Marking Time John Wiley amp Sons p 46 ISBN 0-471-29827-1[23] CODATA Value atomic unit of force (http physics nist gov cuu Constants ) (2006) National Institute of Standards and Technology
Retrieved September 14 2008[24] [[Comiteacute International des Poids et Mesures (http www bipm org en CIPM db 1946 2 )] Resolution 2] 1946 retrieved August 26
2009[25] Barry N Taylor (April 1995) Guide for the Use of the International System of Units (SI) (http physics nist gov cuu pdf sp811 pdf)
(NIST Special Publication 811) Washington DC US Government Printing Office pp 57ndash68[26] Barry N Taylor (April 1995) Guide for the Use of the International System of Units (SI) (NIST Special Publication 811) Washington DC
US Government Printing Office p 5[27] International System of Units (http www bipm org en si si_brochure chapter4 table7 html) 8th ed (2006) Bureau International des
Poids et Mesures Section 41 Table 7[28] The NIST Reference on Constants Units and Uncertainty (http physics nist gov cgi-bin cuu Valueauedm) 2006 retrieved August
26 2009[29] NIST Guide to SI Units Appendix B9 (http physics nist gov Pubs SP811 appenB9 html) retrieved August 27 2009[30] Standard for the Use of the International System of Units (SI) The Modern Metric System IEEEASTM SI 10-1997 (1997) New York and
West Conshohocken PA Institute of Electrical and Electronics Engineers and American Society for Testing and Materials Tables A1through A5
Conversion of units 29
[31] The NIST Reference on Constants Units and Uncertainty (http physics nist gov cuu Units candela html) retrieved August 28 2009[32] Ambler Thompson amp Barry N Taylor (2008) Guide for the Use of the International System of Units (SI) (http physics nist gov cuu
pdf sp811 pdf) Special Publication 811 Gaithersburg MD National Institute of Standards and Technology p 10[33] The International System of Units Section 222 Table 3 (http www bipm org en si si_brochure chapter2 2-2 table3 html) (8 ed)
Bureau International des Poids et Mesures 2006 retrieved August 27 2009[34] The NIST Guide to the SI (Special Publication 811) section 52 (http physics nist gov Pubs SP811 sec05 html5 2) 2008 retrieved
August 27 2009[35] Ambler Thompson amp Barry N Taylor (2008) Guide for the Use of the International System of Units (SI) (http physics nist gov cuu
pdf sp811 pdf) Special Publication 811 Gaithersburg MD National Institute of Standards and Technology p 5[36] [[Comiteacute international des poids et mesures (http www bipm org en CIPM db 2002 2 )] 2002 Recommendation 2] retrieved
August 27 2009[37] http converter mozdev org[38] http www xyntec com converber htm[39] http www calculla com[40] http illusions hu index phptask=100amp lang=0amp statpage=86[41] http www uniteasy com[42] http www tenderwire com wikipedialandingpage[43] http www kamlex com index phpoption=com_contentamp view=articleamp id=53amp Itemid=55[44] http www sttmedia com unitconverter[45] http www hmso gov uk si si1995 Uksi_19951804_en_2 htm[46] http www convertbuster com[47] http www unc edu ~rowlett units[48] http physics nist gov cuu Document nonsi_in_1998 pdf[49] http physics nist gov Pubs SP811 appenB9 html[50] http www onlineconversion com[51] http aurora rg iupui edu ~schadow units UCUM ucum html[52] http www posc org refs poscUnits20 xml[53] http www imperialtometric com[54] http www tampile com
Article Sources and Contributors 30
Article Sources and ContributorsConversion of units Source httpenwikipediaorgwindexphpoldid=373975089 Contributors 1571781xxx 7 A-giau AVSI Acather96 Ahoerstemeier Alexius08 Altenmann AndreEngels Andrewa Andy120290 Anonymi Ariconte Army1987 ArnoldReinhold Arthur3030 Aspects AxelBoldt AzaToth Azikala BW95 Bdesham Beland Bensaccount Bkumartvm Blackand White BlaiseFEgan BlueEarth Bobblewik Borbrav Bpmullins Bryan Derksen C J B Scholten CORNELIUSSEON CTZMSC3 Calltech Camerajohn Chaosfeary Charles MatthewsChris the speller Cmdrjameson Colonies Chris Conversion script Cope555 Crappy13 Crissov CyrilB DARTH SIDIOUS 2 DMacks DanielCD Dark Formal DarkestSideX DekisugiDenelson83 Dhp1080 Dicklyon DirkvdM Donald Duck Donarreiskoffer Dramatic Dyss DAringsbquougosz Egil Ehrenkater Ejohnsonboulder Elexmax Elf Emokhberi Enon Eob Epbr123Euchiasmus Fathead99 Father Goose Fella22 Femto FernandoAC Fibula Flutefreek Fred Bauder Fredrik Fuhghettaboutit Fuzheado Gaff Gene Nygaard Georgiy1996 Gerry AshtonGiftlite Gilliam Glenn L GoingBatty Goobergunch Gregsexton Greyengine5 Grunt Gurch Gutza HLHJ Haemo Hammersbach Heracles31 Herbee Heron HikerBush Hqb IcairnsIgiffin Indefatigable Isis JBobbitt JHunterJ Jabowery JakeVortex Jamicanmonkey Jason Begin Jay Jc3s5h Jcronen1 Jdoherty Jeffz1 Jeronimo Jimmuhk Jimp Jimwilliams57 JoeinwapJohndburger Josh Parris Jq4bagiq Kaihsu KaneWang Keenan Pepper Kevin Rector KeyStorm Khukri Kurtan Lee Daniel Crocker LightYear Linuxoidoz Liv4christ210 Loggie Lolo252Lupinelawyer M ichaeligl MJCdetroit MTC Mac MacMcF Magore Markus Kuhn Masterqwe MaxHund Maxamegalon2000 Mbeychok Meggar Mh26 Michael Daly Michael Hardy MichelAudy Mikelifeguard Mikhailov Kusserow Mindbuilder Missvain Monger Mr bulow MrOllie MrZhuKeeper Muro de Aguas Mwanner Mwtoews Nandesuka Natkeeran Ndsg NgjaimeNhy67ygv Nick Y Nick123 NickPenguin Ninjagecko Noe Nosilleg Now3r3 Obelix homologator Oldadamml Oleg Alexandrov Olivier Ortolan88 OwenBlacker Pac72 PassargeaPatrick Paul Martin Peter Horn Physchim62 Piels Pierdm Pmanderson Prometheus235 Quadell QuantumEleven Quod erat demonstrandum 314159 Radagast83 Rccoms RedWolfReinyday Revipm Rexparry sydney Reyk Rhetth Rhialto Rich Farmbrough Richard Myers Rjwilmsi Rlsheehan Robin Barry RoySmith Rpwolfgram SD6-Agent SGBailey SamuelLowry Samw Sander123 Seabhcan SebastianHelm Sherbert1 Shinhan Shrew Sietse Snel SimonP Sinbaddasail0r Skotte Smalljim SomeHuman Spencer Srleffler StarwarsmastergeekSteacoon StefanK SteveRamone Stevertigo Stokerm Suisui Sunev Superboy112233 Superm401 Synchronism Tacoman1996 Tarquin Taw Teratornis The Man in Question ThierrycThingg Thinking of England Thunderbird2 Timwi Tobias Hoevekamp Tomasr Tonsofpcs Toon05 Topsykretts2512 Trekphiler Tuwile Twanvl Uday147502 Unitman00 UrhixidurUtherSRG Vargenau Vsmith WarrenPlatts Wasell Welsh Whispering Wikinger Wolfkeeper Wtmitchell XJamRastafire Xenonice Yath Zginder Zibem Zocky Zotel 713 anonymousedits
mach number M Ratio of the speed to the speed of sound in the medium Varies especially with temperatureAbout 761 mph (1225 kph) in air at sea level to about 660 mph (1062 kph) at jet altitudesUnitless
asymp 340 to 295 ms foraircraft
metre per second(SI unit)
ms equiv 1 ms = 1 ms
mile per hour mph equiv 1 mih = 0447 04 ms
mile per minute mpm equiv 1 mimin = 268224 ms
mile per second mps equiv 1 mis = 1 609344 ms
speed of light invacuum
c equiv 299 792 458 ms = 299 792 458 ms
speed of sound inair
s Varies especially with temperature About 761 mph (1225 kph) in air at sea level to about660 mph (1062 kph) at jet altitudes
asymp 340 to 295 ms ataircraft altitudes
A velocity consists of a speed combined with a direction the speed part of the velocity takes units of speed
Conversion of units 15
Flow (volume)
Flow
Name of unit Symbol Definition Relation to SI units
cubic foot per minute CFM equiv 1 ft3min = 4719474432 times 10minus4 m3s
cubic foot per second ft3s equiv 1 ft3s = 0028316846592 m3s
cubic inch per minute in3min equiv 1 in3min = 27311773 times 10minus7 m3s
cubic inch per second in3s equiv 1 in3s = 16387064 times 10minus5 m3s
cubic metre per second (SIunit)
m3s equiv 1 m3s = 1 m3s
gallon (US fluid) per day GPD equiv 1 gald = 4381263638 times 10minus8 m3s
gallon (US fluid) per hour GPH equiv 1 galh = 1051503273 times 10minus6 m3s
gallon (US fluid) per minute GPM equiv 1 galmin = 630901964 times 10minus5 m3s
litre per minute LPM equiv 1 Lmin = 16 times 10minus5 m3s
Acceleration
Acceleration
Name of unit Symbol Definition Relation to SI units
foot per hour per second fphs equiv 1 ft(hmiddots) asymp 8466 667 times 10minus5
ms2
foot per minute per second fpms equiv 1 ft(minmiddots) = 508 times 10minus3 ms2
foot per second squared fps2 equiv 1 fts2 = 3048 times 10minus1 ms2
gal galileo Gal equiv 1 cms2 = 10minus2 ms2
inch per minute per second ipms equiv 1 in(minmiddots) asymp 4233 333 times 10minus4
ms2
inch per second squared ips2 equiv 1 ins2 = 254 times 10minus2 ms2
knot per second kns equiv 1 kns asymp 5144 444 times 10minus1
ms2
metre per second squared (SI unit) ms2 equiv 1 ms2 = 1 ms2
mile per hour per second mphs equiv 1 mi(hmiddots) = 44704 times 10minus1 ms2
mile per minute per second mpms equiv 1 mi(minmiddots) = 268224 ms2
mile per second squared mps2 equiv 1 mis2 = 1609 344 times 103 ms2
standard gravity g equiv 9806 65 ms2 = 9806 65 ms2
Conversion of units 16
Force
Force
Name of unit Symbol Definition Relation to SI units
atomic unit of force equiv memiddotα2middotc2a0 asymp 8238 722 06 times 10minus8 N
[23]
dyne (cgs unit) dyn equiv gmiddotcms2 = 10minus5 N
kilogram-force kilopondgrave-force
kgf kp Gf equiv g times 1 kg = 9806 65 N
kip kip-force kip kipfklbf
equiv g times 1 000 lb = 4448 221 6152605 times 103 N
milligrave-force gravet-force mGf gf equiv g times 1 g = 9806 65 mN
newton (SI unit) N A force capable of giving a mass of one kg an acceleration of one metreper second per second[24]
= 1 N = 1 kgmiddotms2
ounce-force ozf equiv g times 1 oz = 0278 013 850 9537812 N
pound lb equiv slugmiddotfts2 = 4448 230 531 N
pound-force lbf equiv g times 1 lb = 4448 221 615 2605 N
poise (cgs unit) P equiv 10minus1 Pamiddots = 01 Pamiddots
pound per foot hour lb(ftmiddoth) equiv 1 lb(ftmiddoth) asymp 4133 789 times 10minus4 Pamiddots
pound per foot second lb(ftmiddots) equiv 1 lb(ftmiddots) asymp 1488164 Pamiddots
pound-force second per square foot lbfmiddotsft2 equiv 1 lbfmiddotsft2 asymp 4788026 Pamiddots
pound-force second per square inch lbfmiddotsin2 equiv 1 lbfmiddotsin2 asymp 6894757 Pamiddots
Conversion of units 21
Kinematic viscosity
Kinematic viscosity
Name of unit Symbol Definition Relation to SI units
square foot per second ft2s equiv 1 ft2s = 009290304 m2s
square metre per second (SI unit) m2s equiv 1 m2s = 1 m2s
stokes (cgs unit) St equiv10minus4 m2s
= 10minus4 m2s
Electric current
Electric current
Name of unit Symbol Definition Relation to SI units
ampere (SI base unit) A equiv The constant current needed to produce a force of 2 times 10minus7 newton per metre betweentwo straight parallel conductors of infinite length and negligible circular cross-sectionplaced one metre apart in a vacuum[8]
= 1 A
electromagnetic unitabampere (cgs unit)
abamp equiv 10 A = 10 A
esu per secondstatampere (cgs unit)
esus equiv (01 Amiddotms) c asymp3335641 times 10minus10 A
Electric charge
Electric charge
Name of unit Symbol Definition Relation to SI units
abcoulomb electromagnetic unit (cgsunit)
abC emu equiv 10 C = 10 C
atomic unit of charge au equiv e asymp 1602 176462 times 10minus19 C
coulomb (SI unit) C equiv The amount of electricity carried in one second of time by oneampere of current[24]
= 1 C = 1 Amiddots
faraday F equiv 1 mol times NAmiddote asymp 96 4853383 C
statcoulomb franklin electrostatic unit(cgs unit)
statC Fresu
equiv (01 Amiddotm) c asymp 3335 641 times 10minus10 C
Conversion of units 22
Electric dipole
Electric dipole
Name of unit Symbol Definition Relation to SI units
atomic unit of electric dipole moment ea0 asymp 8478 352 81 times 10minus30
Cmiddotm[28]
Electromotive force electric potential difference
Voltage electromotive force
Name ofunit
Symbol Definition Relation to SI units
abvolt (cgsunit)
abV equiv 1 times 10minus8 V = 1 times 10minus8 V
statvolt (cgsunit)
statV equiv cmiddot (1 μJAmiddotm) = 299792 458 V
volt (SIunit)
V The difference in electric potential across two points along a conducting wire carrying one ampereof constant current when the power dissipated between the points equals one watt[24]
= 1 V = 1 WA = 1kgmiddotm2(Amiddots3)
Electrical resistance
Electrical resistance
Name ofunit
Symbol Definition Relation to SI units
ohm (SIunit)
Ω The resistance between two points in a conductor when one volt of electric potential differenceapplied to these points produces one ampere of current in the conductor[24]
= 1 Ω = 1 VA = 1kgmiddotm2(A2middots3)
Capacitance
Capacitors ability to store charge
Name ofunit
Symbol Definition Relation to SI units
farad (SIunit)
F The capacitance between two parallel plates that results in one volt of potential difference whencharged by one coulomb of electricity[24]
= 1 F = 1 CV = 1A2middots4(kgmiddotm2)
Conversion of units 23
Magnetic flux
magnetic flux
Name of unit Symbol Definition Relation to SI units
maxwell (CGSunit)
Mx equiv 10minus8 Wb[29] = 1 times 10minus8 Wb
weber (SIunit)
Wb Magnetic flux which linking a circuit of one turn would produce in it an electromotive force of1 volt if it were reduced to zero at a uniform rate in 1 second[24]
= 1 Wb = 1 Vmiddots = 1kgmiddotm2(Amiddots2)
Magnetic flux density
What physicists call Magnetic field is called Magnetic flux density by electrical engineersand magnetic induction by applied mathematicians and electrical engineers
Name of unit Symbol Definition Relation to SI units
gauss (CGS unit) G equiv Mxcm2 = 10minus4
T= 1 times 10minus4 T [30]
tesla (SI unit) T equiv Wbm2 = 1 T = 1 Wbm2 = 1kg(Amiddots2)
Inductance
Inductance
Name ofunit
Symbol Definition Relation to SI units
henry (SIunit)
H The inductance of a closed circuit that produces one volt of electromotive force when the current inthe circuit varies at a uniform rate of one ampere per second[24]
= 1 H = 1 WbA = 1kgmiddotm2(Amiddots)2
Temperature
Temperature
Name of unit Symbol Definition Conversion to kelvin
degree Celsius degC degC equiv K minus 27315 [K] equiv [degC] + 27315
degree Delisle degDe [K] = 37315 minus [degDe] times 23
degree Fahrenheit degF degF equiv degC times 95 + 32 [K] equiv ([degF] + 45967) times 59
degree Newton degN [K] = [degN] times 10033 + 27315
degree Rankine degR degRa degR equiv K times 95 [K] equiv [degR] times 59
degree Reacuteaumur degReacute [K] = [degReacute] times 54 + 27315
degree Roslashmer degRoslash [K] = ([degRoslash] minus 75) times 4021 + 27315
kelvin (SI baseunit)
K equiv 127316 of the thermodynamic temperature of the triple point of water[8] equiv 1 K
Conversion of units 24
Information entropy
Information entropy
Name of unit Symbol Definition Relation to SI units Relation to bits
SI unit JK equiv JK = 1 JK
nat nip nepit nat equiv kB = 1380 650 5(23) times 10minus23 JK
bit shannon bit b Sh equiv ln(2) times kB = 9569 940 (16) times 10minus24 JK = 1 bit
ban hartley ban Hart equiv ln(10) times kB = 3179 065 3(53) times 10minus23 JK
nibble equiv 4 bits = 3827 976 0(64) times 10minus23 JK = 22 bit
byte B equiv 8 bits = 7655 952 (13) times 10minus23 JK = 23 bit
kilobyte (decimal) kB equiv 1 000 B = 7655 952 (13) times 10minus20 JK
kilobyte (kibibyte) KB KiB equiv 1 024 B = 7839 695 (13) times 10minus20 JK = 210 bit
Often information entropy is measured in shannons whereas the (discrete) storage space of digital devices ismeasured in bits Thus uncompressed redundant data occupy more than one bit of storage per shannon ofinformation entropy The multiples of a bit listed above are usually used with this meaning Other times the bit isused as a measure of information entropy and is thus a synonym of shannon
Luminous intensityThe candela is the preferred nomenclature for the SI unit
Luminous intensity
Name of unit Symbol Definition Relation toSI units
candela (SI baseunit) candle
cd The luminous intensity in a given direction of a source that emits monochromatic radiation offrequency 540 times 1012 hertz and that has a radiant intensity in that direction of 1683 watt persteradian[8]
= 1 cd
candlepower (new) cp equiv cd The use of candlepower as a unit is discouraged due to its ambiguity = 1 cd
candlepower (oldpre-1948)
cp Varies and is poorly reproducible[31] Approximately 0981 cd[14] asymp 0981 cd
Luminance
Conversion of units 25
Luminance
Name of unit Symbol Definition Relation to SI units
candela per square foot cdft2 equiv cdft2 asymp10763910417 cdm2
candela per square inch cdin2 equiv cdin2 asymp 15500031 cdm2
candela per square metre (SI unit) nit (deprecated[14] ) cdm2 equiv cdm2 = 1 cdm2
Name of unit Symbol Definition Relation to SI units
lumen (SIunit)
lm equiv cdmiddotsr = 1 lm = 1 cdmiddotsr
Illuminance
Illuminance
Name of unit Symbol Definition Relation to SI units
footcandle lumen per square foot fc equiv lmft2 = 10763910417 lx
lumen per square inch lmin2 equiv lmin2 asymp 15500031 lx
lux (SI unit) lx equiv lmm2 = 1 lx = 1 lmm2
phot (CGS unit) ph equiv lmcm2 = 1 times 104 lx
Radiation - source activity
Conversion of units 26
Radioactivity
Name of unit Symbol Definition Relation to SI units
becquerel (SIunit)
Bq equiv Number of disintegrations per second = 1 Bq = 1s
curie Ci equiv 37 times 1010 Bq = 37 times 1010 Bq [32]
rutherford (H) rd equiv 1 MBq = 1 times 106 Bq
Please note that although becquerel (Bq) and hertz (Hz) both ultimately refer to the same SI base unit (sminus1) Hz isused only for periodic phenomena and Bq is only used for stochastic processes associated with radioactivity[33]
Radiation - exposure
Radiation - exposure
Name of unit Symbol Definition Relation to SI units
roentgen R 1 R equiv 258 times 10minus4 Ckg[29] = 258 times 10minus4 Ckg
The roentgen is not a SI unit and the NIST strongly discourages its continued use[34]
Radiation - absorbed dose
Radiation - absorbed dose
Name of unit Symbol Definition Relation to SI units
Name of unit Symbol Definition Relation to SI units
Roumlntgen equivalent man rem equiv 001 Sv = 001 Sv
sievert (SI unit) Sv equiv 1 Jkg[33] = 1 Sv
Although the definitions for sievert (Sv) and gray (Gy) would seem to indicate that they measure the same quantitiesthis is not the case The effect of receiving a certain dose of radiation (given as Gy) is variable and depends on manyfactors thus a new unit was needed to denote the biological effectiveness of that dose on the body this is known asthe equivalent dose and is shown in Sv The general relationship between absorbed dose and equivalent dose can berepresented as
H = Q middot D
where H is the equivalent dose D is the absorbed dose and Q is a dimensionless quality factor Thus for anyquantity of D measured in Gy the numerical value for H measured in Sv may be different[36]
Conversion of units 27
Software toolsHome and office computers come with converters in bundled spreadsheet applications or can access free convertersvia the Internet Units and measurements can be easily converted using these tools but only if the units are explicitlydefined and the conversion is compatible (eg cmHg to kPa)
Free conversion softwarebull Units (software) a popular cross-platform command-line utilitybull Converter [37] contextual unit converter for Mozilla Firefox browsersbull Converber [38] portable application converting utilitybull calculla [39] calculla - online web convertersbull iMetrix [40] - unit converter for xpbull uniteasy [41] online scientific unit conversionbull Unit Converter Add-in for Excel [42] - allow a large selection of unit conversions within the Microsoft Excel
spread sheet programbull Unit Converter [43] simple and extensible unit converterbull Portable Unit Converter [44] including 4500 units 33 unit-categories and the possibility to create custom units
General commercial sources of convertersbull Advanced electronic calculators have unit-conversion functionalitybull Spreadsheet programs usually provide conversion functions or formulas or the user can write their ownbull Commercial mathematical scientific and technical applications often include converters
See also
bull Accuracy and precisionbull English unitsbull False precisionbull Imperial unitsbull International System of Unitsbull Mesures usuellesbull Metric system
bull Natural unitsbull Roundingbull Significant figuresbull Temperature conversionbull United States customary unitsbull Units conversion by factor-labelbull Units of measurement
External linksbull British law Units of measurement regulations 1995 [45]
bull ConvertBuster [46] Variety of conversion tools to convert easilybull How Many A dictionary of units of measurement [47]
bull NIST Fundamental physical constants mdash Non-SI units [48]PDF (357 KB)bull NIST Guide to SI Units [49] Many conversion factors listedbull Online Conversion Calculators [50] Very extensive list of conversions from-to equvalent unitsbull The Unified Code for Units of Measure [51]
bull Units Symbols and Conversions XML Dictionary [52]
bull Multilingual Online Conversion of Units [53]
bull Temperature Converter [54]
Conversion of units 28
References[1] United States Naval Observatory (2009) Selected Astronomical Constants 2009 (http asa usno navy mil SecK 2009
Astronomical_Constants_2009 txt) Accessed May 10 2009[2] NIST Reference on Constants Units and Uncertainty (http physics nist gov cgi-bin cuu Valuebohrrada0|search_for=Bohr+
radius)(2006) National Institute of Standards and Technology Retrieved February 22 2008[3] National Institute of Standards and Technology General Tables of Units of Measurement (http ts nist gov WeightsAndMeasures
Publications appxc cfm)[4] Lide D (Ed) (1990) Handbook of Chemistry and Physics (71st ed) Boca Raton FL CRC Press Section 1[5] National Bureau of Standards (June 30 1959) Refinement of values for the yard and the pound Federal Register viewed September 20
2006 at National Geodetic Survey web site (http www ngs noaa gov PUBS_LIB FedRegister FRdoc59-5442 pdf)[6] The International Astronomical Union and Astronomical Units (http www iau org public_press themes measuring )[7] Klein Herbert Arthur (1988) The Science of Measurement a Historical Survey Mineola NY Dover Publications 0-4862-5839-4[8] The International System of Units Section 21 (http www bipm org en si si_brochure chapter2 2-1 ) (8 ed) Bureau International des
Poids et Mesures 2006 retrieved August 26 2009[9] International System of Units (http www bipm org en si si_brochure chapter4 table8 html) 8th ed (2006) Bureau International des
Poids et Mesures Section 41 Table 8[10] P Kenneth Seidelmann Ed (1992) Explanatory Supplement to the Astronomical Almanac Sausalito CA University Science Books p 716
and sv parsec in Glossary[11] Whitelaw Ian (2007) A Measure of All Things The Story of Man and Measurement (http books google com
booksid=3zgGEWM5-iAC) New York Macmillan 0-312-37026-1 p 152[12] De Vinne Theodore Low (1900) The practice of typography a treatise on the processes of type-making the point system the names sizes
styles and prices of plain printing types (http books google com booksid=R4-DjphIpLMC) 2nd ed New York The Century Co p142ndash150
[13] Pasko Wesley Washington (1894) American dictionary of printing and bookmaking (http books google combooksid=Z_QUAAAAIAAJ) (1894) New York Howard Lockwood p 521
[14] Rowlett Russ (2005) How Many A Dictionary of Units of Measurement (http www unc edu ~rowlett units index html)[15] Thompson A and Taylor BN (2008) Guide for the Use of the International System of Units (SI) National Institute of Standards and
Technology Special Publication 811 p 57[16] US Code of Federal Regulations Title 21 Section 1019 Paragraph (b)(5)(viii) (http ecfr gpoaccess gov cgi t text text-idxc=ecframp
rgn=div8amp view=textamp node=212 0 1 1 2 1 1 6amp idno=21) retrieved August 29 2009[17] Barry N Taylor Ed NIST Special Publication 330 The International System of Units (SI) (http physics nist gov Pubs SP330 sp330
pdf) (2001 Edition) Washington US Government Printing Office 43The 12th Conference Generale des Poids et Mesures(CGPM)hellipdeclares that the word ldquolitrerdquo may be employed as a special name for the cubic decimetre
[18] CODATA Value atomic uint of mass (http physics nist gov cgi-bin cuu Valuettme|search_for=atomic+ unit+ of+ mass) (2006)National Institute of Standards and Technology Retrieved 16 September 2008
[19] The Swiss Federal Office for Metrology gives Zentner on a German language web page (http www metas ch de scales systemch html)and quintal on the English translation of that page (http www metas ch en scales systemch html) the unit is marked speacutecifiquementsuisse
[20] Pedersen O (1983) Glossary in Coyne G Hoskin M and Pedersen O Gregorian Reform of the Calendar Proceedings of the VaticanConference to Commemorate its 400th Anniversary Vatican Observatory Available from Astrophysics Data System
[21] Richards EG (1998) Mapping Time Oxford University Press pp 94ndash95 ISBN 0-19-850413-6[22] Steel Duncan (2000) Marking Time John Wiley amp Sons p 46 ISBN 0-471-29827-1[23] CODATA Value atomic unit of force (http physics nist gov cuu Constants ) (2006) National Institute of Standards and Technology
Retrieved September 14 2008[24] [[Comiteacute International des Poids et Mesures (http www bipm org en CIPM db 1946 2 )] Resolution 2] 1946 retrieved August 26
2009[25] Barry N Taylor (April 1995) Guide for the Use of the International System of Units (SI) (http physics nist gov cuu pdf sp811 pdf)
(NIST Special Publication 811) Washington DC US Government Printing Office pp 57ndash68[26] Barry N Taylor (April 1995) Guide for the Use of the International System of Units (SI) (NIST Special Publication 811) Washington DC
US Government Printing Office p 5[27] International System of Units (http www bipm org en si si_brochure chapter4 table7 html) 8th ed (2006) Bureau International des
Poids et Mesures Section 41 Table 7[28] The NIST Reference on Constants Units and Uncertainty (http physics nist gov cgi-bin cuu Valueauedm) 2006 retrieved August
26 2009[29] NIST Guide to SI Units Appendix B9 (http physics nist gov Pubs SP811 appenB9 html) retrieved August 27 2009[30] Standard for the Use of the International System of Units (SI) The Modern Metric System IEEEASTM SI 10-1997 (1997) New York and
West Conshohocken PA Institute of Electrical and Electronics Engineers and American Society for Testing and Materials Tables A1through A5
Conversion of units 29
[31] The NIST Reference on Constants Units and Uncertainty (http physics nist gov cuu Units candela html) retrieved August 28 2009[32] Ambler Thompson amp Barry N Taylor (2008) Guide for the Use of the International System of Units (SI) (http physics nist gov cuu
pdf sp811 pdf) Special Publication 811 Gaithersburg MD National Institute of Standards and Technology p 10[33] The International System of Units Section 222 Table 3 (http www bipm org en si si_brochure chapter2 2-2 table3 html) (8 ed)
Bureau International des Poids et Mesures 2006 retrieved August 27 2009[34] The NIST Guide to the SI (Special Publication 811) section 52 (http physics nist gov Pubs SP811 sec05 html5 2) 2008 retrieved
August 27 2009[35] Ambler Thompson amp Barry N Taylor (2008) Guide for the Use of the International System of Units (SI) (http physics nist gov cuu
pdf sp811 pdf) Special Publication 811 Gaithersburg MD National Institute of Standards and Technology p 5[36] [[Comiteacute international des poids et mesures (http www bipm org en CIPM db 2002 2 )] 2002 Recommendation 2] retrieved
August 27 2009[37] http converter mozdev org[38] http www xyntec com converber htm[39] http www calculla com[40] http illusions hu index phptask=100amp lang=0amp statpage=86[41] http www uniteasy com[42] http www tenderwire com wikipedialandingpage[43] http www kamlex com index phpoption=com_contentamp view=articleamp id=53amp Itemid=55[44] http www sttmedia com unitconverter[45] http www hmso gov uk si si1995 Uksi_19951804_en_2 htm[46] http www convertbuster com[47] http www unc edu ~rowlett units[48] http physics nist gov cuu Document nonsi_in_1998 pdf[49] http physics nist gov Pubs SP811 appenB9 html[50] http www onlineconversion com[51] http aurora rg iupui edu ~schadow units UCUM ucum html[52] http www posc org refs poscUnits20 xml[53] http www imperialtometric com[54] http www tampile com
Article Sources and Contributors 30
Article Sources and ContributorsConversion of units Source httpenwikipediaorgwindexphpoldid=373975089 Contributors 1571781xxx 7 A-giau AVSI Acather96 Ahoerstemeier Alexius08 Altenmann AndreEngels Andrewa Andy120290 Anonymi Ariconte Army1987 ArnoldReinhold Arthur3030 Aspects AxelBoldt AzaToth Azikala BW95 Bdesham Beland Bensaccount Bkumartvm Blackand White BlaiseFEgan BlueEarth Bobblewik Borbrav Bpmullins Bryan Derksen C J B Scholten CORNELIUSSEON CTZMSC3 Calltech Camerajohn Chaosfeary Charles MatthewsChris the speller Cmdrjameson Colonies Chris Conversion script Cope555 Crappy13 Crissov CyrilB DARTH SIDIOUS 2 DMacks DanielCD Dark Formal DarkestSideX DekisugiDenelson83 Dhp1080 Dicklyon DirkvdM Donald Duck Donarreiskoffer Dramatic Dyss DAringsbquougosz Egil Ehrenkater Ejohnsonboulder Elexmax Elf Emokhberi Enon Eob Epbr123Euchiasmus Fathead99 Father Goose Fella22 Femto FernandoAC Fibula Flutefreek Fred Bauder Fredrik Fuhghettaboutit Fuzheado Gaff Gene Nygaard Georgiy1996 Gerry AshtonGiftlite Gilliam Glenn L GoingBatty Goobergunch Gregsexton Greyengine5 Grunt Gurch Gutza HLHJ Haemo Hammersbach Heracles31 Herbee Heron HikerBush Hqb IcairnsIgiffin Indefatigable Isis JBobbitt JHunterJ Jabowery JakeVortex Jamicanmonkey Jason Begin Jay Jc3s5h Jcronen1 Jdoherty Jeffz1 Jeronimo Jimmuhk Jimp Jimwilliams57 JoeinwapJohndburger Josh Parris Jq4bagiq Kaihsu KaneWang Keenan Pepper Kevin Rector KeyStorm Khukri Kurtan Lee Daniel Crocker LightYear Linuxoidoz Liv4christ210 Loggie Lolo252Lupinelawyer M ichaeligl MJCdetroit MTC Mac MacMcF Magore Markus Kuhn Masterqwe MaxHund Maxamegalon2000 Mbeychok Meggar Mh26 Michael Daly Michael Hardy MichelAudy Mikelifeguard Mikhailov Kusserow Mindbuilder Missvain Monger Mr bulow MrOllie MrZhuKeeper Muro de Aguas Mwanner Mwtoews Nandesuka Natkeeran Ndsg NgjaimeNhy67ygv Nick Y Nick123 NickPenguin Ninjagecko Noe Nosilleg Now3r3 Obelix homologator Oldadamml Oleg Alexandrov Olivier Ortolan88 OwenBlacker Pac72 PassargeaPatrick Paul Martin Peter Horn Physchim62 Piels Pierdm Pmanderson Prometheus235 Quadell QuantumEleven Quod erat demonstrandum 314159 Radagast83 Rccoms RedWolfReinyday Revipm Rexparry sydney Reyk Rhetth Rhialto Rich Farmbrough Richard Myers Rjwilmsi Rlsheehan Robin Barry RoySmith Rpwolfgram SD6-Agent SGBailey SamuelLowry Samw Sander123 Seabhcan SebastianHelm Sherbert1 Shinhan Shrew Sietse Snel SimonP Sinbaddasail0r Skotte Smalljim SomeHuman Spencer Srleffler StarwarsmastergeekSteacoon StefanK SteveRamone Stevertigo Stokerm Suisui Sunev Superboy112233 Superm401 Synchronism Tacoman1996 Tarquin Taw Teratornis The Man in Question ThierrycThingg Thinking of England Thunderbird2 Timwi Tobias Hoevekamp Tomasr Tonsofpcs Toon05 Topsykretts2512 Trekphiler Tuwile Twanvl Uday147502 Unitman00 UrhixidurUtherSRG Vargenau Vsmith WarrenPlatts Wasell Welsh Whispering Wikinger Wolfkeeper Wtmitchell XJamRastafire Xenonice Yath Zginder Zibem Zocky Zotel 713 anonymousedits
poise (cgs unit) P equiv 10minus1 Pamiddots = 01 Pamiddots
pound per foot hour lb(ftmiddoth) equiv 1 lb(ftmiddoth) asymp 4133 789 times 10minus4 Pamiddots
pound per foot second lb(ftmiddots) equiv 1 lb(ftmiddots) asymp 1488164 Pamiddots
pound-force second per square foot lbfmiddotsft2 equiv 1 lbfmiddotsft2 asymp 4788026 Pamiddots
pound-force second per square inch lbfmiddotsin2 equiv 1 lbfmiddotsin2 asymp 6894757 Pamiddots
Conversion of units 21
Kinematic viscosity
Kinematic viscosity
Name of unit Symbol Definition Relation to SI units
square foot per second ft2s equiv 1 ft2s = 009290304 m2s
square metre per second (SI unit) m2s equiv 1 m2s = 1 m2s
stokes (cgs unit) St equiv10minus4 m2s
= 10minus4 m2s
Electric current
Electric current
Name of unit Symbol Definition Relation to SI units
ampere (SI base unit) A equiv The constant current needed to produce a force of 2 times 10minus7 newton per metre betweentwo straight parallel conductors of infinite length and negligible circular cross-sectionplaced one metre apart in a vacuum[8]
= 1 A
electromagnetic unitabampere (cgs unit)
abamp equiv 10 A = 10 A
esu per secondstatampere (cgs unit)
esus equiv (01 Amiddotms) c asymp3335641 times 10minus10 A
Electric charge
Electric charge
Name of unit Symbol Definition Relation to SI units
abcoulomb electromagnetic unit (cgsunit)
abC emu equiv 10 C = 10 C
atomic unit of charge au equiv e asymp 1602 176462 times 10minus19 C
coulomb (SI unit) C equiv The amount of electricity carried in one second of time by oneampere of current[24]
= 1 C = 1 Amiddots
faraday F equiv 1 mol times NAmiddote asymp 96 4853383 C
statcoulomb franklin electrostatic unit(cgs unit)
statC Fresu
equiv (01 Amiddotm) c asymp 3335 641 times 10minus10 C
Conversion of units 22
Electric dipole
Electric dipole
Name of unit Symbol Definition Relation to SI units
atomic unit of electric dipole moment ea0 asymp 8478 352 81 times 10minus30
Cmiddotm[28]
Electromotive force electric potential difference
Voltage electromotive force
Name ofunit
Symbol Definition Relation to SI units
abvolt (cgsunit)
abV equiv 1 times 10minus8 V = 1 times 10minus8 V
statvolt (cgsunit)
statV equiv cmiddot (1 μJAmiddotm) = 299792 458 V
volt (SIunit)
V The difference in electric potential across two points along a conducting wire carrying one ampereof constant current when the power dissipated between the points equals one watt[24]
= 1 V = 1 WA = 1kgmiddotm2(Amiddots3)
Electrical resistance
Electrical resistance
Name ofunit
Symbol Definition Relation to SI units
ohm (SIunit)
Ω The resistance between two points in a conductor when one volt of electric potential differenceapplied to these points produces one ampere of current in the conductor[24]
= 1 Ω = 1 VA = 1kgmiddotm2(A2middots3)
Capacitance
Capacitors ability to store charge
Name ofunit
Symbol Definition Relation to SI units
farad (SIunit)
F The capacitance between two parallel plates that results in one volt of potential difference whencharged by one coulomb of electricity[24]
= 1 F = 1 CV = 1A2middots4(kgmiddotm2)
Conversion of units 23
Magnetic flux
magnetic flux
Name of unit Symbol Definition Relation to SI units
maxwell (CGSunit)
Mx equiv 10minus8 Wb[29] = 1 times 10minus8 Wb
weber (SIunit)
Wb Magnetic flux which linking a circuit of one turn would produce in it an electromotive force of1 volt if it were reduced to zero at a uniform rate in 1 second[24]
= 1 Wb = 1 Vmiddots = 1kgmiddotm2(Amiddots2)
Magnetic flux density
What physicists call Magnetic field is called Magnetic flux density by electrical engineersand magnetic induction by applied mathematicians and electrical engineers
Name of unit Symbol Definition Relation to SI units
gauss (CGS unit) G equiv Mxcm2 = 10minus4
T= 1 times 10minus4 T [30]
tesla (SI unit) T equiv Wbm2 = 1 T = 1 Wbm2 = 1kg(Amiddots2)
Inductance
Inductance
Name ofunit
Symbol Definition Relation to SI units
henry (SIunit)
H The inductance of a closed circuit that produces one volt of electromotive force when the current inthe circuit varies at a uniform rate of one ampere per second[24]
= 1 H = 1 WbA = 1kgmiddotm2(Amiddots)2
Temperature
Temperature
Name of unit Symbol Definition Conversion to kelvin
degree Celsius degC degC equiv K minus 27315 [K] equiv [degC] + 27315
degree Delisle degDe [K] = 37315 minus [degDe] times 23
degree Fahrenheit degF degF equiv degC times 95 + 32 [K] equiv ([degF] + 45967) times 59
degree Newton degN [K] = [degN] times 10033 + 27315
degree Rankine degR degRa degR equiv K times 95 [K] equiv [degR] times 59
degree Reacuteaumur degReacute [K] = [degReacute] times 54 + 27315
degree Roslashmer degRoslash [K] = ([degRoslash] minus 75) times 4021 + 27315
kelvin (SI baseunit)
K equiv 127316 of the thermodynamic temperature of the triple point of water[8] equiv 1 K
Conversion of units 24
Information entropy
Information entropy
Name of unit Symbol Definition Relation to SI units Relation to bits
SI unit JK equiv JK = 1 JK
nat nip nepit nat equiv kB = 1380 650 5(23) times 10minus23 JK
bit shannon bit b Sh equiv ln(2) times kB = 9569 940 (16) times 10minus24 JK = 1 bit
ban hartley ban Hart equiv ln(10) times kB = 3179 065 3(53) times 10minus23 JK
nibble equiv 4 bits = 3827 976 0(64) times 10minus23 JK = 22 bit
byte B equiv 8 bits = 7655 952 (13) times 10minus23 JK = 23 bit
kilobyte (decimal) kB equiv 1 000 B = 7655 952 (13) times 10minus20 JK
kilobyte (kibibyte) KB KiB equiv 1 024 B = 7839 695 (13) times 10minus20 JK = 210 bit
Often information entropy is measured in shannons whereas the (discrete) storage space of digital devices ismeasured in bits Thus uncompressed redundant data occupy more than one bit of storage per shannon ofinformation entropy The multiples of a bit listed above are usually used with this meaning Other times the bit isused as a measure of information entropy and is thus a synonym of shannon
Luminous intensityThe candela is the preferred nomenclature for the SI unit
Luminous intensity
Name of unit Symbol Definition Relation toSI units
candela (SI baseunit) candle
cd The luminous intensity in a given direction of a source that emits monochromatic radiation offrequency 540 times 1012 hertz and that has a radiant intensity in that direction of 1683 watt persteradian[8]
= 1 cd
candlepower (new) cp equiv cd The use of candlepower as a unit is discouraged due to its ambiguity = 1 cd
candlepower (oldpre-1948)
cp Varies and is poorly reproducible[31] Approximately 0981 cd[14] asymp 0981 cd
Luminance
Conversion of units 25
Luminance
Name of unit Symbol Definition Relation to SI units
candela per square foot cdft2 equiv cdft2 asymp10763910417 cdm2
candela per square inch cdin2 equiv cdin2 asymp 15500031 cdm2
candela per square metre (SI unit) nit (deprecated[14] ) cdm2 equiv cdm2 = 1 cdm2
Name of unit Symbol Definition Relation to SI units
lumen (SIunit)
lm equiv cdmiddotsr = 1 lm = 1 cdmiddotsr
Illuminance
Illuminance
Name of unit Symbol Definition Relation to SI units
footcandle lumen per square foot fc equiv lmft2 = 10763910417 lx
lumen per square inch lmin2 equiv lmin2 asymp 15500031 lx
lux (SI unit) lx equiv lmm2 = 1 lx = 1 lmm2
phot (CGS unit) ph equiv lmcm2 = 1 times 104 lx
Radiation - source activity
Conversion of units 26
Radioactivity
Name of unit Symbol Definition Relation to SI units
becquerel (SIunit)
Bq equiv Number of disintegrations per second = 1 Bq = 1s
curie Ci equiv 37 times 1010 Bq = 37 times 1010 Bq [32]
rutherford (H) rd equiv 1 MBq = 1 times 106 Bq
Please note that although becquerel (Bq) and hertz (Hz) both ultimately refer to the same SI base unit (sminus1) Hz isused only for periodic phenomena and Bq is only used for stochastic processes associated with radioactivity[33]
Radiation - exposure
Radiation - exposure
Name of unit Symbol Definition Relation to SI units
roentgen R 1 R equiv 258 times 10minus4 Ckg[29] = 258 times 10minus4 Ckg
The roentgen is not a SI unit and the NIST strongly discourages its continued use[34]
Radiation - absorbed dose
Radiation - absorbed dose
Name of unit Symbol Definition Relation to SI units
Name of unit Symbol Definition Relation to SI units
Roumlntgen equivalent man rem equiv 001 Sv = 001 Sv
sievert (SI unit) Sv equiv 1 Jkg[33] = 1 Sv
Although the definitions for sievert (Sv) and gray (Gy) would seem to indicate that they measure the same quantitiesthis is not the case The effect of receiving a certain dose of radiation (given as Gy) is variable and depends on manyfactors thus a new unit was needed to denote the biological effectiveness of that dose on the body this is known asthe equivalent dose and is shown in Sv The general relationship between absorbed dose and equivalent dose can berepresented as
H = Q middot D
where H is the equivalent dose D is the absorbed dose and Q is a dimensionless quality factor Thus for anyquantity of D measured in Gy the numerical value for H measured in Sv may be different[36]
Conversion of units 27
Software toolsHome and office computers come with converters in bundled spreadsheet applications or can access free convertersvia the Internet Units and measurements can be easily converted using these tools but only if the units are explicitlydefined and the conversion is compatible (eg cmHg to kPa)
Free conversion softwarebull Units (software) a popular cross-platform command-line utilitybull Converter [37] contextual unit converter for Mozilla Firefox browsersbull Converber [38] portable application converting utilitybull calculla [39] calculla - online web convertersbull iMetrix [40] - unit converter for xpbull uniteasy [41] online scientific unit conversionbull Unit Converter Add-in for Excel [42] - allow a large selection of unit conversions within the Microsoft Excel
spread sheet programbull Unit Converter [43] simple and extensible unit converterbull Portable Unit Converter [44] including 4500 units 33 unit-categories and the possibility to create custom units
General commercial sources of convertersbull Advanced electronic calculators have unit-conversion functionalitybull Spreadsheet programs usually provide conversion functions or formulas or the user can write their ownbull Commercial mathematical scientific and technical applications often include converters
See also
bull Accuracy and precisionbull English unitsbull False precisionbull Imperial unitsbull International System of Unitsbull Mesures usuellesbull Metric system
bull Natural unitsbull Roundingbull Significant figuresbull Temperature conversionbull United States customary unitsbull Units conversion by factor-labelbull Units of measurement
External linksbull British law Units of measurement regulations 1995 [45]
bull ConvertBuster [46] Variety of conversion tools to convert easilybull How Many A dictionary of units of measurement [47]
bull NIST Fundamental physical constants mdash Non-SI units [48]PDF (357 KB)bull NIST Guide to SI Units [49] Many conversion factors listedbull Online Conversion Calculators [50] Very extensive list of conversions from-to equvalent unitsbull The Unified Code for Units of Measure [51]
bull Units Symbols and Conversions XML Dictionary [52]
bull Multilingual Online Conversion of Units [53]
bull Temperature Converter [54]
Conversion of units 28
References[1] United States Naval Observatory (2009) Selected Astronomical Constants 2009 (http asa usno navy mil SecK 2009
Astronomical_Constants_2009 txt) Accessed May 10 2009[2] NIST Reference on Constants Units and Uncertainty (http physics nist gov cgi-bin cuu Valuebohrrada0|search_for=Bohr+
radius)(2006) National Institute of Standards and Technology Retrieved February 22 2008[3] National Institute of Standards and Technology General Tables of Units of Measurement (http ts nist gov WeightsAndMeasures
Publications appxc cfm)[4] Lide D (Ed) (1990) Handbook of Chemistry and Physics (71st ed) Boca Raton FL CRC Press Section 1[5] National Bureau of Standards (June 30 1959) Refinement of values for the yard and the pound Federal Register viewed September 20
2006 at National Geodetic Survey web site (http www ngs noaa gov PUBS_LIB FedRegister FRdoc59-5442 pdf)[6] The International Astronomical Union and Astronomical Units (http www iau org public_press themes measuring )[7] Klein Herbert Arthur (1988) The Science of Measurement a Historical Survey Mineola NY Dover Publications 0-4862-5839-4[8] The International System of Units Section 21 (http www bipm org en si si_brochure chapter2 2-1 ) (8 ed) Bureau International des
Poids et Mesures 2006 retrieved August 26 2009[9] International System of Units (http www bipm org en si si_brochure chapter4 table8 html) 8th ed (2006) Bureau International des
Poids et Mesures Section 41 Table 8[10] P Kenneth Seidelmann Ed (1992) Explanatory Supplement to the Astronomical Almanac Sausalito CA University Science Books p 716
and sv parsec in Glossary[11] Whitelaw Ian (2007) A Measure of All Things The Story of Man and Measurement (http books google com
booksid=3zgGEWM5-iAC) New York Macmillan 0-312-37026-1 p 152[12] De Vinne Theodore Low (1900) The practice of typography a treatise on the processes of type-making the point system the names sizes
styles and prices of plain printing types (http books google com booksid=R4-DjphIpLMC) 2nd ed New York The Century Co p142ndash150
[13] Pasko Wesley Washington (1894) American dictionary of printing and bookmaking (http books google combooksid=Z_QUAAAAIAAJ) (1894) New York Howard Lockwood p 521
[14] Rowlett Russ (2005) How Many A Dictionary of Units of Measurement (http www unc edu ~rowlett units index html)[15] Thompson A and Taylor BN (2008) Guide for the Use of the International System of Units (SI) National Institute of Standards and
Technology Special Publication 811 p 57[16] US Code of Federal Regulations Title 21 Section 1019 Paragraph (b)(5)(viii) (http ecfr gpoaccess gov cgi t text text-idxc=ecframp
rgn=div8amp view=textamp node=212 0 1 1 2 1 1 6amp idno=21) retrieved August 29 2009[17] Barry N Taylor Ed NIST Special Publication 330 The International System of Units (SI) (http physics nist gov Pubs SP330 sp330
pdf) (2001 Edition) Washington US Government Printing Office 43The 12th Conference Generale des Poids et Mesures(CGPM)hellipdeclares that the word ldquolitrerdquo may be employed as a special name for the cubic decimetre
[18] CODATA Value atomic uint of mass (http physics nist gov cgi-bin cuu Valuettme|search_for=atomic+ unit+ of+ mass) (2006)National Institute of Standards and Technology Retrieved 16 September 2008
[19] The Swiss Federal Office for Metrology gives Zentner on a German language web page (http www metas ch de scales systemch html)and quintal on the English translation of that page (http www metas ch en scales systemch html) the unit is marked speacutecifiquementsuisse
[20] Pedersen O (1983) Glossary in Coyne G Hoskin M and Pedersen O Gregorian Reform of the Calendar Proceedings of the VaticanConference to Commemorate its 400th Anniversary Vatican Observatory Available from Astrophysics Data System
[21] Richards EG (1998) Mapping Time Oxford University Press pp 94ndash95 ISBN 0-19-850413-6[22] Steel Duncan (2000) Marking Time John Wiley amp Sons p 46 ISBN 0-471-29827-1[23] CODATA Value atomic unit of force (http physics nist gov cuu Constants ) (2006) National Institute of Standards and Technology
Retrieved September 14 2008[24] [[Comiteacute International des Poids et Mesures (http www bipm org en CIPM db 1946 2 )] Resolution 2] 1946 retrieved August 26
2009[25] Barry N Taylor (April 1995) Guide for the Use of the International System of Units (SI) (http physics nist gov cuu pdf sp811 pdf)
(NIST Special Publication 811) Washington DC US Government Printing Office pp 57ndash68[26] Barry N Taylor (April 1995) Guide for the Use of the International System of Units (SI) (NIST Special Publication 811) Washington DC
US Government Printing Office p 5[27] International System of Units (http www bipm org en si si_brochure chapter4 table7 html) 8th ed (2006) Bureau International des
Poids et Mesures Section 41 Table 7[28] The NIST Reference on Constants Units and Uncertainty (http physics nist gov cgi-bin cuu Valueauedm) 2006 retrieved August
26 2009[29] NIST Guide to SI Units Appendix B9 (http physics nist gov Pubs SP811 appenB9 html) retrieved August 27 2009[30] Standard for the Use of the International System of Units (SI) The Modern Metric System IEEEASTM SI 10-1997 (1997) New York and
West Conshohocken PA Institute of Electrical and Electronics Engineers and American Society for Testing and Materials Tables A1through A5
Conversion of units 29
[31] The NIST Reference on Constants Units and Uncertainty (http physics nist gov cuu Units candela html) retrieved August 28 2009[32] Ambler Thompson amp Barry N Taylor (2008) Guide for the Use of the International System of Units (SI) (http physics nist gov cuu
pdf sp811 pdf) Special Publication 811 Gaithersburg MD National Institute of Standards and Technology p 10[33] The International System of Units Section 222 Table 3 (http www bipm org en si si_brochure chapter2 2-2 table3 html) (8 ed)
Bureau International des Poids et Mesures 2006 retrieved August 27 2009[34] The NIST Guide to the SI (Special Publication 811) section 52 (http physics nist gov Pubs SP811 sec05 html5 2) 2008 retrieved
August 27 2009[35] Ambler Thompson amp Barry N Taylor (2008) Guide for the Use of the International System of Units (SI) (http physics nist gov cuu
pdf sp811 pdf) Special Publication 811 Gaithersburg MD National Institute of Standards and Technology p 5[36] [[Comiteacute international des poids et mesures (http www bipm org en CIPM db 2002 2 )] 2002 Recommendation 2] retrieved
August 27 2009[37] http converter mozdev org[38] http www xyntec com converber htm[39] http www calculla com[40] http illusions hu index phptask=100amp lang=0amp statpage=86[41] http www uniteasy com[42] http www tenderwire com wikipedialandingpage[43] http www kamlex com index phpoption=com_contentamp view=articleamp id=53amp Itemid=55[44] http www sttmedia com unitconverter[45] http www hmso gov uk si si1995 Uksi_19951804_en_2 htm[46] http www convertbuster com[47] http www unc edu ~rowlett units[48] http physics nist gov cuu Document nonsi_in_1998 pdf[49] http physics nist gov Pubs SP811 appenB9 html[50] http www onlineconversion com[51] http aurora rg iupui edu ~schadow units UCUM ucum html[52] http www posc org refs poscUnits20 xml[53] http www imperialtometric com[54] http www tampile com
Article Sources and Contributors 30
Article Sources and ContributorsConversion of units Source httpenwikipediaorgwindexphpoldid=373975089 Contributors 1571781xxx 7 A-giau AVSI Acather96 Ahoerstemeier Alexius08 Altenmann AndreEngels Andrewa Andy120290 Anonymi Ariconte Army1987 ArnoldReinhold Arthur3030 Aspects AxelBoldt AzaToth Azikala BW95 Bdesham Beland Bensaccount Bkumartvm Blackand White BlaiseFEgan BlueEarth Bobblewik Borbrav Bpmullins Bryan Derksen C J B Scholten CORNELIUSSEON CTZMSC3 Calltech Camerajohn Chaosfeary Charles MatthewsChris the speller Cmdrjameson Colonies Chris Conversion script Cope555 Crappy13 Crissov CyrilB DARTH SIDIOUS 2 DMacks DanielCD Dark Formal DarkestSideX DekisugiDenelson83 Dhp1080 Dicklyon DirkvdM Donald Duck Donarreiskoffer Dramatic Dyss DAringsbquougosz Egil Ehrenkater Ejohnsonboulder Elexmax Elf Emokhberi Enon Eob Epbr123Euchiasmus Fathead99 Father Goose Fella22 Femto FernandoAC Fibula Flutefreek Fred Bauder Fredrik Fuhghettaboutit Fuzheado Gaff Gene Nygaard Georgiy1996 Gerry AshtonGiftlite Gilliam Glenn L GoingBatty Goobergunch Gregsexton Greyengine5 Grunt Gurch Gutza HLHJ Haemo Hammersbach Heracles31 Herbee Heron HikerBush Hqb IcairnsIgiffin Indefatigable Isis JBobbitt JHunterJ Jabowery JakeVortex Jamicanmonkey Jason Begin Jay Jc3s5h Jcronen1 Jdoherty Jeffz1 Jeronimo Jimmuhk Jimp Jimwilliams57 JoeinwapJohndburger Josh Parris Jq4bagiq Kaihsu KaneWang Keenan Pepper Kevin Rector KeyStorm Khukri Kurtan Lee Daniel Crocker LightYear Linuxoidoz Liv4christ210 Loggie Lolo252Lupinelawyer M ichaeligl MJCdetroit MTC Mac MacMcF Magore Markus Kuhn Masterqwe MaxHund Maxamegalon2000 Mbeychok Meggar Mh26 Michael Daly Michael Hardy MichelAudy Mikelifeguard Mikhailov Kusserow Mindbuilder Missvain Monger Mr bulow MrOllie MrZhuKeeper Muro de Aguas Mwanner Mwtoews Nandesuka Natkeeran Ndsg NgjaimeNhy67ygv Nick Y Nick123 NickPenguin Ninjagecko Noe Nosilleg Now3r3 Obelix homologator Oldadamml Oleg Alexandrov Olivier Ortolan88 OwenBlacker Pac72 PassargeaPatrick Paul Martin Peter Horn Physchim62 Piels Pierdm Pmanderson Prometheus235 Quadell QuantumEleven Quod erat demonstrandum 314159 Radagast83 Rccoms RedWolfReinyday Revipm Rexparry sydney Reyk Rhetth Rhialto Rich Farmbrough Richard Myers Rjwilmsi Rlsheehan Robin Barry RoySmith Rpwolfgram SD6-Agent SGBailey SamuelLowry Samw Sander123 Seabhcan SebastianHelm Sherbert1 Shinhan Shrew Sietse Snel SimonP Sinbaddasail0r Skotte Smalljim SomeHuman Spencer Srleffler StarwarsmastergeekSteacoon StefanK SteveRamone Stevertigo Stokerm Suisui Sunev Superboy112233 Superm401 Synchronism Tacoman1996 Tarquin Taw Teratornis The Man in Question ThierrycThingg Thinking of England Thunderbird2 Timwi Tobias Hoevekamp Tomasr Tonsofpcs Toon05 Topsykretts2512 Trekphiler Tuwile Twanvl Uday147502 Unitman00 UrhixidurUtherSRG Vargenau Vsmith WarrenPlatts Wasell Welsh Whispering Wikinger Wolfkeeper Wtmitchell XJamRastafire Xenonice Yath Zginder Zibem Zocky Zotel 713 anonymousedits
poise (cgs unit) P equiv 10minus1 Pamiddots = 01 Pamiddots
pound per foot hour lb(ftmiddoth) equiv 1 lb(ftmiddoth) asymp 4133 789 times 10minus4 Pamiddots
pound per foot second lb(ftmiddots) equiv 1 lb(ftmiddots) asymp 1488164 Pamiddots
pound-force second per square foot lbfmiddotsft2 equiv 1 lbfmiddotsft2 asymp 4788026 Pamiddots
pound-force second per square inch lbfmiddotsin2 equiv 1 lbfmiddotsin2 asymp 6894757 Pamiddots
Conversion of units 21
Kinematic viscosity
Kinematic viscosity
Name of unit Symbol Definition Relation to SI units
square foot per second ft2s equiv 1 ft2s = 009290304 m2s
square metre per second (SI unit) m2s equiv 1 m2s = 1 m2s
stokes (cgs unit) St equiv10minus4 m2s
= 10minus4 m2s
Electric current
Electric current
Name of unit Symbol Definition Relation to SI units
ampere (SI base unit) A equiv The constant current needed to produce a force of 2 times 10minus7 newton per metre betweentwo straight parallel conductors of infinite length and negligible circular cross-sectionplaced one metre apart in a vacuum[8]
= 1 A
electromagnetic unitabampere (cgs unit)
abamp equiv 10 A = 10 A
esu per secondstatampere (cgs unit)
esus equiv (01 Amiddotms) c asymp3335641 times 10minus10 A
Electric charge
Electric charge
Name of unit Symbol Definition Relation to SI units
abcoulomb electromagnetic unit (cgsunit)
abC emu equiv 10 C = 10 C
atomic unit of charge au equiv e asymp 1602 176462 times 10minus19 C
coulomb (SI unit) C equiv The amount of electricity carried in one second of time by oneampere of current[24]
= 1 C = 1 Amiddots
faraday F equiv 1 mol times NAmiddote asymp 96 4853383 C
statcoulomb franklin electrostatic unit(cgs unit)
statC Fresu
equiv (01 Amiddotm) c asymp 3335 641 times 10minus10 C
Conversion of units 22
Electric dipole
Electric dipole
Name of unit Symbol Definition Relation to SI units
atomic unit of electric dipole moment ea0 asymp 8478 352 81 times 10minus30
Cmiddotm[28]
Electromotive force electric potential difference
Voltage electromotive force
Name ofunit
Symbol Definition Relation to SI units
abvolt (cgsunit)
abV equiv 1 times 10minus8 V = 1 times 10minus8 V
statvolt (cgsunit)
statV equiv cmiddot (1 μJAmiddotm) = 299792 458 V
volt (SIunit)
V The difference in electric potential across two points along a conducting wire carrying one ampereof constant current when the power dissipated between the points equals one watt[24]
= 1 V = 1 WA = 1kgmiddotm2(Amiddots3)
Electrical resistance
Electrical resistance
Name ofunit
Symbol Definition Relation to SI units
ohm (SIunit)
Ω The resistance between two points in a conductor when one volt of electric potential differenceapplied to these points produces one ampere of current in the conductor[24]
= 1 Ω = 1 VA = 1kgmiddotm2(A2middots3)
Capacitance
Capacitors ability to store charge
Name ofunit
Symbol Definition Relation to SI units
farad (SIunit)
F The capacitance between two parallel plates that results in one volt of potential difference whencharged by one coulomb of electricity[24]
= 1 F = 1 CV = 1A2middots4(kgmiddotm2)
Conversion of units 23
Magnetic flux
magnetic flux
Name of unit Symbol Definition Relation to SI units
maxwell (CGSunit)
Mx equiv 10minus8 Wb[29] = 1 times 10minus8 Wb
weber (SIunit)
Wb Magnetic flux which linking a circuit of one turn would produce in it an electromotive force of1 volt if it were reduced to zero at a uniform rate in 1 second[24]
= 1 Wb = 1 Vmiddots = 1kgmiddotm2(Amiddots2)
Magnetic flux density
What physicists call Magnetic field is called Magnetic flux density by electrical engineersand magnetic induction by applied mathematicians and electrical engineers
Name of unit Symbol Definition Relation to SI units
gauss (CGS unit) G equiv Mxcm2 = 10minus4
T= 1 times 10minus4 T [30]
tesla (SI unit) T equiv Wbm2 = 1 T = 1 Wbm2 = 1kg(Amiddots2)
Inductance
Inductance
Name ofunit
Symbol Definition Relation to SI units
henry (SIunit)
H The inductance of a closed circuit that produces one volt of electromotive force when the current inthe circuit varies at a uniform rate of one ampere per second[24]
= 1 H = 1 WbA = 1kgmiddotm2(Amiddots)2
Temperature
Temperature
Name of unit Symbol Definition Conversion to kelvin
degree Celsius degC degC equiv K minus 27315 [K] equiv [degC] + 27315
degree Delisle degDe [K] = 37315 minus [degDe] times 23
degree Fahrenheit degF degF equiv degC times 95 + 32 [K] equiv ([degF] + 45967) times 59
degree Newton degN [K] = [degN] times 10033 + 27315
degree Rankine degR degRa degR equiv K times 95 [K] equiv [degR] times 59
degree Reacuteaumur degReacute [K] = [degReacute] times 54 + 27315
degree Roslashmer degRoslash [K] = ([degRoslash] minus 75) times 4021 + 27315
kelvin (SI baseunit)
K equiv 127316 of the thermodynamic temperature of the triple point of water[8] equiv 1 K
Conversion of units 24
Information entropy
Information entropy
Name of unit Symbol Definition Relation to SI units Relation to bits
SI unit JK equiv JK = 1 JK
nat nip nepit nat equiv kB = 1380 650 5(23) times 10minus23 JK
bit shannon bit b Sh equiv ln(2) times kB = 9569 940 (16) times 10minus24 JK = 1 bit
ban hartley ban Hart equiv ln(10) times kB = 3179 065 3(53) times 10minus23 JK
nibble equiv 4 bits = 3827 976 0(64) times 10minus23 JK = 22 bit
byte B equiv 8 bits = 7655 952 (13) times 10minus23 JK = 23 bit
kilobyte (decimal) kB equiv 1 000 B = 7655 952 (13) times 10minus20 JK
kilobyte (kibibyte) KB KiB equiv 1 024 B = 7839 695 (13) times 10minus20 JK = 210 bit
Often information entropy is measured in shannons whereas the (discrete) storage space of digital devices ismeasured in bits Thus uncompressed redundant data occupy more than one bit of storage per shannon ofinformation entropy The multiples of a bit listed above are usually used with this meaning Other times the bit isused as a measure of information entropy and is thus a synonym of shannon
Luminous intensityThe candela is the preferred nomenclature for the SI unit
Luminous intensity
Name of unit Symbol Definition Relation toSI units
candela (SI baseunit) candle
cd The luminous intensity in a given direction of a source that emits monochromatic radiation offrequency 540 times 1012 hertz and that has a radiant intensity in that direction of 1683 watt persteradian[8]
= 1 cd
candlepower (new) cp equiv cd The use of candlepower as a unit is discouraged due to its ambiguity = 1 cd
candlepower (oldpre-1948)
cp Varies and is poorly reproducible[31] Approximately 0981 cd[14] asymp 0981 cd
Luminance
Conversion of units 25
Luminance
Name of unit Symbol Definition Relation to SI units
candela per square foot cdft2 equiv cdft2 asymp10763910417 cdm2
candela per square inch cdin2 equiv cdin2 asymp 15500031 cdm2
candela per square metre (SI unit) nit (deprecated[14] ) cdm2 equiv cdm2 = 1 cdm2
Name of unit Symbol Definition Relation to SI units
lumen (SIunit)
lm equiv cdmiddotsr = 1 lm = 1 cdmiddotsr
Illuminance
Illuminance
Name of unit Symbol Definition Relation to SI units
footcandle lumen per square foot fc equiv lmft2 = 10763910417 lx
lumen per square inch lmin2 equiv lmin2 asymp 15500031 lx
lux (SI unit) lx equiv lmm2 = 1 lx = 1 lmm2
phot (CGS unit) ph equiv lmcm2 = 1 times 104 lx
Radiation - source activity
Conversion of units 26
Radioactivity
Name of unit Symbol Definition Relation to SI units
becquerel (SIunit)
Bq equiv Number of disintegrations per second = 1 Bq = 1s
curie Ci equiv 37 times 1010 Bq = 37 times 1010 Bq [32]
rutherford (H) rd equiv 1 MBq = 1 times 106 Bq
Please note that although becquerel (Bq) and hertz (Hz) both ultimately refer to the same SI base unit (sminus1) Hz isused only for periodic phenomena and Bq is only used for stochastic processes associated with radioactivity[33]
Radiation - exposure
Radiation - exposure
Name of unit Symbol Definition Relation to SI units
roentgen R 1 R equiv 258 times 10minus4 Ckg[29] = 258 times 10minus4 Ckg
The roentgen is not a SI unit and the NIST strongly discourages its continued use[34]
Radiation - absorbed dose
Radiation - absorbed dose
Name of unit Symbol Definition Relation to SI units
Name of unit Symbol Definition Relation to SI units
Roumlntgen equivalent man rem equiv 001 Sv = 001 Sv
sievert (SI unit) Sv equiv 1 Jkg[33] = 1 Sv
Although the definitions for sievert (Sv) and gray (Gy) would seem to indicate that they measure the same quantitiesthis is not the case The effect of receiving a certain dose of radiation (given as Gy) is variable and depends on manyfactors thus a new unit was needed to denote the biological effectiveness of that dose on the body this is known asthe equivalent dose and is shown in Sv The general relationship between absorbed dose and equivalent dose can berepresented as
H = Q middot D
where H is the equivalent dose D is the absorbed dose and Q is a dimensionless quality factor Thus for anyquantity of D measured in Gy the numerical value for H measured in Sv may be different[36]
Conversion of units 27
Software toolsHome and office computers come with converters in bundled spreadsheet applications or can access free convertersvia the Internet Units and measurements can be easily converted using these tools but only if the units are explicitlydefined and the conversion is compatible (eg cmHg to kPa)
Free conversion softwarebull Units (software) a popular cross-platform command-line utilitybull Converter [37] contextual unit converter for Mozilla Firefox browsersbull Converber [38] portable application converting utilitybull calculla [39] calculla - online web convertersbull iMetrix [40] - unit converter for xpbull uniteasy [41] online scientific unit conversionbull Unit Converter Add-in for Excel [42] - allow a large selection of unit conversions within the Microsoft Excel
spread sheet programbull Unit Converter [43] simple and extensible unit converterbull Portable Unit Converter [44] including 4500 units 33 unit-categories and the possibility to create custom units
General commercial sources of convertersbull Advanced electronic calculators have unit-conversion functionalitybull Spreadsheet programs usually provide conversion functions or formulas or the user can write their ownbull Commercial mathematical scientific and technical applications often include converters
See also
bull Accuracy and precisionbull English unitsbull False precisionbull Imperial unitsbull International System of Unitsbull Mesures usuellesbull Metric system
bull Natural unitsbull Roundingbull Significant figuresbull Temperature conversionbull United States customary unitsbull Units conversion by factor-labelbull Units of measurement
External linksbull British law Units of measurement regulations 1995 [45]
bull ConvertBuster [46] Variety of conversion tools to convert easilybull How Many A dictionary of units of measurement [47]
bull NIST Fundamental physical constants mdash Non-SI units [48]PDF (357 KB)bull NIST Guide to SI Units [49] Many conversion factors listedbull Online Conversion Calculators [50] Very extensive list of conversions from-to equvalent unitsbull The Unified Code for Units of Measure [51]
bull Units Symbols and Conversions XML Dictionary [52]
bull Multilingual Online Conversion of Units [53]
bull Temperature Converter [54]
Conversion of units 28
References[1] United States Naval Observatory (2009) Selected Astronomical Constants 2009 (http asa usno navy mil SecK 2009
Astronomical_Constants_2009 txt) Accessed May 10 2009[2] NIST Reference on Constants Units and Uncertainty (http physics nist gov cgi-bin cuu Valuebohrrada0|search_for=Bohr+
radius)(2006) National Institute of Standards and Technology Retrieved February 22 2008[3] National Institute of Standards and Technology General Tables of Units of Measurement (http ts nist gov WeightsAndMeasures
Publications appxc cfm)[4] Lide D (Ed) (1990) Handbook of Chemistry and Physics (71st ed) Boca Raton FL CRC Press Section 1[5] National Bureau of Standards (June 30 1959) Refinement of values for the yard and the pound Federal Register viewed September 20
2006 at National Geodetic Survey web site (http www ngs noaa gov PUBS_LIB FedRegister FRdoc59-5442 pdf)[6] The International Astronomical Union and Astronomical Units (http www iau org public_press themes measuring )[7] Klein Herbert Arthur (1988) The Science of Measurement a Historical Survey Mineola NY Dover Publications 0-4862-5839-4[8] The International System of Units Section 21 (http www bipm org en si si_brochure chapter2 2-1 ) (8 ed) Bureau International des
Poids et Mesures 2006 retrieved August 26 2009[9] International System of Units (http www bipm org en si si_brochure chapter4 table8 html) 8th ed (2006) Bureau International des
Poids et Mesures Section 41 Table 8[10] P Kenneth Seidelmann Ed (1992) Explanatory Supplement to the Astronomical Almanac Sausalito CA University Science Books p 716
and sv parsec in Glossary[11] Whitelaw Ian (2007) A Measure of All Things The Story of Man and Measurement (http books google com
booksid=3zgGEWM5-iAC) New York Macmillan 0-312-37026-1 p 152[12] De Vinne Theodore Low (1900) The practice of typography a treatise on the processes of type-making the point system the names sizes
styles and prices of plain printing types (http books google com booksid=R4-DjphIpLMC) 2nd ed New York The Century Co p142ndash150
[13] Pasko Wesley Washington (1894) American dictionary of printing and bookmaking (http books google combooksid=Z_QUAAAAIAAJ) (1894) New York Howard Lockwood p 521
[14] Rowlett Russ (2005) How Many A Dictionary of Units of Measurement (http www unc edu ~rowlett units index html)[15] Thompson A and Taylor BN (2008) Guide for the Use of the International System of Units (SI) National Institute of Standards and
Technology Special Publication 811 p 57[16] US Code of Federal Regulations Title 21 Section 1019 Paragraph (b)(5)(viii) (http ecfr gpoaccess gov cgi t text text-idxc=ecframp
rgn=div8amp view=textamp node=212 0 1 1 2 1 1 6amp idno=21) retrieved August 29 2009[17] Barry N Taylor Ed NIST Special Publication 330 The International System of Units (SI) (http physics nist gov Pubs SP330 sp330
pdf) (2001 Edition) Washington US Government Printing Office 43The 12th Conference Generale des Poids et Mesures(CGPM)hellipdeclares that the word ldquolitrerdquo may be employed as a special name for the cubic decimetre
[18] CODATA Value atomic uint of mass (http physics nist gov cgi-bin cuu Valuettme|search_for=atomic+ unit+ of+ mass) (2006)National Institute of Standards and Technology Retrieved 16 September 2008
[19] The Swiss Federal Office for Metrology gives Zentner on a German language web page (http www metas ch de scales systemch html)and quintal on the English translation of that page (http www metas ch en scales systemch html) the unit is marked speacutecifiquementsuisse
[20] Pedersen O (1983) Glossary in Coyne G Hoskin M and Pedersen O Gregorian Reform of the Calendar Proceedings of the VaticanConference to Commemorate its 400th Anniversary Vatican Observatory Available from Astrophysics Data System
[21] Richards EG (1998) Mapping Time Oxford University Press pp 94ndash95 ISBN 0-19-850413-6[22] Steel Duncan (2000) Marking Time John Wiley amp Sons p 46 ISBN 0-471-29827-1[23] CODATA Value atomic unit of force (http physics nist gov cuu Constants ) (2006) National Institute of Standards and Technology
Retrieved September 14 2008[24] [[Comiteacute International des Poids et Mesures (http www bipm org en CIPM db 1946 2 )] Resolution 2] 1946 retrieved August 26
2009[25] Barry N Taylor (April 1995) Guide for the Use of the International System of Units (SI) (http physics nist gov cuu pdf sp811 pdf)
(NIST Special Publication 811) Washington DC US Government Printing Office pp 57ndash68[26] Barry N Taylor (April 1995) Guide for the Use of the International System of Units (SI) (NIST Special Publication 811) Washington DC
US Government Printing Office p 5[27] International System of Units (http www bipm org en si si_brochure chapter4 table7 html) 8th ed (2006) Bureau International des
Poids et Mesures Section 41 Table 7[28] The NIST Reference on Constants Units and Uncertainty (http physics nist gov cgi-bin cuu Valueauedm) 2006 retrieved August
26 2009[29] NIST Guide to SI Units Appendix B9 (http physics nist gov Pubs SP811 appenB9 html) retrieved August 27 2009[30] Standard for the Use of the International System of Units (SI) The Modern Metric System IEEEASTM SI 10-1997 (1997) New York and
West Conshohocken PA Institute of Electrical and Electronics Engineers and American Society for Testing and Materials Tables A1through A5
Conversion of units 29
[31] The NIST Reference on Constants Units and Uncertainty (http physics nist gov cuu Units candela html) retrieved August 28 2009[32] Ambler Thompson amp Barry N Taylor (2008) Guide for the Use of the International System of Units (SI) (http physics nist gov cuu
pdf sp811 pdf) Special Publication 811 Gaithersburg MD National Institute of Standards and Technology p 10[33] The International System of Units Section 222 Table 3 (http www bipm org en si si_brochure chapter2 2-2 table3 html) (8 ed)
Bureau International des Poids et Mesures 2006 retrieved August 27 2009[34] The NIST Guide to the SI (Special Publication 811) section 52 (http physics nist gov Pubs SP811 sec05 html5 2) 2008 retrieved
August 27 2009[35] Ambler Thompson amp Barry N Taylor (2008) Guide for the Use of the International System of Units (SI) (http physics nist gov cuu
pdf sp811 pdf) Special Publication 811 Gaithersburg MD National Institute of Standards and Technology p 5[36] [[Comiteacute international des poids et mesures (http www bipm org en CIPM db 2002 2 )] 2002 Recommendation 2] retrieved
August 27 2009[37] http converter mozdev org[38] http www xyntec com converber htm[39] http www calculla com[40] http illusions hu index phptask=100amp lang=0amp statpage=86[41] http www uniteasy com[42] http www tenderwire com wikipedialandingpage[43] http www kamlex com index phpoption=com_contentamp view=articleamp id=53amp Itemid=55[44] http www sttmedia com unitconverter[45] http www hmso gov uk si si1995 Uksi_19951804_en_2 htm[46] http www convertbuster com[47] http www unc edu ~rowlett units[48] http physics nist gov cuu Document nonsi_in_1998 pdf[49] http physics nist gov Pubs SP811 appenB9 html[50] http www onlineconversion com[51] http aurora rg iupui edu ~schadow units UCUM ucum html[52] http www posc org refs poscUnits20 xml[53] http www imperialtometric com[54] http www tampile com
Article Sources and Contributors 30
Article Sources and ContributorsConversion of units Source httpenwikipediaorgwindexphpoldid=373975089 Contributors 1571781xxx 7 A-giau AVSI Acather96 Ahoerstemeier Alexius08 Altenmann AndreEngels Andrewa Andy120290 Anonymi Ariconte Army1987 ArnoldReinhold Arthur3030 Aspects AxelBoldt AzaToth Azikala BW95 Bdesham Beland Bensaccount Bkumartvm Blackand White BlaiseFEgan BlueEarth Bobblewik Borbrav Bpmullins Bryan Derksen C J B Scholten CORNELIUSSEON CTZMSC3 Calltech Camerajohn Chaosfeary Charles MatthewsChris the speller Cmdrjameson Colonies Chris Conversion script Cope555 Crappy13 Crissov CyrilB DARTH SIDIOUS 2 DMacks DanielCD Dark Formal DarkestSideX DekisugiDenelson83 Dhp1080 Dicklyon DirkvdM Donald Duck Donarreiskoffer Dramatic Dyss DAringsbquougosz Egil Ehrenkater Ejohnsonboulder Elexmax Elf Emokhberi Enon Eob Epbr123Euchiasmus Fathead99 Father Goose Fella22 Femto FernandoAC Fibula Flutefreek Fred Bauder Fredrik Fuhghettaboutit Fuzheado Gaff Gene Nygaard Georgiy1996 Gerry AshtonGiftlite Gilliam Glenn L GoingBatty Goobergunch Gregsexton Greyengine5 Grunt Gurch Gutza HLHJ Haemo Hammersbach Heracles31 Herbee Heron HikerBush Hqb IcairnsIgiffin Indefatigable Isis JBobbitt JHunterJ Jabowery JakeVortex Jamicanmonkey Jason Begin Jay Jc3s5h Jcronen1 Jdoherty Jeffz1 Jeronimo Jimmuhk Jimp Jimwilliams57 JoeinwapJohndburger Josh Parris Jq4bagiq Kaihsu KaneWang Keenan Pepper Kevin Rector KeyStorm Khukri Kurtan Lee Daniel Crocker LightYear Linuxoidoz Liv4christ210 Loggie Lolo252Lupinelawyer M ichaeligl MJCdetroit MTC Mac MacMcF Magore Markus Kuhn Masterqwe MaxHund Maxamegalon2000 Mbeychok Meggar Mh26 Michael Daly Michael Hardy MichelAudy Mikelifeguard Mikhailov Kusserow Mindbuilder Missvain Monger Mr bulow MrOllie MrZhuKeeper Muro de Aguas Mwanner Mwtoews Nandesuka Natkeeran Ndsg NgjaimeNhy67ygv Nick Y Nick123 NickPenguin Ninjagecko Noe Nosilleg Now3r3 Obelix homologator Oldadamml Oleg Alexandrov Olivier Ortolan88 OwenBlacker Pac72 PassargeaPatrick Paul Martin Peter Horn Physchim62 Piels Pierdm Pmanderson Prometheus235 Quadell QuantumEleven Quod erat demonstrandum 314159 Radagast83 Rccoms RedWolfReinyday Revipm Rexparry sydney Reyk Rhetth Rhialto Rich Farmbrough Richard Myers Rjwilmsi Rlsheehan Robin Barry RoySmith Rpwolfgram SD6-Agent SGBailey SamuelLowry Samw Sander123 Seabhcan SebastianHelm Sherbert1 Shinhan Shrew Sietse Snel SimonP Sinbaddasail0r Skotte Smalljim SomeHuman Spencer Srleffler StarwarsmastergeekSteacoon StefanK SteveRamone Stevertigo Stokerm Suisui Sunev Superboy112233 Superm401 Synchronism Tacoman1996 Tarquin Taw Teratornis The Man in Question ThierrycThingg Thinking of England Thunderbird2 Timwi Tobias Hoevekamp Tomasr Tonsofpcs Toon05 Topsykretts2512 Trekphiler Tuwile Twanvl Uday147502 Unitman00 UrhixidurUtherSRG Vargenau Vsmith WarrenPlatts Wasell Welsh Whispering Wikinger Wolfkeeper Wtmitchell XJamRastafire Xenonice Yath Zginder Zibem Zocky Zotel 713 anonymousedits
poise (cgs unit) P equiv 10minus1 Pamiddots = 01 Pamiddots
pound per foot hour lb(ftmiddoth) equiv 1 lb(ftmiddoth) asymp 4133 789 times 10minus4 Pamiddots
pound per foot second lb(ftmiddots) equiv 1 lb(ftmiddots) asymp 1488164 Pamiddots
pound-force second per square foot lbfmiddotsft2 equiv 1 lbfmiddotsft2 asymp 4788026 Pamiddots
pound-force second per square inch lbfmiddotsin2 equiv 1 lbfmiddotsin2 asymp 6894757 Pamiddots
Conversion of units 21
Kinematic viscosity
Kinematic viscosity
Name of unit Symbol Definition Relation to SI units
square foot per second ft2s equiv 1 ft2s = 009290304 m2s
square metre per second (SI unit) m2s equiv 1 m2s = 1 m2s
stokes (cgs unit) St equiv10minus4 m2s
= 10minus4 m2s
Electric current
Electric current
Name of unit Symbol Definition Relation to SI units
ampere (SI base unit) A equiv The constant current needed to produce a force of 2 times 10minus7 newton per metre betweentwo straight parallel conductors of infinite length and negligible circular cross-sectionplaced one metre apart in a vacuum[8]
= 1 A
electromagnetic unitabampere (cgs unit)
abamp equiv 10 A = 10 A
esu per secondstatampere (cgs unit)
esus equiv (01 Amiddotms) c asymp3335641 times 10minus10 A
Electric charge
Electric charge
Name of unit Symbol Definition Relation to SI units
abcoulomb electromagnetic unit (cgsunit)
abC emu equiv 10 C = 10 C
atomic unit of charge au equiv e asymp 1602 176462 times 10minus19 C
coulomb (SI unit) C equiv The amount of electricity carried in one second of time by oneampere of current[24]
= 1 C = 1 Amiddots
faraday F equiv 1 mol times NAmiddote asymp 96 4853383 C
statcoulomb franklin electrostatic unit(cgs unit)
statC Fresu
equiv (01 Amiddotm) c asymp 3335 641 times 10minus10 C
Conversion of units 22
Electric dipole
Electric dipole
Name of unit Symbol Definition Relation to SI units
atomic unit of electric dipole moment ea0 asymp 8478 352 81 times 10minus30
Cmiddotm[28]
Electromotive force electric potential difference
Voltage electromotive force
Name ofunit
Symbol Definition Relation to SI units
abvolt (cgsunit)
abV equiv 1 times 10minus8 V = 1 times 10minus8 V
statvolt (cgsunit)
statV equiv cmiddot (1 μJAmiddotm) = 299792 458 V
volt (SIunit)
V The difference in electric potential across two points along a conducting wire carrying one ampereof constant current when the power dissipated between the points equals one watt[24]
= 1 V = 1 WA = 1kgmiddotm2(Amiddots3)
Electrical resistance
Electrical resistance
Name ofunit
Symbol Definition Relation to SI units
ohm (SIunit)
Ω The resistance between two points in a conductor when one volt of electric potential differenceapplied to these points produces one ampere of current in the conductor[24]
= 1 Ω = 1 VA = 1kgmiddotm2(A2middots3)
Capacitance
Capacitors ability to store charge
Name ofunit
Symbol Definition Relation to SI units
farad (SIunit)
F The capacitance between two parallel plates that results in one volt of potential difference whencharged by one coulomb of electricity[24]
= 1 F = 1 CV = 1A2middots4(kgmiddotm2)
Conversion of units 23
Magnetic flux
magnetic flux
Name of unit Symbol Definition Relation to SI units
maxwell (CGSunit)
Mx equiv 10minus8 Wb[29] = 1 times 10minus8 Wb
weber (SIunit)
Wb Magnetic flux which linking a circuit of one turn would produce in it an electromotive force of1 volt if it were reduced to zero at a uniform rate in 1 second[24]
= 1 Wb = 1 Vmiddots = 1kgmiddotm2(Amiddots2)
Magnetic flux density
What physicists call Magnetic field is called Magnetic flux density by electrical engineersand magnetic induction by applied mathematicians and electrical engineers
Name of unit Symbol Definition Relation to SI units
gauss (CGS unit) G equiv Mxcm2 = 10minus4
T= 1 times 10minus4 T [30]
tesla (SI unit) T equiv Wbm2 = 1 T = 1 Wbm2 = 1kg(Amiddots2)
Inductance
Inductance
Name ofunit
Symbol Definition Relation to SI units
henry (SIunit)
H The inductance of a closed circuit that produces one volt of electromotive force when the current inthe circuit varies at a uniform rate of one ampere per second[24]
= 1 H = 1 WbA = 1kgmiddotm2(Amiddots)2
Temperature
Temperature
Name of unit Symbol Definition Conversion to kelvin
degree Celsius degC degC equiv K minus 27315 [K] equiv [degC] + 27315
degree Delisle degDe [K] = 37315 minus [degDe] times 23
degree Fahrenheit degF degF equiv degC times 95 + 32 [K] equiv ([degF] + 45967) times 59
degree Newton degN [K] = [degN] times 10033 + 27315
degree Rankine degR degRa degR equiv K times 95 [K] equiv [degR] times 59
degree Reacuteaumur degReacute [K] = [degReacute] times 54 + 27315
degree Roslashmer degRoslash [K] = ([degRoslash] minus 75) times 4021 + 27315
kelvin (SI baseunit)
K equiv 127316 of the thermodynamic temperature of the triple point of water[8] equiv 1 K
Conversion of units 24
Information entropy
Information entropy
Name of unit Symbol Definition Relation to SI units Relation to bits
SI unit JK equiv JK = 1 JK
nat nip nepit nat equiv kB = 1380 650 5(23) times 10minus23 JK
bit shannon bit b Sh equiv ln(2) times kB = 9569 940 (16) times 10minus24 JK = 1 bit
ban hartley ban Hart equiv ln(10) times kB = 3179 065 3(53) times 10minus23 JK
nibble equiv 4 bits = 3827 976 0(64) times 10minus23 JK = 22 bit
byte B equiv 8 bits = 7655 952 (13) times 10minus23 JK = 23 bit
kilobyte (decimal) kB equiv 1 000 B = 7655 952 (13) times 10minus20 JK
kilobyte (kibibyte) KB KiB equiv 1 024 B = 7839 695 (13) times 10minus20 JK = 210 bit
Often information entropy is measured in shannons whereas the (discrete) storage space of digital devices ismeasured in bits Thus uncompressed redundant data occupy more than one bit of storage per shannon ofinformation entropy The multiples of a bit listed above are usually used with this meaning Other times the bit isused as a measure of information entropy and is thus a synonym of shannon
Luminous intensityThe candela is the preferred nomenclature for the SI unit
Luminous intensity
Name of unit Symbol Definition Relation toSI units
candela (SI baseunit) candle
cd The luminous intensity in a given direction of a source that emits monochromatic radiation offrequency 540 times 1012 hertz and that has a radiant intensity in that direction of 1683 watt persteradian[8]
= 1 cd
candlepower (new) cp equiv cd The use of candlepower as a unit is discouraged due to its ambiguity = 1 cd
candlepower (oldpre-1948)
cp Varies and is poorly reproducible[31] Approximately 0981 cd[14] asymp 0981 cd
Luminance
Conversion of units 25
Luminance
Name of unit Symbol Definition Relation to SI units
candela per square foot cdft2 equiv cdft2 asymp10763910417 cdm2
candela per square inch cdin2 equiv cdin2 asymp 15500031 cdm2
candela per square metre (SI unit) nit (deprecated[14] ) cdm2 equiv cdm2 = 1 cdm2
Name of unit Symbol Definition Relation to SI units
lumen (SIunit)
lm equiv cdmiddotsr = 1 lm = 1 cdmiddotsr
Illuminance
Illuminance
Name of unit Symbol Definition Relation to SI units
footcandle lumen per square foot fc equiv lmft2 = 10763910417 lx
lumen per square inch lmin2 equiv lmin2 asymp 15500031 lx
lux (SI unit) lx equiv lmm2 = 1 lx = 1 lmm2
phot (CGS unit) ph equiv lmcm2 = 1 times 104 lx
Radiation - source activity
Conversion of units 26
Radioactivity
Name of unit Symbol Definition Relation to SI units
becquerel (SIunit)
Bq equiv Number of disintegrations per second = 1 Bq = 1s
curie Ci equiv 37 times 1010 Bq = 37 times 1010 Bq [32]
rutherford (H) rd equiv 1 MBq = 1 times 106 Bq
Please note that although becquerel (Bq) and hertz (Hz) both ultimately refer to the same SI base unit (sminus1) Hz isused only for periodic phenomena and Bq is only used for stochastic processes associated with radioactivity[33]
Radiation - exposure
Radiation - exposure
Name of unit Symbol Definition Relation to SI units
roentgen R 1 R equiv 258 times 10minus4 Ckg[29] = 258 times 10minus4 Ckg
The roentgen is not a SI unit and the NIST strongly discourages its continued use[34]
Radiation - absorbed dose
Radiation - absorbed dose
Name of unit Symbol Definition Relation to SI units
Name of unit Symbol Definition Relation to SI units
Roumlntgen equivalent man rem equiv 001 Sv = 001 Sv
sievert (SI unit) Sv equiv 1 Jkg[33] = 1 Sv
Although the definitions for sievert (Sv) and gray (Gy) would seem to indicate that they measure the same quantitiesthis is not the case The effect of receiving a certain dose of radiation (given as Gy) is variable and depends on manyfactors thus a new unit was needed to denote the biological effectiveness of that dose on the body this is known asthe equivalent dose and is shown in Sv The general relationship between absorbed dose and equivalent dose can berepresented as
H = Q middot D
where H is the equivalent dose D is the absorbed dose and Q is a dimensionless quality factor Thus for anyquantity of D measured in Gy the numerical value for H measured in Sv may be different[36]
Conversion of units 27
Software toolsHome and office computers come with converters in bundled spreadsheet applications or can access free convertersvia the Internet Units and measurements can be easily converted using these tools but only if the units are explicitlydefined and the conversion is compatible (eg cmHg to kPa)
Free conversion softwarebull Units (software) a popular cross-platform command-line utilitybull Converter [37] contextual unit converter for Mozilla Firefox browsersbull Converber [38] portable application converting utilitybull calculla [39] calculla - online web convertersbull iMetrix [40] - unit converter for xpbull uniteasy [41] online scientific unit conversionbull Unit Converter Add-in for Excel [42] - allow a large selection of unit conversions within the Microsoft Excel
spread sheet programbull Unit Converter [43] simple and extensible unit converterbull Portable Unit Converter [44] including 4500 units 33 unit-categories and the possibility to create custom units
General commercial sources of convertersbull Advanced electronic calculators have unit-conversion functionalitybull Spreadsheet programs usually provide conversion functions or formulas or the user can write their ownbull Commercial mathematical scientific and technical applications often include converters
See also
bull Accuracy and precisionbull English unitsbull False precisionbull Imperial unitsbull International System of Unitsbull Mesures usuellesbull Metric system
bull Natural unitsbull Roundingbull Significant figuresbull Temperature conversionbull United States customary unitsbull Units conversion by factor-labelbull Units of measurement
External linksbull British law Units of measurement regulations 1995 [45]
bull ConvertBuster [46] Variety of conversion tools to convert easilybull How Many A dictionary of units of measurement [47]
bull NIST Fundamental physical constants mdash Non-SI units [48]PDF (357 KB)bull NIST Guide to SI Units [49] Many conversion factors listedbull Online Conversion Calculators [50] Very extensive list of conversions from-to equvalent unitsbull The Unified Code for Units of Measure [51]
bull Units Symbols and Conversions XML Dictionary [52]
bull Multilingual Online Conversion of Units [53]
bull Temperature Converter [54]
Conversion of units 28
References[1] United States Naval Observatory (2009) Selected Astronomical Constants 2009 (http asa usno navy mil SecK 2009
Astronomical_Constants_2009 txt) Accessed May 10 2009[2] NIST Reference on Constants Units and Uncertainty (http physics nist gov cgi-bin cuu Valuebohrrada0|search_for=Bohr+
radius)(2006) National Institute of Standards and Technology Retrieved February 22 2008[3] National Institute of Standards and Technology General Tables of Units of Measurement (http ts nist gov WeightsAndMeasures
Publications appxc cfm)[4] Lide D (Ed) (1990) Handbook of Chemistry and Physics (71st ed) Boca Raton FL CRC Press Section 1[5] National Bureau of Standards (June 30 1959) Refinement of values for the yard and the pound Federal Register viewed September 20
2006 at National Geodetic Survey web site (http www ngs noaa gov PUBS_LIB FedRegister FRdoc59-5442 pdf)[6] The International Astronomical Union and Astronomical Units (http www iau org public_press themes measuring )[7] Klein Herbert Arthur (1988) The Science of Measurement a Historical Survey Mineola NY Dover Publications 0-4862-5839-4[8] The International System of Units Section 21 (http www bipm org en si si_brochure chapter2 2-1 ) (8 ed) Bureau International des
Poids et Mesures 2006 retrieved August 26 2009[9] International System of Units (http www bipm org en si si_brochure chapter4 table8 html) 8th ed (2006) Bureau International des
Poids et Mesures Section 41 Table 8[10] P Kenneth Seidelmann Ed (1992) Explanatory Supplement to the Astronomical Almanac Sausalito CA University Science Books p 716
and sv parsec in Glossary[11] Whitelaw Ian (2007) A Measure of All Things The Story of Man and Measurement (http books google com
booksid=3zgGEWM5-iAC) New York Macmillan 0-312-37026-1 p 152[12] De Vinne Theodore Low (1900) The practice of typography a treatise on the processes of type-making the point system the names sizes
styles and prices of plain printing types (http books google com booksid=R4-DjphIpLMC) 2nd ed New York The Century Co p142ndash150
[13] Pasko Wesley Washington (1894) American dictionary of printing and bookmaking (http books google combooksid=Z_QUAAAAIAAJ) (1894) New York Howard Lockwood p 521
[14] Rowlett Russ (2005) How Many A Dictionary of Units of Measurement (http www unc edu ~rowlett units index html)[15] Thompson A and Taylor BN (2008) Guide for the Use of the International System of Units (SI) National Institute of Standards and
Technology Special Publication 811 p 57[16] US Code of Federal Regulations Title 21 Section 1019 Paragraph (b)(5)(viii) (http ecfr gpoaccess gov cgi t text text-idxc=ecframp
rgn=div8amp view=textamp node=212 0 1 1 2 1 1 6amp idno=21) retrieved August 29 2009[17] Barry N Taylor Ed NIST Special Publication 330 The International System of Units (SI) (http physics nist gov Pubs SP330 sp330
pdf) (2001 Edition) Washington US Government Printing Office 43The 12th Conference Generale des Poids et Mesures(CGPM)hellipdeclares that the word ldquolitrerdquo may be employed as a special name for the cubic decimetre
[18] CODATA Value atomic uint of mass (http physics nist gov cgi-bin cuu Valuettme|search_for=atomic+ unit+ of+ mass) (2006)National Institute of Standards and Technology Retrieved 16 September 2008
[19] The Swiss Federal Office for Metrology gives Zentner on a German language web page (http www metas ch de scales systemch html)and quintal on the English translation of that page (http www metas ch en scales systemch html) the unit is marked speacutecifiquementsuisse
[20] Pedersen O (1983) Glossary in Coyne G Hoskin M and Pedersen O Gregorian Reform of the Calendar Proceedings of the VaticanConference to Commemorate its 400th Anniversary Vatican Observatory Available from Astrophysics Data System
[21] Richards EG (1998) Mapping Time Oxford University Press pp 94ndash95 ISBN 0-19-850413-6[22] Steel Duncan (2000) Marking Time John Wiley amp Sons p 46 ISBN 0-471-29827-1[23] CODATA Value atomic unit of force (http physics nist gov cuu Constants ) (2006) National Institute of Standards and Technology
Retrieved September 14 2008[24] [[Comiteacute International des Poids et Mesures (http www bipm org en CIPM db 1946 2 )] Resolution 2] 1946 retrieved August 26
2009[25] Barry N Taylor (April 1995) Guide for the Use of the International System of Units (SI) (http physics nist gov cuu pdf sp811 pdf)
(NIST Special Publication 811) Washington DC US Government Printing Office pp 57ndash68[26] Barry N Taylor (April 1995) Guide for the Use of the International System of Units (SI) (NIST Special Publication 811) Washington DC
US Government Printing Office p 5[27] International System of Units (http www bipm org en si si_brochure chapter4 table7 html) 8th ed (2006) Bureau International des
Poids et Mesures Section 41 Table 7[28] The NIST Reference on Constants Units and Uncertainty (http physics nist gov cgi-bin cuu Valueauedm) 2006 retrieved August
26 2009[29] NIST Guide to SI Units Appendix B9 (http physics nist gov Pubs SP811 appenB9 html) retrieved August 27 2009[30] Standard for the Use of the International System of Units (SI) The Modern Metric System IEEEASTM SI 10-1997 (1997) New York and
West Conshohocken PA Institute of Electrical and Electronics Engineers and American Society for Testing and Materials Tables A1through A5
Conversion of units 29
[31] The NIST Reference on Constants Units and Uncertainty (http physics nist gov cuu Units candela html) retrieved August 28 2009[32] Ambler Thompson amp Barry N Taylor (2008) Guide for the Use of the International System of Units (SI) (http physics nist gov cuu
pdf sp811 pdf) Special Publication 811 Gaithersburg MD National Institute of Standards and Technology p 10[33] The International System of Units Section 222 Table 3 (http www bipm org en si si_brochure chapter2 2-2 table3 html) (8 ed)
Bureau International des Poids et Mesures 2006 retrieved August 27 2009[34] The NIST Guide to the SI (Special Publication 811) section 52 (http physics nist gov Pubs SP811 sec05 html5 2) 2008 retrieved
August 27 2009[35] Ambler Thompson amp Barry N Taylor (2008) Guide for the Use of the International System of Units (SI) (http physics nist gov cuu
pdf sp811 pdf) Special Publication 811 Gaithersburg MD National Institute of Standards and Technology p 5[36] [[Comiteacute international des poids et mesures (http www bipm org en CIPM db 2002 2 )] 2002 Recommendation 2] retrieved
August 27 2009[37] http converter mozdev org[38] http www xyntec com converber htm[39] http www calculla com[40] http illusions hu index phptask=100amp lang=0amp statpage=86[41] http www uniteasy com[42] http www tenderwire com wikipedialandingpage[43] http www kamlex com index phpoption=com_contentamp view=articleamp id=53amp Itemid=55[44] http www sttmedia com unitconverter[45] http www hmso gov uk si si1995 Uksi_19951804_en_2 htm[46] http www convertbuster com[47] http www unc edu ~rowlett units[48] http physics nist gov cuu Document nonsi_in_1998 pdf[49] http physics nist gov Pubs SP811 appenB9 html[50] http www onlineconversion com[51] http aurora rg iupui edu ~schadow units UCUM ucum html[52] http www posc org refs poscUnits20 xml[53] http www imperialtometric com[54] http www tampile com
Article Sources and Contributors 30
Article Sources and ContributorsConversion of units Source httpenwikipediaorgwindexphpoldid=373975089 Contributors 1571781xxx 7 A-giau AVSI Acather96 Ahoerstemeier Alexius08 Altenmann AndreEngels Andrewa Andy120290 Anonymi Ariconte Army1987 ArnoldReinhold Arthur3030 Aspects AxelBoldt AzaToth Azikala BW95 Bdesham Beland Bensaccount Bkumartvm Blackand White BlaiseFEgan BlueEarth Bobblewik Borbrav Bpmullins Bryan Derksen C J B Scholten CORNELIUSSEON CTZMSC3 Calltech Camerajohn Chaosfeary Charles MatthewsChris the speller Cmdrjameson Colonies Chris Conversion script Cope555 Crappy13 Crissov CyrilB DARTH SIDIOUS 2 DMacks DanielCD Dark Formal DarkestSideX DekisugiDenelson83 Dhp1080 Dicklyon DirkvdM Donald Duck Donarreiskoffer Dramatic Dyss DAringsbquougosz Egil Ehrenkater Ejohnsonboulder Elexmax Elf Emokhberi Enon Eob Epbr123Euchiasmus Fathead99 Father Goose Fella22 Femto FernandoAC Fibula Flutefreek Fred Bauder Fredrik Fuhghettaboutit Fuzheado Gaff Gene Nygaard Georgiy1996 Gerry AshtonGiftlite Gilliam Glenn L GoingBatty Goobergunch Gregsexton Greyengine5 Grunt Gurch Gutza HLHJ Haemo Hammersbach Heracles31 Herbee Heron HikerBush Hqb IcairnsIgiffin Indefatigable Isis JBobbitt JHunterJ Jabowery JakeVortex Jamicanmonkey Jason Begin Jay Jc3s5h Jcronen1 Jdoherty Jeffz1 Jeronimo Jimmuhk Jimp Jimwilliams57 JoeinwapJohndburger Josh Parris Jq4bagiq Kaihsu KaneWang Keenan Pepper Kevin Rector KeyStorm Khukri Kurtan Lee Daniel Crocker LightYear Linuxoidoz Liv4christ210 Loggie Lolo252Lupinelawyer M ichaeligl MJCdetroit MTC Mac MacMcF Magore Markus Kuhn Masterqwe MaxHund Maxamegalon2000 Mbeychok Meggar Mh26 Michael Daly Michael Hardy MichelAudy Mikelifeguard Mikhailov Kusserow Mindbuilder Missvain Monger Mr bulow MrOllie MrZhuKeeper Muro de Aguas Mwanner Mwtoews Nandesuka Natkeeran Ndsg NgjaimeNhy67ygv Nick Y Nick123 NickPenguin Ninjagecko Noe Nosilleg Now3r3 Obelix homologator Oldadamml Oleg Alexandrov Olivier Ortolan88 OwenBlacker Pac72 PassargeaPatrick Paul Martin Peter Horn Physchim62 Piels Pierdm Pmanderson Prometheus235 Quadell QuantumEleven Quod erat demonstrandum 314159 Radagast83 Rccoms RedWolfReinyday Revipm Rexparry sydney Reyk Rhetth Rhialto Rich Farmbrough Richard Myers Rjwilmsi Rlsheehan Robin Barry RoySmith Rpwolfgram SD6-Agent SGBailey SamuelLowry Samw Sander123 Seabhcan SebastianHelm Sherbert1 Shinhan Shrew Sietse Snel SimonP Sinbaddasail0r Skotte Smalljim SomeHuman Spencer Srleffler StarwarsmastergeekSteacoon StefanK SteveRamone Stevertigo Stokerm Suisui Sunev Superboy112233 Superm401 Synchronism Tacoman1996 Tarquin Taw Teratornis The Man in Question ThierrycThingg Thinking of England Thunderbird2 Timwi Tobias Hoevekamp Tomasr Tonsofpcs Toon05 Topsykretts2512 Trekphiler Tuwile Twanvl Uday147502 Unitman00 UrhixidurUtherSRG Vargenau Vsmith WarrenPlatts Wasell Welsh Whispering Wikinger Wolfkeeper Wtmitchell XJamRastafire Xenonice Yath Zginder Zibem Zocky Zotel 713 anonymousedits
poise (cgs unit) P equiv 10minus1 Pamiddots = 01 Pamiddots
pound per foot hour lb(ftmiddoth) equiv 1 lb(ftmiddoth) asymp 4133 789 times 10minus4 Pamiddots
pound per foot second lb(ftmiddots) equiv 1 lb(ftmiddots) asymp 1488164 Pamiddots
pound-force second per square foot lbfmiddotsft2 equiv 1 lbfmiddotsft2 asymp 4788026 Pamiddots
pound-force second per square inch lbfmiddotsin2 equiv 1 lbfmiddotsin2 asymp 6894757 Pamiddots
Conversion of units 21
Kinematic viscosity
Kinematic viscosity
Name of unit Symbol Definition Relation to SI units
square foot per second ft2s equiv 1 ft2s = 009290304 m2s
square metre per second (SI unit) m2s equiv 1 m2s = 1 m2s
stokes (cgs unit) St equiv10minus4 m2s
= 10minus4 m2s
Electric current
Electric current
Name of unit Symbol Definition Relation to SI units
ampere (SI base unit) A equiv The constant current needed to produce a force of 2 times 10minus7 newton per metre betweentwo straight parallel conductors of infinite length and negligible circular cross-sectionplaced one metre apart in a vacuum[8]
= 1 A
electromagnetic unitabampere (cgs unit)
abamp equiv 10 A = 10 A
esu per secondstatampere (cgs unit)
esus equiv (01 Amiddotms) c asymp3335641 times 10minus10 A
Electric charge
Electric charge
Name of unit Symbol Definition Relation to SI units
abcoulomb electromagnetic unit (cgsunit)
abC emu equiv 10 C = 10 C
atomic unit of charge au equiv e asymp 1602 176462 times 10minus19 C
coulomb (SI unit) C equiv The amount of electricity carried in one second of time by oneampere of current[24]
= 1 C = 1 Amiddots
faraday F equiv 1 mol times NAmiddote asymp 96 4853383 C
statcoulomb franklin electrostatic unit(cgs unit)
statC Fresu
equiv (01 Amiddotm) c asymp 3335 641 times 10minus10 C
Conversion of units 22
Electric dipole
Electric dipole
Name of unit Symbol Definition Relation to SI units
atomic unit of electric dipole moment ea0 asymp 8478 352 81 times 10minus30
Cmiddotm[28]
Electromotive force electric potential difference
Voltage electromotive force
Name ofunit
Symbol Definition Relation to SI units
abvolt (cgsunit)
abV equiv 1 times 10minus8 V = 1 times 10minus8 V
statvolt (cgsunit)
statV equiv cmiddot (1 μJAmiddotm) = 299792 458 V
volt (SIunit)
V The difference in electric potential across two points along a conducting wire carrying one ampereof constant current when the power dissipated between the points equals one watt[24]
= 1 V = 1 WA = 1kgmiddotm2(Amiddots3)
Electrical resistance
Electrical resistance
Name ofunit
Symbol Definition Relation to SI units
ohm (SIunit)
Ω The resistance between two points in a conductor when one volt of electric potential differenceapplied to these points produces one ampere of current in the conductor[24]
= 1 Ω = 1 VA = 1kgmiddotm2(A2middots3)
Capacitance
Capacitors ability to store charge
Name ofunit
Symbol Definition Relation to SI units
farad (SIunit)
F The capacitance between two parallel plates that results in one volt of potential difference whencharged by one coulomb of electricity[24]
= 1 F = 1 CV = 1A2middots4(kgmiddotm2)
Conversion of units 23
Magnetic flux
magnetic flux
Name of unit Symbol Definition Relation to SI units
maxwell (CGSunit)
Mx equiv 10minus8 Wb[29] = 1 times 10minus8 Wb
weber (SIunit)
Wb Magnetic flux which linking a circuit of one turn would produce in it an electromotive force of1 volt if it were reduced to zero at a uniform rate in 1 second[24]
= 1 Wb = 1 Vmiddots = 1kgmiddotm2(Amiddots2)
Magnetic flux density
What physicists call Magnetic field is called Magnetic flux density by electrical engineersand magnetic induction by applied mathematicians and electrical engineers
Name of unit Symbol Definition Relation to SI units
gauss (CGS unit) G equiv Mxcm2 = 10minus4
T= 1 times 10minus4 T [30]
tesla (SI unit) T equiv Wbm2 = 1 T = 1 Wbm2 = 1kg(Amiddots2)
Inductance
Inductance
Name ofunit
Symbol Definition Relation to SI units
henry (SIunit)
H The inductance of a closed circuit that produces one volt of electromotive force when the current inthe circuit varies at a uniform rate of one ampere per second[24]
= 1 H = 1 WbA = 1kgmiddotm2(Amiddots)2
Temperature
Temperature
Name of unit Symbol Definition Conversion to kelvin
degree Celsius degC degC equiv K minus 27315 [K] equiv [degC] + 27315
degree Delisle degDe [K] = 37315 minus [degDe] times 23
degree Fahrenheit degF degF equiv degC times 95 + 32 [K] equiv ([degF] + 45967) times 59
degree Newton degN [K] = [degN] times 10033 + 27315
degree Rankine degR degRa degR equiv K times 95 [K] equiv [degR] times 59
degree Reacuteaumur degReacute [K] = [degReacute] times 54 + 27315
degree Roslashmer degRoslash [K] = ([degRoslash] minus 75) times 4021 + 27315
kelvin (SI baseunit)
K equiv 127316 of the thermodynamic temperature of the triple point of water[8] equiv 1 K
Conversion of units 24
Information entropy
Information entropy
Name of unit Symbol Definition Relation to SI units Relation to bits
SI unit JK equiv JK = 1 JK
nat nip nepit nat equiv kB = 1380 650 5(23) times 10minus23 JK
bit shannon bit b Sh equiv ln(2) times kB = 9569 940 (16) times 10minus24 JK = 1 bit
ban hartley ban Hart equiv ln(10) times kB = 3179 065 3(53) times 10minus23 JK
nibble equiv 4 bits = 3827 976 0(64) times 10minus23 JK = 22 bit
byte B equiv 8 bits = 7655 952 (13) times 10minus23 JK = 23 bit
kilobyte (decimal) kB equiv 1 000 B = 7655 952 (13) times 10minus20 JK
kilobyte (kibibyte) KB KiB equiv 1 024 B = 7839 695 (13) times 10minus20 JK = 210 bit
Often information entropy is measured in shannons whereas the (discrete) storage space of digital devices ismeasured in bits Thus uncompressed redundant data occupy more than one bit of storage per shannon ofinformation entropy The multiples of a bit listed above are usually used with this meaning Other times the bit isused as a measure of information entropy and is thus a synonym of shannon
Luminous intensityThe candela is the preferred nomenclature for the SI unit
Luminous intensity
Name of unit Symbol Definition Relation toSI units
candela (SI baseunit) candle
cd The luminous intensity in a given direction of a source that emits monochromatic radiation offrequency 540 times 1012 hertz and that has a radiant intensity in that direction of 1683 watt persteradian[8]
= 1 cd
candlepower (new) cp equiv cd The use of candlepower as a unit is discouraged due to its ambiguity = 1 cd
candlepower (oldpre-1948)
cp Varies and is poorly reproducible[31] Approximately 0981 cd[14] asymp 0981 cd
Luminance
Conversion of units 25
Luminance
Name of unit Symbol Definition Relation to SI units
candela per square foot cdft2 equiv cdft2 asymp10763910417 cdm2
candela per square inch cdin2 equiv cdin2 asymp 15500031 cdm2
candela per square metre (SI unit) nit (deprecated[14] ) cdm2 equiv cdm2 = 1 cdm2
Name of unit Symbol Definition Relation to SI units
lumen (SIunit)
lm equiv cdmiddotsr = 1 lm = 1 cdmiddotsr
Illuminance
Illuminance
Name of unit Symbol Definition Relation to SI units
footcandle lumen per square foot fc equiv lmft2 = 10763910417 lx
lumen per square inch lmin2 equiv lmin2 asymp 15500031 lx
lux (SI unit) lx equiv lmm2 = 1 lx = 1 lmm2
phot (CGS unit) ph equiv lmcm2 = 1 times 104 lx
Radiation - source activity
Conversion of units 26
Radioactivity
Name of unit Symbol Definition Relation to SI units
becquerel (SIunit)
Bq equiv Number of disintegrations per second = 1 Bq = 1s
curie Ci equiv 37 times 1010 Bq = 37 times 1010 Bq [32]
rutherford (H) rd equiv 1 MBq = 1 times 106 Bq
Please note that although becquerel (Bq) and hertz (Hz) both ultimately refer to the same SI base unit (sminus1) Hz isused only for periodic phenomena and Bq is only used for stochastic processes associated with radioactivity[33]
Radiation - exposure
Radiation - exposure
Name of unit Symbol Definition Relation to SI units
roentgen R 1 R equiv 258 times 10minus4 Ckg[29] = 258 times 10minus4 Ckg
The roentgen is not a SI unit and the NIST strongly discourages its continued use[34]
Radiation - absorbed dose
Radiation - absorbed dose
Name of unit Symbol Definition Relation to SI units
Name of unit Symbol Definition Relation to SI units
Roumlntgen equivalent man rem equiv 001 Sv = 001 Sv
sievert (SI unit) Sv equiv 1 Jkg[33] = 1 Sv
Although the definitions for sievert (Sv) and gray (Gy) would seem to indicate that they measure the same quantitiesthis is not the case The effect of receiving a certain dose of radiation (given as Gy) is variable and depends on manyfactors thus a new unit was needed to denote the biological effectiveness of that dose on the body this is known asthe equivalent dose and is shown in Sv The general relationship between absorbed dose and equivalent dose can berepresented as
H = Q middot D
where H is the equivalent dose D is the absorbed dose and Q is a dimensionless quality factor Thus for anyquantity of D measured in Gy the numerical value for H measured in Sv may be different[36]
Conversion of units 27
Software toolsHome and office computers come with converters in bundled spreadsheet applications or can access free convertersvia the Internet Units and measurements can be easily converted using these tools but only if the units are explicitlydefined and the conversion is compatible (eg cmHg to kPa)
Free conversion softwarebull Units (software) a popular cross-platform command-line utilitybull Converter [37] contextual unit converter for Mozilla Firefox browsersbull Converber [38] portable application converting utilitybull calculla [39] calculla - online web convertersbull iMetrix [40] - unit converter for xpbull uniteasy [41] online scientific unit conversionbull Unit Converter Add-in for Excel [42] - allow a large selection of unit conversions within the Microsoft Excel
spread sheet programbull Unit Converter [43] simple and extensible unit converterbull Portable Unit Converter [44] including 4500 units 33 unit-categories and the possibility to create custom units
General commercial sources of convertersbull Advanced electronic calculators have unit-conversion functionalitybull Spreadsheet programs usually provide conversion functions or formulas or the user can write their ownbull Commercial mathematical scientific and technical applications often include converters
See also
bull Accuracy and precisionbull English unitsbull False precisionbull Imperial unitsbull International System of Unitsbull Mesures usuellesbull Metric system
bull Natural unitsbull Roundingbull Significant figuresbull Temperature conversionbull United States customary unitsbull Units conversion by factor-labelbull Units of measurement
External linksbull British law Units of measurement regulations 1995 [45]
bull ConvertBuster [46] Variety of conversion tools to convert easilybull How Many A dictionary of units of measurement [47]
bull NIST Fundamental physical constants mdash Non-SI units [48]PDF (357 KB)bull NIST Guide to SI Units [49] Many conversion factors listedbull Online Conversion Calculators [50] Very extensive list of conversions from-to equvalent unitsbull The Unified Code for Units of Measure [51]
bull Units Symbols and Conversions XML Dictionary [52]
bull Multilingual Online Conversion of Units [53]
bull Temperature Converter [54]
Conversion of units 28
References[1] United States Naval Observatory (2009) Selected Astronomical Constants 2009 (http asa usno navy mil SecK 2009
Astronomical_Constants_2009 txt) Accessed May 10 2009[2] NIST Reference on Constants Units and Uncertainty (http physics nist gov cgi-bin cuu Valuebohrrada0|search_for=Bohr+
radius)(2006) National Institute of Standards and Technology Retrieved February 22 2008[3] National Institute of Standards and Technology General Tables of Units of Measurement (http ts nist gov WeightsAndMeasures
Publications appxc cfm)[4] Lide D (Ed) (1990) Handbook of Chemistry and Physics (71st ed) Boca Raton FL CRC Press Section 1[5] National Bureau of Standards (June 30 1959) Refinement of values for the yard and the pound Federal Register viewed September 20
2006 at National Geodetic Survey web site (http www ngs noaa gov PUBS_LIB FedRegister FRdoc59-5442 pdf)[6] The International Astronomical Union and Astronomical Units (http www iau org public_press themes measuring )[7] Klein Herbert Arthur (1988) The Science of Measurement a Historical Survey Mineola NY Dover Publications 0-4862-5839-4[8] The International System of Units Section 21 (http www bipm org en si si_brochure chapter2 2-1 ) (8 ed) Bureau International des
Poids et Mesures 2006 retrieved August 26 2009[9] International System of Units (http www bipm org en si si_brochure chapter4 table8 html) 8th ed (2006) Bureau International des
Poids et Mesures Section 41 Table 8[10] P Kenneth Seidelmann Ed (1992) Explanatory Supplement to the Astronomical Almanac Sausalito CA University Science Books p 716
and sv parsec in Glossary[11] Whitelaw Ian (2007) A Measure of All Things The Story of Man and Measurement (http books google com
booksid=3zgGEWM5-iAC) New York Macmillan 0-312-37026-1 p 152[12] De Vinne Theodore Low (1900) The practice of typography a treatise on the processes of type-making the point system the names sizes
styles and prices of plain printing types (http books google com booksid=R4-DjphIpLMC) 2nd ed New York The Century Co p142ndash150
[13] Pasko Wesley Washington (1894) American dictionary of printing and bookmaking (http books google combooksid=Z_QUAAAAIAAJ) (1894) New York Howard Lockwood p 521
[14] Rowlett Russ (2005) How Many A Dictionary of Units of Measurement (http www unc edu ~rowlett units index html)[15] Thompson A and Taylor BN (2008) Guide for the Use of the International System of Units (SI) National Institute of Standards and
Technology Special Publication 811 p 57[16] US Code of Federal Regulations Title 21 Section 1019 Paragraph (b)(5)(viii) (http ecfr gpoaccess gov cgi t text text-idxc=ecframp
rgn=div8amp view=textamp node=212 0 1 1 2 1 1 6amp idno=21) retrieved August 29 2009[17] Barry N Taylor Ed NIST Special Publication 330 The International System of Units (SI) (http physics nist gov Pubs SP330 sp330
pdf) (2001 Edition) Washington US Government Printing Office 43The 12th Conference Generale des Poids et Mesures(CGPM)hellipdeclares that the word ldquolitrerdquo may be employed as a special name for the cubic decimetre
[18] CODATA Value atomic uint of mass (http physics nist gov cgi-bin cuu Valuettme|search_for=atomic+ unit+ of+ mass) (2006)National Institute of Standards and Technology Retrieved 16 September 2008
[19] The Swiss Federal Office for Metrology gives Zentner on a German language web page (http www metas ch de scales systemch html)and quintal on the English translation of that page (http www metas ch en scales systemch html) the unit is marked speacutecifiquementsuisse
[20] Pedersen O (1983) Glossary in Coyne G Hoskin M and Pedersen O Gregorian Reform of the Calendar Proceedings of the VaticanConference to Commemorate its 400th Anniversary Vatican Observatory Available from Astrophysics Data System
[21] Richards EG (1998) Mapping Time Oxford University Press pp 94ndash95 ISBN 0-19-850413-6[22] Steel Duncan (2000) Marking Time John Wiley amp Sons p 46 ISBN 0-471-29827-1[23] CODATA Value atomic unit of force (http physics nist gov cuu Constants ) (2006) National Institute of Standards and Technology
Retrieved September 14 2008[24] [[Comiteacute International des Poids et Mesures (http www bipm org en CIPM db 1946 2 )] Resolution 2] 1946 retrieved August 26
2009[25] Barry N Taylor (April 1995) Guide for the Use of the International System of Units (SI) (http physics nist gov cuu pdf sp811 pdf)
(NIST Special Publication 811) Washington DC US Government Printing Office pp 57ndash68[26] Barry N Taylor (April 1995) Guide for the Use of the International System of Units (SI) (NIST Special Publication 811) Washington DC
US Government Printing Office p 5[27] International System of Units (http www bipm org en si si_brochure chapter4 table7 html) 8th ed (2006) Bureau International des
Poids et Mesures Section 41 Table 7[28] The NIST Reference on Constants Units and Uncertainty (http physics nist gov cgi-bin cuu Valueauedm) 2006 retrieved August
26 2009[29] NIST Guide to SI Units Appendix B9 (http physics nist gov Pubs SP811 appenB9 html) retrieved August 27 2009[30] Standard for the Use of the International System of Units (SI) The Modern Metric System IEEEASTM SI 10-1997 (1997) New York and
West Conshohocken PA Institute of Electrical and Electronics Engineers and American Society for Testing and Materials Tables A1through A5
Conversion of units 29
[31] The NIST Reference on Constants Units and Uncertainty (http physics nist gov cuu Units candela html) retrieved August 28 2009[32] Ambler Thompson amp Barry N Taylor (2008) Guide for the Use of the International System of Units (SI) (http physics nist gov cuu
pdf sp811 pdf) Special Publication 811 Gaithersburg MD National Institute of Standards and Technology p 10[33] The International System of Units Section 222 Table 3 (http www bipm org en si si_brochure chapter2 2-2 table3 html) (8 ed)
Bureau International des Poids et Mesures 2006 retrieved August 27 2009[34] The NIST Guide to the SI (Special Publication 811) section 52 (http physics nist gov Pubs SP811 sec05 html5 2) 2008 retrieved
August 27 2009[35] Ambler Thompson amp Barry N Taylor (2008) Guide for the Use of the International System of Units (SI) (http physics nist gov cuu
pdf sp811 pdf) Special Publication 811 Gaithersburg MD National Institute of Standards and Technology p 5[36] [[Comiteacute international des poids et mesures (http www bipm org en CIPM db 2002 2 )] 2002 Recommendation 2] retrieved
August 27 2009[37] http converter mozdev org[38] http www xyntec com converber htm[39] http www calculla com[40] http illusions hu index phptask=100amp lang=0amp statpage=86[41] http www uniteasy com[42] http www tenderwire com wikipedialandingpage[43] http www kamlex com index phpoption=com_contentamp view=articleamp id=53amp Itemid=55[44] http www sttmedia com unitconverter[45] http www hmso gov uk si si1995 Uksi_19951804_en_2 htm[46] http www convertbuster com[47] http www unc edu ~rowlett units[48] http physics nist gov cuu Document nonsi_in_1998 pdf[49] http physics nist gov Pubs SP811 appenB9 html[50] http www onlineconversion com[51] http aurora rg iupui edu ~schadow units UCUM ucum html[52] http www posc org refs poscUnits20 xml[53] http www imperialtometric com[54] http www tampile com
Article Sources and Contributors 30
Article Sources and ContributorsConversion of units Source httpenwikipediaorgwindexphpoldid=373975089 Contributors 1571781xxx 7 A-giau AVSI Acather96 Ahoerstemeier Alexius08 Altenmann AndreEngels Andrewa Andy120290 Anonymi Ariconte Army1987 ArnoldReinhold Arthur3030 Aspects AxelBoldt AzaToth Azikala BW95 Bdesham Beland Bensaccount Bkumartvm Blackand White BlaiseFEgan BlueEarth Bobblewik Borbrav Bpmullins Bryan Derksen C J B Scholten CORNELIUSSEON CTZMSC3 Calltech Camerajohn Chaosfeary Charles MatthewsChris the speller Cmdrjameson Colonies Chris Conversion script Cope555 Crappy13 Crissov CyrilB DARTH SIDIOUS 2 DMacks DanielCD Dark Formal DarkestSideX DekisugiDenelson83 Dhp1080 Dicklyon DirkvdM Donald Duck Donarreiskoffer Dramatic Dyss DAringsbquougosz Egil Ehrenkater Ejohnsonboulder Elexmax Elf Emokhberi Enon Eob Epbr123Euchiasmus Fathead99 Father Goose Fella22 Femto FernandoAC Fibula Flutefreek Fred Bauder Fredrik Fuhghettaboutit Fuzheado Gaff Gene Nygaard Georgiy1996 Gerry AshtonGiftlite Gilliam Glenn L GoingBatty Goobergunch Gregsexton Greyengine5 Grunt Gurch Gutza HLHJ Haemo Hammersbach Heracles31 Herbee Heron HikerBush Hqb IcairnsIgiffin Indefatigable Isis JBobbitt JHunterJ Jabowery JakeVortex Jamicanmonkey Jason Begin Jay Jc3s5h Jcronen1 Jdoherty Jeffz1 Jeronimo Jimmuhk Jimp Jimwilliams57 JoeinwapJohndburger Josh Parris Jq4bagiq Kaihsu KaneWang Keenan Pepper Kevin Rector KeyStorm Khukri Kurtan Lee Daniel Crocker LightYear Linuxoidoz Liv4christ210 Loggie Lolo252Lupinelawyer M ichaeligl MJCdetroit MTC Mac MacMcF Magore Markus Kuhn Masterqwe MaxHund Maxamegalon2000 Mbeychok Meggar Mh26 Michael Daly Michael Hardy MichelAudy Mikelifeguard Mikhailov Kusserow Mindbuilder Missvain Monger Mr bulow MrOllie MrZhuKeeper Muro de Aguas Mwanner Mwtoews Nandesuka Natkeeran Ndsg NgjaimeNhy67ygv Nick Y Nick123 NickPenguin Ninjagecko Noe Nosilleg Now3r3 Obelix homologator Oldadamml Oleg Alexandrov Olivier Ortolan88 OwenBlacker Pac72 PassargeaPatrick Paul Martin Peter Horn Physchim62 Piels Pierdm Pmanderson Prometheus235 Quadell QuantumEleven Quod erat demonstrandum 314159 Radagast83 Rccoms RedWolfReinyday Revipm Rexparry sydney Reyk Rhetth Rhialto Rich Farmbrough Richard Myers Rjwilmsi Rlsheehan Robin Barry RoySmith Rpwolfgram SD6-Agent SGBailey SamuelLowry Samw Sander123 Seabhcan SebastianHelm Sherbert1 Shinhan Shrew Sietse Snel SimonP Sinbaddasail0r Skotte Smalljim SomeHuman Spencer Srleffler StarwarsmastergeekSteacoon StefanK SteveRamone Stevertigo Stokerm Suisui Sunev Superboy112233 Superm401 Synchronism Tacoman1996 Tarquin Taw Teratornis The Man in Question ThierrycThingg Thinking of England Thunderbird2 Timwi Tobias Hoevekamp Tomasr Tonsofpcs Toon05 Topsykretts2512 Trekphiler Tuwile Twanvl Uday147502 Unitman00 UrhixidurUtherSRG Vargenau Vsmith WarrenPlatts Wasell Welsh Whispering Wikinger Wolfkeeper Wtmitchell XJamRastafire Xenonice Yath Zginder Zibem Zocky Zotel 713 anonymousedits
poise (cgs unit) P equiv 10minus1 Pamiddots = 01 Pamiddots
pound per foot hour lb(ftmiddoth) equiv 1 lb(ftmiddoth) asymp 4133 789 times 10minus4 Pamiddots
pound per foot second lb(ftmiddots) equiv 1 lb(ftmiddots) asymp 1488164 Pamiddots
pound-force second per square foot lbfmiddotsft2 equiv 1 lbfmiddotsft2 asymp 4788026 Pamiddots
pound-force second per square inch lbfmiddotsin2 equiv 1 lbfmiddotsin2 asymp 6894757 Pamiddots
Conversion of units 21
Kinematic viscosity
Kinematic viscosity
Name of unit Symbol Definition Relation to SI units
square foot per second ft2s equiv 1 ft2s = 009290304 m2s
square metre per second (SI unit) m2s equiv 1 m2s = 1 m2s
stokes (cgs unit) St equiv10minus4 m2s
= 10minus4 m2s
Electric current
Electric current
Name of unit Symbol Definition Relation to SI units
ampere (SI base unit) A equiv The constant current needed to produce a force of 2 times 10minus7 newton per metre betweentwo straight parallel conductors of infinite length and negligible circular cross-sectionplaced one metre apart in a vacuum[8]
= 1 A
electromagnetic unitabampere (cgs unit)
abamp equiv 10 A = 10 A
esu per secondstatampere (cgs unit)
esus equiv (01 Amiddotms) c asymp3335641 times 10minus10 A
Electric charge
Electric charge
Name of unit Symbol Definition Relation to SI units
abcoulomb electromagnetic unit (cgsunit)
abC emu equiv 10 C = 10 C
atomic unit of charge au equiv e asymp 1602 176462 times 10minus19 C
coulomb (SI unit) C equiv The amount of electricity carried in one second of time by oneampere of current[24]
= 1 C = 1 Amiddots
faraday F equiv 1 mol times NAmiddote asymp 96 4853383 C
statcoulomb franklin electrostatic unit(cgs unit)
statC Fresu
equiv (01 Amiddotm) c asymp 3335 641 times 10minus10 C
Conversion of units 22
Electric dipole
Electric dipole
Name of unit Symbol Definition Relation to SI units
atomic unit of electric dipole moment ea0 asymp 8478 352 81 times 10minus30
Cmiddotm[28]
Electromotive force electric potential difference
Voltage electromotive force
Name ofunit
Symbol Definition Relation to SI units
abvolt (cgsunit)
abV equiv 1 times 10minus8 V = 1 times 10minus8 V
statvolt (cgsunit)
statV equiv cmiddot (1 μJAmiddotm) = 299792 458 V
volt (SIunit)
V The difference in electric potential across two points along a conducting wire carrying one ampereof constant current when the power dissipated between the points equals one watt[24]
= 1 V = 1 WA = 1kgmiddotm2(Amiddots3)
Electrical resistance
Electrical resistance
Name ofunit
Symbol Definition Relation to SI units
ohm (SIunit)
Ω The resistance between two points in a conductor when one volt of electric potential differenceapplied to these points produces one ampere of current in the conductor[24]
= 1 Ω = 1 VA = 1kgmiddotm2(A2middots3)
Capacitance
Capacitors ability to store charge
Name ofunit
Symbol Definition Relation to SI units
farad (SIunit)
F The capacitance between two parallel plates that results in one volt of potential difference whencharged by one coulomb of electricity[24]
= 1 F = 1 CV = 1A2middots4(kgmiddotm2)
Conversion of units 23
Magnetic flux
magnetic flux
Name of unit Symbol Definition Relation to SI units
maxwell (CGSunit)
Mx equiv 10minus8 Wb[29] = 1 times 10minus8 Wb
weber (SIunit)
Wb Magnetic flux which linking a circuit of one turn would produce in it an electromotive force of1 volt if it were reduced to zero at a uniform rate in 1 second[24]
= 1 Wb = 1 Vmiddots = 1kgmiddotm2(Amiddots2)
Magnetic flux density
What physicists call Magnetic field is called Magnetic flux density by electrical engineersand magnetic induction by applied mathematicians and electrical engineers
Name of unit Symbol Definition Relation to SI units
gauss (CGS unit) G equiv Mxcm2 = 10minus4
T= 1 times 10minus4 T [30]
tesla (SI unit) T equiv Wbm2 = 1 T = 1 Wbm2 = 1kg(Amiddots2)
Inductance
Inductance
Name ofunit
Symbol Definition Relation to SI units
henry (SIunit)
H The inductance of a closed circuit that produces one volt of electromotive force when the current inthe circuit varies at a uniform rate of one ampere per second[24]
= 1 H = 1 WbA = 1kgmiddotm2(Amiddots)2
Temperature
Temperature
Name of unit Symbol Definition Conversion to kelvin
degree Celsius degC degC equiv K minus 27315 [K] equiv [degC] + 27315
degree Delisle degDe [K] = 37315 minus [degDe] times 23
degree Fahrenheit degF degF equiv degC times 95 + 32 [K] equiv ([degF] + 45967) times 59
degree Newton degN [K] = [degN] times 10033 + 27315
degree Rankine degR degRa degR equiv K times 95 [K] equiv [degR] times 59
degree Reacuteaumur degReacute [K] = [degReacute] times 54 + 27315
degree Roslashmer degRoslash [K] = ([degRoslash] minus 75) times 4021 + 27315
kelvin (SI baseunit)
K equiv 127316 of the thermodynamic temperature of the triple point of water[8] equiv 1 K
Conversion of units 24
Information entropy
Information entropy
Name of unit Symbol Definition Relation to SI units Relation to bits
SI unit JK equiv JK = 1 JK
nat nip nepit nat equiv kB = 1380 650 5(23) times 10minus23 JK
bit shannon bit b Sh equiv ln(2) times kB = 9569 940 (16) times 10minus24 JK = 1 bit
ban hartley ban Hart equiv ln(10) times kB = 3179 065 3(53) times 10minus23 JK
nibble equiv 4 bits = 3827 976 0(64) times 10minus23 JK = 22 bit
byte B equiv 8 bits = 7655 952 (13) times 10minus23 JK = 23 bit
kilobyte (decimal) kB equiv 1 000 B = 7655 952 (13) times 10minus20 JK
kilobyte (kibibyte) KB KiB equiv 1 024 B = 7839 695 (13) times 10minus20 JK = 210 bit
Often information entropy is measured in shannons whereas the (discrete) storage space of digital devices ismeasured in bits Thus uncompressed redundant data occupy more than one bit of storage per shannon ofinformation entropy The multiples of a bit listed above are usually used with this meaning Other times the bit isused as a measure of information entropy and is thus a synonym of shannon
Luminous intensityThe candela is the preferred nomenclature for the SI unit
Luminous intensity
Name of unit Symbol Definition Relation toSI units
candela (SI baseunit) candle
cd The luminous intensity in a given direction of a source that emits monochromatic radiation offrequency 540 times 1012 hertz and that has a radiant intensity in that direction of 1683 watt persteradian[8]
= 1 cd
candlepower (new) cp equiv cd The use of candlepower as a unit is discouraged due to its ambiguity = 1 cd
candlepower (oldpre-1948)
cp Varies and is poorly reproducible[31] Approximately 0981 cd[14] asymp 0981 cd
Luminance
Conversion of units 25
Luminance
Name of unit Symbol Definition Relation to SI units
candela per square foot cdft2 equiv cdft2 asymp10763910417 cdm2
candela per square inch cdin2 equiv cdin2 asymp 15500031 cdm2
candela per square metre (SI unit) nit (deprecated[14] ) cdm2 equiv cdm2 = 1 cdm2
Name of unit Symbol Definition Relation to SI units
lumen (SIunit)
lm equiv cdmiddotsr = 1 lm = 1 cdmiddotsr
Illuminance
Illuminance
Name of unit Symbol Definition Relation to SI units
footcandle lumen per square foot fc equiv lmft2 = 10763910417 lx
lumen per square inch lmin2 equiv lmin2 asymp 15500031 lx
lux (SI unit) lx equiv lmm2 = 1 lx = 1 lmm2
phot (CGS unit) ph equiv lmcm2 = 1 times 104 lx
Radiation - source activity
Conversion of units 26
Radioactivity
Name of unit Symbol Definition Relation to SI units
becquerel (SIunit)
Bq equiv Number of disintegrations per second = 1 Bq = 1s
curie Ci equiv 37 times 1010 Bq = 37 times 1010 Bq [32]
rutherford (H) rd equiv 1 MBq = 1 times 106 Bq
Please note that although becquerel (Bq) and hertz (Hz) both ultimately refer to the same SI base unit (sminus1) Hz isused only for periodic phenomena and Bq is only used for stochastic processes associated with radioactivity[33]
Radiation - exposure
Radiation - exposure
Name of unit Symbol Definition Relation to SI units
roentgen R 1 R equiv 258 times 10minus4 Ckg[29] = 258 times 10minus4 Ckg
The roentgen is not a SI unit and the NIST strongly discourages its continued use[34]
Radiation - absorbed dose
Radiation - absorbed dose
Name of unit Symbol Definition Relation to SI units
Name of unit Symbol Definition Relation to SI units
Roumlntgen equivalent man rem equiv 001 Sv = 001 Sv
sievert (SI unit) Sv equiv 1 Jkg[33] = 1 Sv
Although the definitions for sievert (Sv) and gray (Gy) would seem to indicate that they measure the same quantitiesthis is not the case The effect of receiving a certain dose of radiation (given as Gy) is variable and depends on manyfactors thus a new unit was needed to denote the biological effectiveness of that dose on the body this is known asthe equivalent dose and is shown in Sv The general relationship between absorbed dose and equivalent dose can berepresented as
H = Q middot D
where H is the equivalent dose D is the absorbed dose and Q is a dimensionless quality factor Thus for anyquantity of D measured in Gy the numerical value for H measured in Sv may be different[36]
Conversion of units 27
Software toolsHome and office computers come with converters in bundled spreadsheet applications or can access free convertersvia the Internet Units and measurements can be easily converted using these tools but only if the units are explicitlydefined and the conversion is compatible (eg cmHg to kPa)
Free conversion softwarebull Units (software) a popular cross-platform command-line utilitybull Converter [37] contextual unit converter for Mozilla Firefox browsersbull Converber [38] portable application converting utilitybull calculla [39] calculla - online web convertersbull iMetrix [40] - unit converter for xpbull uniteasy [41] online scientific unit conversionbull Unit Converter Add-in for Excel [42] - allow a large selection of unit conversions within the Microsoft Excel
spread sheet programbull Unit Converter [43] simple and extensible unit converterbull Portable Unit Converter [44] including 4500 units 33 unit-categories and the possibility to create custom units
General commercial sources of convertersbull Advanced electronic calculators have unit-conversion functionalitybull Spreadsheet programs usually provide conversion functions or formulas or the user can write their ownbull Commercial mathematical scientific and technical applications often include converters
See also
bull Accuracy and precisionbull English unitsbull False precisionbull Imperial unitsbull International System of Unitsbull Mesures usuellesbull Metric system
bull Natural unitsbull Roundingbull Significant figuresbull Temperature conversionbull United States customary unitsbull Units conversion by factor-labelbull Units of measurement
External linksbull British law Units of measurement regulations 1995 [45]
bull ConvertBuster [46] Variety of conversion tools to convert easilybull How Many A dictionary of units of measurement [47]
bull NIST Fundamental physical constants mdash Non-SI units [48]PDF (357 KB)bull NIST Guide to SI Units [49] Many conversion factors listedbull Online Conversion Calculators [50] Very extensive list of conversions from-to equvalent unitsbull The Unified Code for Units of Measure [51]
bull Units Symbols and Conversions XML Dictionary [52]
bull Multilingual Online Conversion of Units [53]
bull Temperature Converter [54]
Conversion of units 28
References[1] United States Naval Observatory (2009) Selected Astronomical Constants 2009 (http asa usno navy mil SecK 2009
Astronomical_Constants_2009 txt) Accessed May 10 2009[2] NIST Reference on Constants Units and Uncertainty (http physics nist gov cgi-bin cuu Valuebohrrada0|search_for=Bohr+
radius)(2006) National Institute of Standards and Technology Retrieved February 22 2008[3] National Institute of Standards and Technology General Tables of Units of Measurement (http ts nist gov WeightsAndMeasures
Publications appxc cfm)[4] Lide D (Ed) (1990) Handbook of Chemistry and Physics (71st ed) Boca Raton FL CRC Press Section 1[5] National Bureau of Standards (June 30 1959) Refinement of values for the yard and the pound Federal Register viewed September 20
2006 at National Geodetic Survey web site (http www ngs noaa gov PUBS_LIB FedRegister FRdoc59-5442 pdf)[6] The International Astronomical Union and Astronomical Units (http www iau org public_press themes measuring )[7] Klein Herbert Arthur (1988) The Science of Measurement a Historical Survey Mineola NY Dover Publications 0-4862-5839-4[8] The International System of Units Section 21 (http www bipm org en si si_brochure chapter2 2-1 ) (8 ed) Bureau International des
Poids et Mesures 2006 retrieved August 26 2009[9] International System of Units (http www bipm org en si si_brochure chapter4 table8 html) 8th ed (2006) Bureau International des
Poids et Mesures Section 41 Table 8[10] P Kenneth Seidelmann Ed (1992) Explanatory Supplement to the Astronomical Almanac Sausalito CA University Science Books p 716
and sv parsec in Glossary[11] Whitelaw Ian (2007) A Measure of All Things The Story of Man and Measurement (http books google com
booksid=3zgGEWM5-iAC) New York Macmillan 0-312-37026-1 p 152[12] De Vinne Theodore Low (1900) The practice of typography a treatise on the processes of type-making the point system the names sizes
styles and prices of plain printing types (http books google com booksid=R4-DjphIpLMC) 2nd ed New York The Century Co p142ndash150
[13] Pasko Wesley Washington (1894) American dictionary of printing and bookmaking (http books google combooksid=Z_QUAAAAIAAJ) (1894) New York Howard Lockwood p 521
[14] Rowlett Russ (2005) How Many A Dictionary of Units of Measurement (http www unc edu ~rowlett units index html)[15] Thompson A and Taylor BN (2008) Guide for the Use of the International System of Units (SI) National Institute of Standards and
Technology Special Publication 811 p 57[16] US Code of Federal Regulations Title 21 Section 1019 Paragraph (b)(5)(viii) (http ecfr gpoaccess gov cgi t text text-idxc=ecframp
rgn=div8amp view=textamp node=212 0 1 1 2 1 1 6amp idno=21) retrieved August 29 2009[17] Barry N Taylor Ed NIST Special Publication 330 The International System of Units (SI) (http physics nist gov Pubs SP330 sp330
pdf) (2001 Edition) Washington US Government Printing Office 43The 12th Conference Generale des Poids et Mesures(CGPM)hellipdeclares that the word ldquolitrerdquo may be employed as a special name for the cubic decimetre
[18] CODATA Value atomic uint of mass (http physics nist gov cgi-bin cuu Valuettme|search_for=atomic+ unit+ of+ mass) (2006)National Institute of Standards and Technology Retrieved 16 September 2008
[19] The Swiss Federal Office for Metrology gives Zentner on a German language web page (http www metas ch de scales systemch html)and quintal on the English translation of that page (http www metas ch en scales systemch html) the unit is marked speacutecifiquementsuisse
[20] Pedersen O (1983) Glossary in Coyne G Hoskin M and Pedersen O Gregorian Reform of the Calendar Proceedings of the VaticanConference to Commemorate its 400th Anniversary Vatican Observatory Available from Astrophysics Data System
[21] Richards EG (1998) Mapping Time Oxford University Press pp 94ndash95 ISBN 0-19-850413-6[22] Steel Duncan (2000) Marking Time John Wiley amp Sons p 46 ISBN 0-471-29827-1[23] CODATA Value atomic unit of force (http physics nist gov cuu Constants ) (2006) National Institute of Standards and Technology
Retrieved September 14 2008[24] [[Comiteacute International des Poids et Mesures (http www bipm org en CIPM db 1946 2 )] Resolution 2] 1946 retrieved August 26
2009[25] Barry N Taylor (April 1995) Guide for the Use of the International System of Units (SI) (http physics nist gov cuu pdf sp811 pdf)
(NIST Special Publication 811) Washington DC US Government Printing Office pp 57ndash68[26] Barry N Taylor (April 1995) Guide for the Use of the International System of Units (SI) (NIST Special Publication 811) Washington DC
US Government Printing Office p 5[27] International System of Units (http www bipm org en si si_brochure chapter4 table7 html) 8th ed (2006) Bureau International des
Poids et Mesures Section 41 Table 7[28] The NIST Reference on Constants Units and Uncertainty (http physics nist gov cgi-bin cuu Valueauedm) 2006 retrieved August
26 2009[29] NIST Guide to SI Units Appendix B9 (http physics nist gov Pubs SP811 appenB9 html) retrieved August 27 2009[30] Standard for the Use of the International System of Units (SI) The Modern Metric System IEEEASTM SI 10-1997 (1997) New York and
West Conshohocken PA Institute of Electrical and Electronics Engineers and American Society for Testing and Materials Tables A1through A5
Conversion of units 29
[31] The NIST Reference on Constants Units and Uncertainty (http physics nist gov cuu Units candela html) retrieved August 28 2009[32] Ambler Thompson amp Barry N Taylor (2008) Guide for the Use of the International System of Units (SI) (http physics nist gov cuu
pdf sp811 pdf) Special Publication 811 Gaithersburg MD National Institute of Standards and Technology p 10[33] The International System of Units Section 222 Table 3 (http www bipm org en si si_brochure chapter2 2-2 table3 html) (8 ed)
Bureau International des Poids et Mesures 2006 retrieved August 27 2009[34] The NIST Guide to the SI (Special Publication 811) section 52 (http physics nist gov Pubs SP811 sec05 html5 2) 2008 retrieved
August 27 2009[35] Ambler Thompson amp Barry N Taylor (2008) Guide for the Use of the International System of Units (SI) (http physics nist gov cuu
pdf sp811 pdf) Special Publication 811 Gaithersburg MD National Institute of Standards and Technology p 5[36] [[Comiteacute international des poids et mesures (http www bipm org en CIPM db 2002 2 )] 2002 Recommendation 2] retrieved
August 27 2009[37] http converter mozdev org[38] http www xyntec com converber htm[39] http www calculla com[40] http illusions hu index phptask=100amp lang=0amp statpage=86[41] http www uniteasy com[42] http www tenderwire com wikipedialandingpage[43] http www kamlex com index phpoption=com_contentamp view=articleamp id=53amp Itemid=55[44] http www sttmedia com unitconverter[45] http www hmso gov uk si si1995 Uksi_19951804_en_2 htm[46] http www convertbuster com[47] http www unc edu ~rowlett units[48] http physics nist gov cuu Document nonsi_in_1998 pdf[49] http physics nist gov Pubs SP811 appenB9 html[50] http www onlineconversion com[51] http aurora rg iupui edu ~schadow units UCUM ucum html[52] http www posc org refs poscUnits20 xml[53] http www imperialtometric com[54] http www tampile com
Article Sources and Contributors 30
Article Sources and ContributorsConversion of units Source httpenwikipediaorgwindexphpoldid=373975089 Contributors 1571781xxx 7 A-giau AVSI Acather96 Ahoerstemeier Alexius08 Altenmann AndreEngels Andrewa Andy120290 Anonymi Ariconte Army1987 ArnoldReinhold Arthur3030 Aspects AxelBoldt AzaToth Azikala BW95 Bdesham Beland Bensaccount Bkumartvm Blackand White BlaiseFEgan BlueEarth Bobblewik Borbrav Bpmullins Bryan Derksen C J B Scholten CORNELIUSSEON CTZMSC3 Calltech Camerajohn Chaosfeary Charles MatthewsChris the speller Cmdrjameson Colonies Chris Conversion script Cope555 Crappy13 Crissov CyrilB DARTH SIDIOUS 2 DMacks DanielCD Dark Formal DarkestSideX DekisugiDenelson83 Dhp1080 Dicklyon DirkvdM Donald Duck Donarreiskoffer Dramatic Dyss DAringsbquougosz Egil Ehrenkater Ejohnsonboulder Elexmax Elf Emokhberi Enon Eob Epbr123Euchiasmus Fathead99 Father Goose Fella22 Femto FernandoAC Fibula Flutefreek Fred Bauder Fredrik Fuhghettaboutit Fuzheado Gaff Gene Nygaard Georgiy1996 Gerry AshtonGiftlite Gilliam Glenn L GoingBatty Goobergunch Gregsexton Greyengine5 Grunt Gurch Gutza HLHJ Haemo Hammersbach Heracles31 Herbee Heron HikerBush Hqb IcairnsIgiffin Indefatigable Isis JBobbitt JHunterJ Jabowery JakeVortex Jamicanmonkey Jason Begin Jay Jc3s5h Jcronen1 Jdoherty Jeffz1 Jeronimo Jimmuhk Jimp Jimwilliams57 JoeinwapJohndburger Josh Parris Jq4bagiq Kaihsu KaneWang Keenan Pepper Kevin Rector KeyStorm Khukri Kurtan Lee Daniel Crocker LightYear Linuxoidoz Liv4christ210 Loggie Lolo252Lupinelawyer M ichaeligl MJCdetroit MTC Mac MacMcF Magore Markus Kuhn Masterqwe MaxHund Maxamegalon2000 Mbeychok Meggar Mh26 Michael Daly Michael Hardy MichelAudy Mikelifeguard Mikhailov Kusserow Mindbuilder Missvain Monger Mr bulow MrOllie MrZhuKeeper Muro de Aguas Mwanner Mwtoews Nandesuka Natkeeran Ndsg NgjaimeNhy67ygv Nick Y Nick123 NickPenguin Ninjagecko Noe Nosilleg Now3r3 Obelix homologator Oldadamml Oleg Alexandrov Olivier Ortolan88 OwenBlacker Pac72 PassargeaPatrick Paul Martin Peter Horn Physchim62 Piels Pierdm Pmanderson Prometheus235 Quadell QuantumEleven Quod erat demonstrandum 314159 Radagast83 Rccoms RedWolfReinyday Revipm Rexparry sydney Reyk Rhetth Rhialto Rich Farmbrough Richard Myers Rjwilmsi Rlsheehan Robin Barry RoySmith Rpwolfgram SD6-Agent SGBailey SamuelLowry Samw Sander123 Seabhcan SebastianHelm Sherbert1 Shinhan Shrew Sietse Snel SimonP Sinbaddasail0r Skotte Smalljim SomeHuman Spencer Srleffler StarwarsmastergeekSteacoon StefanK SteveRamone Stevertigo Stokerm Suisui Sunev Superboy112233 Superm401 Synchronism Tacoman1996 Tarquin Taw Teratornis The Man in Question ThierrycThingg Thinking of England Thunderbird2 Timwi Tobias Hoevekamp Tomasr Tonsofpcs Toon05 Topsykretts2512 Trekphiler Tuwile Twanvl Uday147502 Unitman00 UrhixidurUtherSRG Vargenau Vsmith WarrenPlatts Wasell Welsh Whispering Wikinger Wolfkeeper Wtmitchell XJamRastafire Xenonice Yath Zginder Zibem Zocky Zotel 713 anonymousedits
poise (cgs unit) P equiv 10minus1 Pamiddots = 01 Pamiddots
pound per foot hour lb(ftmiddoth) equiv 1 lb(ftmiddoth) asymp 4133 789 times 10minus4 Pamiddots
pound per foot second lb(ftmiddots) equiv 1 lb(ftmiddots) asymp 1488164 Pamiddots
pound-force second per square foot lbfmiddotsft2 equiv 1 lbfmiddotsft2 asymp 4788026 Pamiddots
pound-force second per square inch lbfmiddotsin2 equiv 1 lbfmiddotsin2 asymp 6894757 Pamiddots
Conversion of units 21
Kinematic viscosity
Kinematic viscosity
Name of unit Symbol Definition Relation to SI units
square foot per second ft2s equiv 1 ft2s = 009290304 m2s
square metre per second (SI unit) m2s equiv 1 m2s = 1 m2s
stokes (cgs unit) St equiv10minus4 m2s
= 10minus4 m2s
Electric current
Electric current
Name of unit Symbol Definition Relation to SI units
ampere (SI base unit) A equiv The constant current needed to produce a force of 2 times 10minus7 newton per metre betweentwo straight parallel conductors of infinite length and negligible circular cross-sectionplaced one metre apart in a vacuum[8]
= 1 A
electromagnetic unitabampere (cgs unit)
abamp equiv 10 A = 10 A
esu per secondstatampere (cgs unit)
esus equiv (01 Amiddotms) c asymp3335641 times 10minus10 A
Electric charge
Electric charge
Name of unit Symbol Definition Relation to SI units
abcoulomb electromagnetic unit (cgsunit)
abC emu equiv 10 C = 10 C
atomic unit of charge au equiv e asymp 1602 176462 times 10minus19 C
coulomb (SI unit) C equiv The amount of electricity carried in one second of time by oneampere of current[24]
= 1 C = 1 Amiddots
faraday F equiv 1 mol times NAmiddote asymp 96 4853383 C
statcoulomb franklin electrostatic unit(cgs unit)
statC Fresu
equiv (01 Amiddotm) c asymp 3335 641 times 10minus10 C
Conversion of units 22
Electric dipole
Electric dipole
Name of unit Symbol Definition Relation to SI units
atomic unit of electric dipole moment ea0 asymp 8478 352 81 times 10minus30
Cmiddotm[28]
Electromotive force electric potential difference
Voltage electromotive force
Name ofunit
Symbol Definition Relation to SI units
abvolt (cgsunit)
abV equiv 1 times 10minus8 V = 1 times 10minus8 V
statvolt (cgsunit)
statV equiv cmiddot (1 μJAmiddotm) = 299792 458 V
volt (SIunit)
V The difference in electric potential across two points along a conducting wire carrying one ampereof constant current when the power dissipated between the points equals one watt[24]
= 1 V = 1 WA = 1kgmiddotm2(Amiddots3)
Electrical resistance
Electrical resistance
Name ofunit
Symbol Definition Relation to SI units
ohm (SIunit)
Ω The resistance between two points in a conductor when one volt of electric potential differenceapplied to these points produces one ampere of current in the conductor[24]
= 1 Ω = 1 VA = 1kgmiddotm2(A2middots3)
Capacitance
Capacitors ability to store charge
Name ofunit
Symbol Definition Relation to SI units
farad (SIunit)
F The capacitance between two parallel plates that results in one volt of potential difference whencharged by one coulomb of electricity[24]
= 1 F = 1 CV = 1A2middots4(kgmiddotm2)
Conversion of units 23
Magnetic flux
magnetic flux
Name of unit Symbol Definition Relation to SI units
maxwell (CGSunit)
Mx equiv 10minus8 Wb[29] = 1 times 10minus8 Wb
weber (SIunit)
Wb Magnetic flux which linking a circuit of one turn would produce in it an electromotive force of1 volt if it were reduced to zero at a uniform rate in 1 second[24]
= 1 Wb = 1 Vmiddots = 1kgmiddotm2(Amiddots2)
Magnetic flux density
What physicists call Magnetic field is called Magnetic flux density by electrical engineersand magnetic induction by applied mathematicians and electrical engineers
Name of unit Symbol Definition Relation to SI units
gauss (CGS unit) G equiv Mxcm2 = 10minus4
T= 1 times 10minus4 T [30]
tesla (SI unit) T equiv Wbm2 = 1 T = 1 Wbm2 = 1kg(Amiddots2)
Inductance
Inductance
Name ofunit
Symbol Definition Relation to SI units
henry (SIunit)
H The inductance of a closed circuit that produces one volt of electromotive force when the current inthe circuit varies at a uniform rate of one ampere per second[24]
= 1 H = 1 WbA = 1kgmiddotm2(Amiddots)2
Temperature
Temperature
Name of unit Symbol Definition Conversion to kelvin
degree Celsius degC degC equiv K minus 27315 [K] equiv [degC] + 27315
degree Delisle degDe [K] = 37315 minus [degDe] times 23
degree Fahrenheit degF degF equiv degC times 95 + 32 [K] equiv ([degF] + 45967) times 59
degree Newton degN [K] = [degN] times 10033 + 27315
degree Rankine degR degRa degR equiv K times 95 [K] equiv [degR] times 59
degree Reacuteaumur degReacute [K] = [degReacute] times 54 + 27315
degree Roslashmer degRoslash [K] = ([degRoslash] minus 75) times 4021 + 27315
kelvin (SI baseunit)
K equiv 127316 of the thermodynamic temperature of the triple point of water[8] equiv 1 K
Conversion of units 24
Information entropy
Information entropy
Name of unit Symbol Definition Relation to SI units Relation to bits
SI unit JK equiv JK = 1 JK
nat nip nepit nat equiv kB = 1380 650 5(23) times 10minus23 JK
bit shannon bit b Sh equiv ln(2) times kB = 9569 940 (16) times 10minus24 JK = 1 bit
ban hartley ban Hart equiv ln(10) times kB = 3179 065 3(53) times 10minus23 JK
nibble equiv 4 bits = 3827 976 0(64) times 10minus23 JK = 22 bit
byte B equiv 8 bits = 7655 952 (13) times 10minus23 JK = 23 bit
kilobyte (decimal) kB equiv 1 000 B = 7655 952 (13) times 10minus20 JK
kilobyte (kibibyte) KB KiB equiv 1 024 B = 7839 695 (13) times 10minus20 JK = 210 bit
Often information entropy is measured in shannons whereas the (discrete) storage space of digital devices ismeasured in bits Thus uncompressed redundant data occupy more than one bit of storage per shannon ofinformation entropy The multiples of a bit listed above are usually used with this meaning Other times the bit isused as a measure of information entropy and is thus a synonym of shannon
Luminous intensityThe candela is the preferred nomenclature for the SI unit
Luminous intensity
Name of unit Symbol Definition Relation toSI units
candela (SI baseunit) candle
cd The luminous intensity in a given direction of a source that emits monochromatic radiation offrequency 540 times 1012 hertz and that has a radiant intensity in that direction of 1683 watt persteradian[8]
= 1 cd
candlepower (new) cp equiv cd The use of candlepower as a unit is discouraged due to its ambiguity = 1 cd
candlepower (oldpre-1948)
cp Varies and is poorly reproducible[31] Approximately 0981 cd[14] asymp 0981 cd
Luminance
Conversion of units 25
Luminance
Name of unit Symbol Definition Relation to SI units
candela per square foot cdft2 equiv cdft2 asymp10763910417 cdm2
candela per square inch cdin2 equiv cdin2 asymp 15500031 cdm2
candela per square metre (SI unit) nit (deprecated[14] ) cdm2 equiv cdm2 = 1 cdm2
Name of unit Symbol Definition Relation to SI units
lumen (SIunit)
lm equiv cdmiddotsr = 1 lm = 1 cdmiddotsr
Illuminance
Illuminance
Name of unit Symbol Definition Relation to SI units
footcandle lumen per square foot fc equiv lmft2 = 10763910417 lx
lumen per square inch lmin2 equiv lmin2 asymp 15500031 lx
lux (SI unit) lx equiv lmm2 = 1 lx = 1 lmm2
phot (CGS unit) ph equiv lmcm2 = 1 times 104 lx
Radiation - source activity
Conversion of units 26
Radioactivity
Name of unit Symbol Definition Relation to SI units
becquerel (SIunit)
Bq equiv Number of disintegrations per second = 1 Bq = 1s
curie Ci equiv 37 times 1010 Bq = 37 times 1010 Bq [32]
rutherford (H) rd equiv 1 MBq = 1 times 106 Bq
Please note that although becquerel (Bq) and hertz (Hz) both ultimately refer to the same SI base unit (sminus1) Hz isused only for periodic phenomena and Bq is only used for stochastic processes associated with radioactivity[33]
Radiation - exposure
Radiation - exposure
Name of unit Symbol Definition Relation to SI units
roentgen R 1 R equiv 258 times 10minus4 Ckg[29] = 258 times 10minus4 Ckg
The roentgen is not a SI unit and the NIST strongly discourages its continued use[34]
Radiation - absorbed dose
Radiation - absorbed dose
Name of unit Symbol Definition Relation to SI units
Name of unit Symbol Definition Relation to SI units
Roumlntgen equivalent man rem equiv 001 Sv = 001 Sv
sievert (SI unit) Sv equiv 1 Jkg[33] = 1 Sv
Although the definitions for sievert (Sv) and gray (Gy) would seem to indicate that they measure the same quantitiesthis is not the case The effect of receiving a certain dose of radiation (given as Gy) is variable and depends on manyfactors thus a new unit was needed to denote the biological effectiveness of that dose on the body this is known asthe equivalent dose and is shown in Sv The general relationship between absorbed dose and equivalent dose can berepresented as
H = Q middot D
where H is the equivalent dose D is the absorbed dose and Q is a dimensionless quality factor Thus for anyquantity of D measured in Gy the numerical value for H measured in Sv may be different[36]
Conversion of units 27
Software toolsHome and office computers come with converters in bundled spreadsheet applications or can access free convertersvia the Internet Units and measurements can be easily converted using these tools but only if the units are explicitlydefined and the conversion is compatible (eg cmHg to kPa)
Free conversion softwarebull Units (software) a popular cross-platform command-line utilitybull Converter [37] contextual unit converter for Mozilla Firefox browsersbull Converber [38] portable application converting utilitybull calculla [39] calculla - online web convertersbull iMetrix [40] - unit converter for xpbull uniteasy [41] online scientific unit conversionbull Unit Converter Add-in for Excel [42] - allow a large selection of unit conversions within the Microsoft Excel
spread sheet programbull Unit Converter [43] simple and extensible unit converterbull Portable Unit Converter [44] including 4500 units 33 unit-categories and the possibility to create custom units
General commercial sources of convertersbull Advanced electronic calculators have unit-conversion functionalitybull Spreadsheet programs usually provide conversion functions or formulas or the user can write their ownbull Commercial mathematical scientific and technical applications often include converters
See also
bull Accuracy and precisionbull English unitsbull False precisionbull Imperial unitsbull International System of Unitsbull Mesures usuellesbull Metric system
bull Natural unitsbull Roundingbull Significant figuresbull Temperature conversionbull United States customary unitsbull Units conversion by factor-labelbull Units of measurement
External linksbull British law Units of measurement regulations 1995 [45]
bull ConvertBuster [46] Variety of conversion tools to convert easilybull How Many A dictionary of units of measurement [47]
bull NIST Fundamental physical constants mdash Non-SI units [48]PDF (357 KB)bull NIST Guide to SI Units [49] Many conversion factors listedbull Online Conversion Calculators [50] Very extensive list of conversions from-to equvalent unitsbull The Unified Code for Units of Measure [51]
bull Units Symbols and Conversions XML Dictionary [52]
bull Multilingual Online Conversion of Units [53]
bull Temperature Converter [54]
Conversion of units 28
References[1] United States Naval Observatory (2009) Selected Astronomical Constants 2009 (http asa usno navy mil SecK 2009
Astronomical_Constants_2009 txt) Accessed May 10 2009[2] NIST Reference on Constants Units and Uncertainty (http physics nist gov cgi-bin cuu Valuebohrrada0|search_for=Bohr+
radius)(2006) National Institute of Standards and Technology Retrieved February 22 2008[3] National Institute of Standards and Technology General Tables of Units of Measurement (http ts nist gov WeightsAndMeasures
Publications appxc cfm)[4] Lide D (Ed) (1990) Handbook of Chemistry and Physics (71st ed) Boca Raton FL CRC Press Section 1[5] National Bureau of Standards (June 30 1959) Refinement of values for the yard and the pound Federal Register viewed September 20
2006 at National Geodetic Survey web site (http www ngs noaa gov PUBS_LIB FedRegister FRdoc59-5442 pdf)[6] The International Astronomical Union and Astronomical Units (http www iau org public_press themes measuring )[7] Klein Herbert Arthur (1988) The Science of Measurement a Historical Survey Mineola NY Dover Publications 0-4862-5839-4[8] The International System of Units Section 21 (http www bipm org en si si_brochure chapter2 2-1 ) (8 ed) Bureau International des
Poids et Mesures 2006 retrieved August 26 2009[9] International System of Units (http www bipm org en si si_brochure chapter4 table8 html) 8th ed (2006) Bureau International des
Poids et Mesures Section 41 Table 8[10] P Kenneth Seidelmann Ed (1992) Explanatory Supplement to the Astronomical Almanac Sausalito CA University Science Books p 716
and sv parsec in Glossary[11] Whitelaw Ian (2007) A Measure of All Things The Story of Man and Measurement (http books google com
booksid=3zgGEWM5-iAC) New York Macmillan 0-312-37026-1 p 152[12] De Vinne Theodore Low (1900) The practice of typography a treatise on the processes of type-making the point system the names sizes
styles and prices of plain printing types (http books google com booksid=R4-DjphIpLMC) 2nd ed New York The Century Co p142ndash150
[13] Pasko Wesley Washington (1894) American dictionary of printing and bookmaking (http books google combooksid=Z_QUAAAAIAAJ) (1894) New York Howard Lockwood p 521
[14] Rowlett Russ (2005) How Many A Dictionary of Units of Measurement (http www unc edu ~rowlett units index html)[15] Thompson A and Taylor BN (2008) Guide for the Use of the International System of Units (SI) National Institute of Standards and
Technology Special Publication 811 p 57[16] US Code of Federal Regulations Title 21 Section 1019 Paragraph (b)(5)(viii) (http ecfr gpoaccess gov cgi t text text-idxc=ecframp
rgn=div8amp view=textamp node=212 0 1 1 2 1 1 6amp idno=21) retrieved August 29 2009[17] Barry N Taylor Ed NIST Special Publication 330 The International System of Units (SI) (http physics nist gov Pubs SP330 sp330
pdf) (2001 Edition) Washington US Government Printing Office 43The 12th Conference Generale des Poids et Mesures(CGPM)hellipdeclares that the word ldquolitrerdquo may be employed as a special name for the cubic decimetre
[18] CODATA Value atomic uint of mass (http physics nist gov cgi-bin cuu Valuettme|search_for=atomic+ unit+ of+ mass) (2006)National Institute of Standards and Technology Retrieved 16 September 2008
[19] The Swiss Federal Office for Metrology gives Zentner on a German language web page (http www metas ch de scales systemch html)and quintal on the English translation of that page (http www metas ch en scales systemch html) the unit is marked speacutecifiquementsuisse
[20] Pedersen O (1983) Glossary in Coyne G Hoskin M and Pedersen O Gregorian Reform of the Calendar Proceedings of the VaticanConference to Commemorate its 400th Anniversary Vatican Observatory Available from Astrophysics Data System
[21] Richards EG (1998) Mapping Time Oxford University Press pp 94ndash95 ISBN 0-19-850413-6[22] Steel Duncan (2000) Marking Time John Wiley amp Sons p 46 ISBN 0-471-29827-1[23] CODATA Value atomic unit of force (http physics nist gov cuu Constants ) (2006) National Institute of Standards and Technology
Retrieved September 14 2008[24] [[Comiteacute International des Poids et Mesures (http www bipm org en CIPM db 1946 2 )] Resolution 2] 1946 retrieved August 26
2009[25] Barry N Taylor (April 1995) Guide for the Use of the International System of Units (SI) (http physics nist gov cuu pdf sp811 pdf)
(NIST Special Publication 811) Washington DC US Government Printing Office pp 57ndash68[26] Barry N Taylor (April 1995) Guide for the Use of the International System of Units (SI) (NIST Special Publication 811) Washington DC
US Government Printing Office p 5[27] International System of Units (http www bipm org en si si_brochure chapter4 table7 html) 8th ed (2006) Bureau International des
Poids et Mesures Section 41 Table 7[28] The NIST Reference on Constants Units and Uncertainty (http physics nist gov cgi-bin cuu Valueauedm) 2006 retrieved August
26 2009[29] NIST Guide to SI Units Appendix B9 (http physics nist gov Pubs SP811 appenB9 html) retrieved August 27 2009[30] Standard for the Use of the International System of Units (SI) The Modern Metric System IEEEASTM SI 10-1997 (1997) New York and
West Conshohocken PA Institute of Electrical and Electronics Engineers and American Society for Testing and Materials Tables A1through A5
Conversion of units 29
[31] The NIST Reference on Constants Units and Uncertainty (http physics nist gov cuu Units candela html) retrieved August 28 2009[32] Ambler Thompson amp Barry N Taylor (2008) Guide for the Use of the International System of Units (SI) (http physics nist gov cuu
pdf sp811 pdf) Special Publication 811 Gaithersburg MD National Institute of Standards and Technology p 10[33] The International System of Units Section 222 Table 3 (http www bipm org en si si_brochure chapter2 2-2 table3 html) (8 ed)
Bureau International des Poids et Mesures 2006 retrieved August 27 2009[34] The NIST Guide to the SI (Special Publication 811) section 52 (http physics nist gov Pubs SP811 sec05 html5 2) 2008 retrieved
August 27 2009[35] Ambler Thompson amp Barry N Taylor (2008) Guide for the Use of the International System of Units (SI) (http physics nist gov cuu
pdf sp811 pdf) Special Publication 811 Gaithersburg MD National Institute of Standards and Technology p 5[36] [[Comiteacute international des poids et mesures (http www bipm org en CIPM db 2002 2 )] 2002 Recommendation 2] retrieved
August 27 2009[37] http converter mozdev org[38] http www xyntec com converber htm[39] http www calculla com[40] http illusions hu index phptask=100amp lang=0amp statpage=86[41] http www uniteasy com[42] http www tenderwire com wikipedialandingpage[43] http www kamlex com index phpoption=com_contentamp view=articleamp id=53amp Itemid=55[44] http www sttmedia com unitconverter[45] http www hmso gov uk si si1995 Uksi_19951804_en_2 htm[46] http www convertbuster com[47] http www unc edu ~rowlett units[48] http physics nist gov cuu Document nonsi_in_1998 pdf[49] http physics nist gov Pubs SP811 appenB9 html[50] http www onlineconversion com[51] http aurora rg iupui edu ~schadow units UCUM ucum html[52] http www posc org refs poscUnits20 xml[53] http www imperialtometric com[54] http www tampile com
Article Sources and Contributors 30
Article Sources and ContributorsConversion of units Source httpenwikipediaorgwindexphpoldid=373975089 Contributors 1571781xxx 7 A-giau AVSI Acather96 Ahoerstemeier Alexius08 Altenmann AndreEngels Andrewa Andy120290 Anonymi Ariconte Army1987 ArnoldReinhold Arthur3030 Aspects AxelBoldt AzaToth Azikala BW95 Bdesham Beland Bensaccount Bkumartvm Blackand White BlaiseFEgan BlueEarth Bobblewik Borbrav Bpmullins Bryan Derksen C J B Scholten CORNELIUSSEON CTZMSC3 Calltech Camerajohn Chaosfeary Charles MatthewsChris the speller Cmdrjameson Colonies Chris Conversion script Cope555 Crappy13 Crissov CyrilB DARTH SIDIOUS 2 DMacks DanielCD Dark Formal DarkestSideX DekisugiDenelson83 Dhp1080 Dicklyon DirkvdM Donald Duck Donarreiskoffer Dramatic Dyss DAringsbquougosz Egil Ehrenkater Ejohnsonboulder Elexmax Elf Emokhberi Enon Eob Epbr123Euchiasmus Fathead99 Father Goose Fella22 Femto FernandoAC Fibula Flutefreek Fred Bauder Fredrik Fuhghettaboutit Fuzheado Gaff Gene Nygaard Georgiy1996 Gerry AshtonGiftlite Gilliam Glenn L GoingBatty Goobergunch Gregsexton Greyengine5 Grunt Gurch Gutza HLHJ Haemo Hammersbach Heracles31 Herbee Heron HikerBush Hqb IcairnsIgiffin Indefatigable Isis JBobbitt JHunterJ Jabowery JakeVortex Jamicanmonkey Jason Begin Jay Jc3s5h Jcronen1 Jdoherty Jeffz1 Jeronimo Jimmuhk Jimp Jimwilliams57 JoeinwapJohndburger Josh Parris Jq4bagiq Kaihsu KaneWang Keenan Pepper Kevin Rector KeyStorm Khukri Kurtan Lee Daniel Crocker LightYear Linuxoidoz Liv4christ210 Loggie Lolo252Lupinelawyer M ichaeligl MJCdetroit MTC Mac MacMcF Magore Markus Kuhn Masterqwe MaxHund Maxamegalon2000 Mbeychok Meggar Mh26 Michael Daly Michael Hardy MichelAudy Mikelifeguard Mikhailov Kusserow Mindbuilder Missvain Monger Mr bulow MrOllie MrZhuKeeper Muro de Aguas Mwanner Mwtoews Nandesuka Natkeeran Ndsg NgjaimeNhy67ygv Nick Y Nick123 NickPenguin Ninjagecko Noe Nosilleg Now3r3 Obelix homologator Oldadamml Oleg Alexandrov Olivier Ortolan88 OwenBlacker Pac72 PassargeaPatrick Paul Martin Peter Horn Physchim62 Piels Pierdm Pmanderson Prometheus235 Quadell QuantumEleven Quod erat demonstrandum 314159 Radagast83 Rccoms RedWolfReinyday Revipm Rexparry sydney Reyk Rhetth Rhialto Rich Farmbrough Richard Myers Rjwilmsi Rlsheehan Robin Barry RoySmith Rpwolfgram SD6-Agent SGBailey SamuelLowry Samw Sander123 Seabhcan SebastianHelm Sherbert1 Shinhan Shrew Sietse Snel SimonP Sinbaddasail0r Skotte Smalljim SomeHuman Spencer Srleffler StarwarsmastergeekSteacoon StefanK SteveRamone Stevertigo Stokerm Suisui Sunev Superboy112233 Superm401 Synchronism Tacoman1996 Tarquin Taw Teratornis The Man in Question ThierrycThingg Thinking of England Thunderbird2 Timwi Tobias Hoevekamp Tomasr Tonsofpcs Toon05 Topsykretts2512 Trekphiler Tuwile Twanvl Uday147502 Unitman00 UrhixidurUtherSRG Vargenau Vsmith WarrenPlatts Wasell Welsh Whispering Wikinger Wolfkeeper Wtmitchell XJamRastafire Xenonice Yath Zginder Zibem Zocky Zotel 713 anonymousedits
Name of unit Symbol Definition Relation to SI units
square foot per second ft2s equiv 1 ft2s = 009290304 m2s
square metre per second (SI unit) m2s equiv 1 m2s = 1 m2s
stokes (cgs unit) St equiv10minus4 m2s
= 10minus4 m2s
Electric current
Electric current
Name of unit Symbol Definition Relation to SI units
ampere (SI base unit) A equiv The constant current needed to produce a force of 2 times 10minus7 newton per metre betweentwo straight parallel conductors of infinite length and negligible circular cross-sectionplaced one metre apart in a vacuum[8]
= 1 A
electromagnetic unitabampere (cgs unit)
abamp equiv 10 A = 10 A
esu per secondstatampere (cgs unit)
esus equiv (01 Amiddotms) c asymp3335641 times 10minus10 A
Electric charge
Electric charge
Name of unit Symbol Definition Relation to SI units
abcoulomb electromagnetic unit (cgsunit)
abC emu equiv 10 C = 10 C
atomic unit of charge au equiv e asymp 1602 176462 times 10minus19 C
coulomb (SI unit) C equiv The amount of electricity carried in one second of time by oneampere of current[24]
= 1 C = 1 Amiddots
faraday F equiv 1 mol times NAmiddote asymp 96 4853383 C
statcoulomb franklin electrostatic unit(cgs unit)
statC Fresu
equiv (01 Amiddotm) c asymp 3335 641 times 10minus10 C
Conversion of units 22
Electric dipole
Electric dipole
Name of unit Symbol Definition Relation to SI units
atomic unit of electric dipole moment ea0 asymp 8478 352 81 times 10minus30
Cmiddotm[28]
Electromotive force electric potential difference
Voltage electromotive force
Name ofunit
Symbol Definition Relation to SI units
abvolt (cgsunit)
abV equiv 1 times 10minus8 V = 1 times 10minus8 V
statvolt (cgsunit)
statV equiv cmiddot (1 μJAmiddotm) = 299792 458 V
volt (SIunit)
V The difference in electric potential across two points along a conducting wire carrying one ampereof constant current when the power dissipated between the points equals one watt[24]
= 1 V = 1 WA = 1kgmiddotm2(Amiddots3)
Electrical resistance
Electrical resistance
Name ofunit
Symbol Definition Relation to SI units
ohm (SIunit)
Ω The resistance between two points in a conductor when one volt of electric potential differenceapplied to these points produces one ampere of current in the conductor[24]
= 1 Ω = 1 VA = 1kgmiddotm2(A2middots3)
Capacitance
Capacitors ability to store charge
Name ofunit
Symbol Definition Relation to SI units
farad (SIunit)
F The capacitance between two parallel plates that results in one volt of potential difference whencharged by one coulomb of electricity[24]
= 1 F = 1 CV = 1A2middots4(kgmiddotm2)
Conversion of units 23
Magnetic flux
magnetic flux
Name of unit Symbol Definition Relation to SI units
maxwell (CGSunit)
Mx equiv 10minus8 Wb[29] = 1 times 10minus8 Wb
weber (SIunit)
Wb Magnetic flux which linking a circuit of one turn would produce in it an electromotive force of1 volt if it were reduced to zero at a uniform rate in 1 second[24]
= 1 Wb = 1 Vmiddots = 1kgmiddotm2(Amiddots2)
Magnetic flux density
What physicists call Magnetic field is called Magnetic flux density by electrical engineersand magnetic induction by applied mathematicians and electrical engineers
Name of unit Symbol Definition Relation to SI units
gauss (CGS unit) G equiv Mxcm2 = 10minus4
T= 1 times 10minus4 T [30]
tesla (SI unit) T equiv Wbm2 = 1 T = 1 Wbm2 = 1kg(Amiddots2)
Inductance
Inductance
Name ofunit
Symbol Definition Relation to SI units
henry (SIunit)
H The inductance of a closed circuit that produces one volt of electromotive force when the current inthe circuit varies at a uniform rate of one ampere per second[24]
= 1 H = 1 WbA = 1kgmiddotm2(Amiddots)2
Temperature
Temperature
Name of unit Symbol Definition Conversion to kelvin
degree Celsius degC degC equiv K minus 27315 [K] equiv [degC] + 27315
degree Delisle degDe [K] = 37315 minus [degDe] times 23
degree Fahrenheit degF degF equiv degC times 95 + 32 [K] equiv ([degF] + 45967) times 59
degree Newton degN [K] = [degN] times 10033 + 27315
degree Rankine degR degRa degR equiv K times 95 [K] equiv [degR] times 59
degree Reacuteaumur degReacute [K] = [degReacute] times 54 + 27315
degree Roslashmer degRoslash [K] = ([degRoslash] minus 75) times 4021 + 27315
kelvin (SI baseunit)
K equiv 127316 of the thermodynamic temperature of the triple point of water[8] equiv 1 K
Conversion of units 24
Information entropy
Information entropy
Name of unit Symbol Definition Relation to SI units Relation to bits
SI unit JK equiv JK = 1 JK
nat nip nepit nat equiv kB = 1380 650 5(23) times 10minus23 JK
bit shannon bit b Sh equiv ln(2) times kB = 9569 940 (16) times 10minus24 JK = 1 bit
ban hartley ban Hart equiv ln(10) times kB = 3179 065 3(53) times 10minus23 JK
nibble equiv 4 bits = 3827 976 0(64) times 10minus23 JK = 22 bit
byte B equiv 8 bits = 7655 952 (13) times 10minus23 JK = 23 bit
kilobyte (decimal) kB equiv 1 000 B = 7655 952 (13) times 10minus20 JK
kilobyte (kibibyte) KB KiB equiv 1 024 B = 7839 695 (13) times 10minus20 JK = 210 bit
Often information entropy is measured in shannons whereas the (discrete) storage space of digital devices ismeasured in bits Thus uncompressed redundant data occupy more than one bit of storage per shannon ofinformation entropy The multiples of a bit listed above are usually used with this meaning Other times the bit isused as a measure of information entropy and is thus a synonym of shannon
Luminous intensityThe candela is the preferred nomenclature for the SI unit
Luminous intensity
Name of unit Symbol Definition Relation toSI units
candela (SI baseunit) candle
cd The luminous intensity in a given direction of a source that emits monochromatic radiation offrequency 540 times 1012 hertz and that has a radiant intensity in that direction of 1683 watt persteradian[8]
= 1 cd
candlepower (new) cp equiv cd The use of candlepower as a unit is discouraged due to its ambiguity = 1 cd
candlepower (oldpre-1948)
cp Varies and is poorly reproducible[31] Approximately 0981 cd[14] asymp 0981 cd
Luminance
Conversion of units 25
Luminance
Name of unit Symbol Definition Relation to SI units
candela per square foot cdft2 equiv cdft2 asymp10763910417 cdm2
candela per square inch cdin2 equiv cdin2 asymp 15500031 cdm2
candela per square metre (SI unit) nit (deprecated[14] ) cdm2 equiv cdm2 = 1 cdm2
Name of unit Symbol Definition Relation to SI units
lumen (SIunit)
lm equiv cdmiddotsr = 1 lm = 1 cdmiddotsr
Illuminance
Illuminance
Name of unit Symbol Definition Relation to SI units
footcandle lumen per square foot fc equiv lmft2 = 10763910417 lx
lumen per square inch lmin2 equiv lmin2 asymp 15500031 lx
lux (SI unit) lx equiv lmm2 = 1 lx = 1 lmm2
phot (CGS unit) ph equiv lmcm2 = 1 times 104 lx
Radiation - source activity
Conversion of units 26
Radioactivity
Name of unit Symbol Definition Relation to SI units
becquerel (SIunit)
Bq equiv Number of disintegrations per second = 1 Bq = 1s
curie Ci equiv 37 times 1010 Bq = 37 times 1010 Bq [32]
rutherford (H) rd equiv 1 MBq = 1 times 106 Bq
Please note that although becquerel (Bq) and hertz (Hz) both ultimately refer to the same SI base unit (sminus1) Hz isused only for periodic phenomena and Bq is only used for stochastic processes associated with radioactivity[33]
Radiation - exposure
Radiation - exposure
Name of unit Symbol Definition Relation to SI units
roentgen R 1 R equiv 258 times 10minus4 Ckg[29] = 258 times 10minus4 Ckg
The roentgen is not a SI unit and the NIST strongly discourages its continued use[34]
Radiation - absorbed dose
Radiation - absorbed dose
Name of unit Symbol Definition Relation to SI units
Name of unit Symbol Definition Relation to SI units
Roumlntgen equivalent man rem equiv 001 Sv = 001 Sv
sievert (SI unit) Sv equiv 1 Jkg[33] = 1 Sv
Although the definitions for sievert (Sv) and gray (Gy) would seem to indicate that they measure the same quantitiesthis is not the case The effect of receiving a certain dose of radiation (given as Gy) is variable and depends on manyfactors thus a new unit was needed to denote the biological effectiveness of that dose on the body this is known asthe equivalent dose and is shown in Sv The general relationship between absorbed dose and equivalent dose can berepresented as
H = Q middot D
where H is the equivalent dose D is the absorbed dose and Q is a dimensionless quality factor Thus for anyquantity of D measured in Gy the numerical value for H measured in Sv may be different[36]
Conversion of units 27
Software toolsHome and office computers come with converters in bundled spreadsheet applications or can access free convertersvia the Internet Units and measurements can be easily converted using these tools but only if the units are explicitlydefined and the conversion is compatible (eg cmHg to kPa)
Free conversion softwarebull Units (software) a popular cross-platform command-line utilitybull Converter [37] contextual unit converter for Mozilla Firefox browsersbull Converber [38] portable application converting utilitybull calculla [39] calculla - online web convertersbull iMetrix [40] - unit converter for xpbull uniteasy [41] online scientific unit conversionbull Unit Converter Add-in for Excel [42] - allow a large selection of unit conversions within the Microsoft Excel
spread sheet programbull Unit Converter [43] simple and extensible unit converterbull Portable Unit Converter [44] including 4500 units 33 unit-categories and the possibility to create custom units
General commercial sources of convertersbull Advanced electronic calculators have unit-conversion functionalitybull Spreadsheet programs usually provide conversion functions or formulas or the user can write their ownbull Commercial mathematical scientific and technical applications often include converters
See also
bull Accuracy and precisionbull English unitsbull False precisionbull Imperial unitsbull International System of Unitsbull Mesures usuellesbull Metric system
bull Natural unitsbull Roundingbull Significant figuresbull Temperature conversionbull United States customary unitsbull Units conversion by factor-labelbull Units of measurement
External linksbull British law Units of measurement regulations 1995 [45]
bull ConvertBuster [46] Variety of conversion tools to convert easilybull How Many A dictionary of units of measurement [47]
bull NIST Fundamental physical constants mdash Non-SI units [48]PDF (357 KB)bull NIST Guide to SI Units [49] Many conversion factors listedbull Online Conversion Calculators [50] Very extensive list of conversions from-to equvalent unitsbull The Unified Code for Units of Measure [51]
bull Units Symbols and Conversions XML Dictionary [52]
bull Multilingual Online Conversion of Units [53]
bull Temperature Converter [54]
Conversion of units 28
References[1] United States Naval Observatory (2009) Selected Astronomical Constants 2009 (http asa usno navy mil SecK 2009
Astronomical_Constants_2009 txt) Accessed May 10 2009[2] NIST Reference on Constants Units and Uncertainty (http physics nist gov cgi-bin cuu Valuebohrrada0|search_for=Bohr+
radius)(2006) National Institute of Standards and Technology Retrieved February 22 2008[3] National Institute of Standards and Technology General Tables of Units of Measurement (http ts nist gov WeightsAndMeasures
Publications appxc cfm)[4] Lide D (Ed) (1990) Handbook of Chemistry and Physics (71st ed) Boca Raton FL CRC Press Section 1[5] National Bureau of Standards (June 30 1959) Refinement of values for the yard and the pound Federal Register viewed September 20
2006 at National Geodetic Survey web site (http www ngs noaa gov PUBS_LIB FedRegister FRdoc59-5442 pdf)[6] The International Astronomical Union and Astronomical Units (http www iau org public_press themes measuring )[7] Klein Herbert Arthur (1988) The Science of Measurement a Historical Survey Mineola NY Dover Publications 0-4862-5839-4[8] The International System of Units Section 21 (http www bipm org en si si_brochure chapter2 2-1 ) (8 ed) Bureau International des
Poids et Mesures 2006 retrieved August 26 2009[9] International System of Units (http www bipm org en si si_brochure chapter4 table8 html) 8th ed (2006) Bureau International des
Poids et Mesures Section 41 Table 8[10] P Kenneth Seidelmann Ed (1992) Explanatory Supplement to the Astronomical Almanac Sausalito CA University Science Books p 716
and sv parsec in Glossary[11] Whitelaw Ian (2007) A Measure of All Things The Story of Man and Measurement (http books google com
booksid=3zgGEWM5-iAC) New York Macmillan 0-312-37026-1 p 152[12] De Vinne Theodore Low (1900) The practice of typography a treatise on the processes of type-making the point system the names sizes
styles and prices of plain printing types (http books google com booksid=R4-DjphIpLMC) 2nd ed New York The Century Co p142ndash150
[13] Pasko Wesley Washington (1894) American dictionary of printing and bookmaking (http books google combooksid=Z_QUAAAAIAAJ) (1894) New York Howard Lockwood p 521
[14] Rowlett Russ (2005) How Many A Dictionary of Units of Measurement (http www unc edu ~rowlett units index html)[15] Thompson A and Taylor BN (2008) Guide for the Use of the International System of Units (SI) National Institute of Standards and
Technology Special Publication 811 p 57[16] US Code of Federal Regulations Title 21 Section 1019 Paragraph (b)(5)(viii) (http ecfr gpoaccess gov cgi t text text-idxc=ecframp
rgn=div8amp view=textamp node=212 0 1 1 2 1 1 6amp idno=21) retrieved August 29 2009[17] Barry N Taylor Ed NIST Special Publication 330 The International System of Units (SI) (http physics nist gov Pubs SP330 sp330
pdf) (2001 Edition) Washington US Government Printing Office 43The 12th Conference Generale des Poids et Mesures(CGPM)hellipdeclares that the word ldquolitrerdquo may be employed as a special name for the cubic decimetre
[18] CODATA Value atomic uint of mass (http physics nist gov cgi-bin cuu Valuettme|search_for=atomic+ unit+ of+ mass) (2006)National Institute of Standards and Technology Retrieved 16 September 2008
[19] The Swiss Federal Office for Metrology gives Zentner on a German language web page (http www metas ch de scales systemch html)and quintal on the English translation of that page (http www metas ch en scales systemch html) the unit is marked speacutecifiquementsuisse
[20] Pedersen O (1983) Glossary in Coyne G Hoskin M and Pedersen O Gregorian Reform of the Calendar Proceedings of the VaticanConference to Commemorate its 400th Anniversary Vatican Observatory Available from Astrophysics Data System
[21] Richards EG (1998) Mapping Time Oxford University Press pp 94ndash95 ISBN 0-19-850413-6[22] Steel Duncan (2000) Marking Time John Wiley amp Sons p 46 ISBN 0-471-29827-1[23] CODATA Value atomic unit of force (http physics nist gov cuu Constants ) (2006) National Institute of Standards and Technology
Retrieved September 14 2008[24] [[Comiteacute International des Poids et Mesures (http www bipm org en CIPM db 1946 2 )] Resolution 2] 1946 retrieved August 26
2009[25] Barry N Taylor (April 1995) Guide for the Use of the International System of Units (SI) (http physics nist gov cuu pdf sp811 pdf)
(NIST Special Publication 811) Washington DC US Government Printing Office pp 57ndash68[26] Barry N Taylor (April 1995) Guide for the Use of the International System of Units (SI) (NIST Special Publication 811) Washington DC
US Government Printing Office p 5[27] International System of Units (http www bipm org en si si_brochure chapter4 table7 html) 8th ed (2006) Bureau International des
Poids et Mesures Section 41 Table 7[28] The NIST Reference on Constants Units and Uncertainty (http physics nist gov cgi-bin cuu Valueauedm) 2006 retrieved August
26 2009[29] NIST Guide to SI Units Appendix B9 (http physics nist gov Pubs SP811 appenB9 html) retrieved August 27 2009[30] Standard for the Use of the International System of Units (SI) The Modern Metric System IEEEASTM SI 10-1997 (1997) New York and
West Conshohocken PA Institute of Electrical and Electronics Engineers and American Society for Testing and Materials Tables A1through A5
Conversion of units 29
[31] The NIST Reference on Constants Units and Uncertainty (http physics nist gov cuu Units candela html) retrieved August 28 2009[32] Ambler Thompson amp Barry N Taylor (2008) Guide for the Use of the International System of Units (SI) (http physics nist gov cuu
pdf sp811 pdf) Special Publication 811 Gaithersburg MD National Institute of Standards and Technology p 10[33] The International System of Units Section 222 Table 3 (http www bipm org en si si_brochure chapter2 2-2 table3 html) (8 ed)
Bureau International des Poids et Mesures 2006 retrieved August 27 2009[34] The NIST Guide to the SI (Special Publication 811) section 52 (http physics nist gov Pubs SP811 sec05 html5 2) 2008 retrieved
August 27 2009[35] Ambler Thompson amp Barry N Taylor (2008) Guide for the Use of the International System of Units (SI) (http physics nist gov cuu
pdf sp811 pdf) Special Publication 811 Gaithersburg MD National Institute of Standards and Technology p 5[36] [[Comiteacute international des poids et mesures (http www bipm org en CIPM db 2002 2 )] 2002 Recommendation 2] retrieved
August 27 2009[37] http converter mozdev org[38] http www xyntec com converber htm[39] http www calculla com[40] http illusions hu index phptask=100amp lang=0amp statpage=86[41] http www uniteasy com[42] http www tenderwire com wikipedialandingpage[43] http www kamlex com index phpoption=com_contentamp view=articleamp id=53amp Itemid=55[44] http www sttmedia com unitconverter[45] http www hmso gov uk si si1995 Uksi_19951804_en_2 htm[46] http www convertbuster com[47] http www unc edu ~rowlett units[48] http physics nist gov cuu Document nonsi_in_1998 pdf[49] http physics nist gov Pubs SP811 appenB9 html[50] http www onlineconversion com[51] http aurora rg iupui edu ~schadow units UCUM ucum html[52] http www posc org refs poscUnits20 xml[53] http www imperialtometric com[54] http www tampile com
Article Sources and Contributors 30
Article Sources and ContributorsConversion of units Source httpenwikipediaorgwindexphpoldid=373975089 Contributors 1571781xxx 7 A-giau AVSI Acather96 Ahoerstemeier Alexius08 Altenmann AndreEngels Andrewa Andy120290 Anonymi Ariconte Army1987 ArnoldReinhold Arthur3030 Aspects AxelBoldt AzaToth Azikala BW95 Bdesham Beland Bensaccount Bkumartvm Blackand White BlaiseFEgan BlueEarth Bobblewik Borbrav Bpmullins Bryan Derksen C J B Scholten CORNELIUSSEON CTZMSC3 Calltech Camerajohn Chaosfeary Charles MatthewsChris the speller Cmdrjameson Colonies Chris Conversion script Cope555 Crappy13 Crissov CyrilB DARTH SIDIOUS 2 DMacks DanielCD Dark Formal DarkestSideX DekisugiDenelson83 Dhp1080 Dicklyon DirkvdM Donald Duck Donarreiskoffer Dramatic Dyss DAringsbquougosz Egil Ehrenkater Ejohnsonboulder Elexmax Elf Emokhberi Enon Eob Epbr123Euchiasmus Fathead99 Father Goose Fella22 Femto FernandoAC Fibula Flutefreek Fred Bauder Fredrik Fuhghettaboutit Fuzheado Gaff Gene Nygaard Georgiy1996 Gerry AshtonGiftlite Gilliam Glenn L GoingBatty Goobergunch Gregsexton Greyengine5 Grunt Gurch Gutza HLHJ Haemo Hammersbach Heracles31 Herbee Heron HikerBush Hqb IcairnsIgiffin Indefatigable Isis JBobbitt JHunterJ Jabowery JakeVortex Jamicanmonkey Jason Begin Jay Jc3s5h Jcronen1 Jdoherty Jeffz1 Jeronimo Jimmuhk Jimp Jimwilliams57 JoeinwapJohndburger Josh Parris Jq4bagiq Kaihsu KaneWang Keenan Pepper Kevin Rector KeyStorm Khukri Kurtan Lee Daniel Crocker LightYear Linuxoidoz Liv4christ210 Loggie Lolo252Lupinelawyer M ichaeligl MJCdetroit MTC Mac MacMcF Magore Markus Kuhn Masterqwe MaxHund Maxamegalon2000 Mbeychok Meggar Mh26 Michael Daly Michael Hardy MichelAudy Mikelifeguard Mikhailov Kusserow Mindbuilder Missvain Monger Mr bulow MrOllie MrZhuKeeper Muro de Aguas Mwanner Mwtoews Nandesuka Natkeeran Ndsg NgjaimeNhy67ygv Nick Y Nick123 NickPenguin Ninjagecko Noe Nosilleg Now3r3 Obelix homologator Oldadamml Oleg Alexandrov Olivier Ortolan88 OwenBlacker Pac72 PassargeaPatrick Paul Martin Peter Horn Physchim62 Piels Pierdm Pmanderson Prometheus235 Quadell QuantumEleven Quod erat demonstrandum 314159 Radagast83 Rccoms RedWolfReinyday Revipm Rexparry sydney Reyk Rhetth Rhialto Rich Farmbrough Richard Myers Rjwilmsi Rlsheehan Robin Barry RoySmith Rpwolfgram SD6-Agent SGBailey SamuelLowry Samw Sander123 Seabhcan SebastianHelm Sherbert1 Shinhan Shrew Sietse Snel SimonP Sinbaddasail0r Skotte Smalljim SomeHuman Spencer Srleffler StarwarsmastergeekSteacoon StefanK SteveRamone Stevertigo Stokerm Suisui Sunev Superboy112233 Superm401 Synchronism Tacoman1996 Tarquin Taw Teratornis The Man in Question ThierrycThingg Thinking of England Thunderbird2 Timwi Tobias Hoevekamp Tomasr Tonsofpcs Toon05 Topsykretts2512 Trekphiler Tuwile Twanvl Uday147502 Unitman00 UrhixidurUtherSRG Vargenau Vsmith WarrenPlatts Wasell Welsh Whispering Wikinger Wolfkeeper Wtmitchell XJamRastafire Xenonice Yath Zginder Zibem Zocky Zotel 713 anonymousedits
Name of unit Symbol Definition Relation to SI units
atomic unit of electric dipole moment ea0 asymp 8478 352 81 times 10minus30
Cmiddotm[28]
Electromotive force electric potential difference
Voltage electromotive force
Name ofunit
Symbol Definition Relation to SI units
abvolt (cgsunit)
abV equiv 1 times 10minus8 V = 1 times 10minus8 V
statvolt (cgsunit)
statV equiv cmiddot (1 μJAmiddotm) = 299792 458 V
volt (SIunit)
V The difference in electric potential across two points along a conducting wire carrying one ampereof constant current when the power dissipated between the points equals one watt[24]
= 1 V = 1 WA = 1kgmiddotm2(Amiddots3)
Electrical resistance
Electrical resistance
Name ofunit
Symbol Definition Relation to SI units
ohm (SIunit)
Ω The resistance between two points in a conductor when one volt of electric potential differenceapplied to these points produces one ampere of current in the conductor[24]
= 1 Ω = 1 VA = 1kgmiddotm2(A2middots3)
Capacitance
Capacitors ability to store charge
Name ofunit
Symbol Definition Relation to SI units
farad (SIunit)
F The capacitance between two parallel plates that results in one volt of potential difference whencharged by one coulomb of electricity[24]
= 1 F = 1 CV = 1A2middots4(kgmiddotm2)
Conversion of units 23
Magnetic flux
magnetic flux
Name of unit Symbol Definition Relation to SI units
maxwell (CGSunit)
Mx equiv 10minus8 Wb[29] = 1 times 10minus8 Wb
weber (SIunit)
Wb Magnetic flux which linking a circuit of one turn would produce in it an electromotive force of1 volt if it were reduced to zero at a uniform rate in 1 second[24]
= 1 Wb = 1 Vmiddots = 1kgmiddotm2(Amiddots2)
Magnetic flux density
What physicists call Magnetic field is called Magnetic flux density by electrical engineersand magnetic induction by applied mathematicians and electrical engineers
Name of unit Symbol Definition Relation to SI units
gauss (CGS unit) G equiv Mxcm2 = 10minus4
T= 1 times 10minus4 T [30]
tesla (SI unit) T equiv Wbm2 = 1 T = 1 Wbm2 = 1kg(Amiddots2)
Inductance
Inductance
Name ofunit
Symbol Definition Relation to SI units
henry (SIunit)
H The inductance of a closed circuit that produces one volt of electromotive force when the current inthe circuit varies at a uniform rate of one ampere per second[24]
= 1 H = 1 WbA = 1kgmiddotm2(Amiddots)2
Temperature
Temperature
Name of unit Symbol Definition Conversion to kelvin
degree Celsius degC degC equiv K minus 27315 [K] equiv [degC] + 27315
degree Delisle degDe [K] = 37315 minus [degDe] times 23
degree Fahrenheit degF degF equiv degC times 95 + 32 [K] equiv ([degF] + 45967) times 59
degree Newton degN [K] = [degN] times 10033 + 27315
degree Rankine degR degRa degR equiv K times 95 [K] equiv [degR] times 59
degree Reacuteaumur degReacute [K] = [degReacute] times 54 + 27315
degree Roslashmer degRoslash [K] = ([degRoslash] minus 75) times 4021 + 27315
kelvin (SI baseunit)
K equiv 127316 of the thermodynamic temperature of the triple point of water[8] equiv 1 K
Conversion of units 24
Information entropy
Information entropy
Name of unit Symbol Definition Relation to SI units Relation to bits
SI unit JK equiv JK = 1 JK
nat nip nepit nat equiv kB = 1380 650 5(23) times 10minus23 JK
bit shannon bit b Sh equiv ln(2) times kB = 9569 940 (16) times 10minus24 JK = 1 bit
ban hartley ban Hart equiv ln(10) times kB = 3179 065 3(53) times 10minus23 JK
nibble equiv 4 bits = 3827 976 0(64) times 10minus23 JK = 22 bit
byte B equiv 8 bits = 7655 952 (13) times 10minus23 JK = 23 bit
kilobyte (decimal) kB equiv 1 000 B = 7655 952 (13) times 10minus20 JK
kilobyte (kibibyte) KB KiB equiv 1 024 B = 7839 695 (13) times 10minus20 JK = 210 bit
Often information entropy is measured in shannons whereas the (discrete) storage space of digital devices ismeasured in bits Thus uncompressed redundant data occupy more than one bit of storage per shannon ofinformation entropy The multiples of a bit listed above are usually used with this meaning Other times the bit isused as a measure of information entropy and is thus a synonym of shannon
Luminous intensityThe candela is the preferred nomenclature for the SI unit
Luminous intensity
Name of unit Symbol Definition Relation toSI units
candela (SI baseunit) candle
cd The luminous intensity in a given direction of a source that emits monochromatic radiation offrequency 540 times 1012 hertz and that has a radiant intensity in that direction of 1683 watt persteradian[8]
= 1 cd
candlepower (new) cp equiv cd The use of candlepower as a unit is discouraged due to its ambiguity = 1 cd
candlepower (oldpre-1948)
cp Varies and is poorly reproducible[31] Approximately 0981 cd[14] asymp 0981 cd
Luminance
Conversion of units 25
Luminance
Name of unit Symbol Definition Relation to SI units
candela per square foot cdft2 equiv cdft2 asymp10763910417 cdm2
candela per square inch cdin2 equiv cdin2 asymp 15500031 cdm2
candela per square metre (SI unit) nit (deprecated[14] ) cdm2 equiv cdm2 = 1 cdm2
Name of unit Symbol Definition Relation to SI units
lumen (SIunit)
lm equiv cdmiddotsr = 1 lm = 1 cdmiddotsr
Illuminance
Illuminance
Name of unit Symbol Definition Relation to SI units
footcandle lumen per square foot fc equiv lmft2 = 10763910417 lx
lumen per square inch lmin2 equiv lmin2 asymp 15500031 lx
lux (SI unit) lx equiv lmm2 = 1 lx = 1 lmm2
phot (CGS unit) ph equiv lmcm2 = 1 times 104 lx
Radiation - source activity
Conversion of units 26
Radioactivity
Name of unit Symbol Definition Relation to SI units
becquerel (SIunit)
Bq equiv Number of disintegrations per second = 1 Bq = 1s
curie Ci equiv 37 times 1010 Bq = 37 times 1010 Bq [32]
rutherford (H) rd equiv 1 MBq = 1 times 106 Bq
Please note that although becquerel (Bq) and hertz (Hz) both ultimately refer to the same SI base unit (sminus1) Hz isused only for periodic phenomena and Bq is only used for stochastic processes associated with radioactivity[33]
Radiation - exposure
Radiation - exposure
Name of unit Symbol Definition Relation to SI units
roentgen R 1 R equiv 258 times 10minus4 Ckg[29] = 258 times 10minus4 Ckg
The roentgen is not a SI unit and the NIST strongly discourages its continued use[34]
Radiation - absorbed dose
Radiation - absorbed dose
Name of unit Symbol Definition Relation to SI units
Name of unit Symbol Definition Relation to SI units
Roumlntgen equivalent man rem equiv 001 Sv = 001 Sv
sievert (SI unit) Sv equiv 1 Jkg[33] = 1 Sv
Although the definitions for sievert (Sv) and gray (Gy) would seem to indicate that they measure the same quantitiesthis is not the case The effect of receiving a certain dose of radiation (given as Gy) is variable and depends on manyfactors thus a new unit was needed to denote the biological effectiveness of that dose on the body this is known asthe equivalent dose and is shown in Sv The general relationship between absorbed dose and equivalent dose can berepresented as
H = Q middot D
where H is the equivalent dose D is the absorbed dose and Q is a dimensionless quality factor Thus for anyquantity of D measured in Gy the numerical value for H measured in Sv may be different[36]
Conversion of units 27
Software toolsHome and office computers come with converters in bundled spreadsheet applications or can access free convertersvia the Internet Units and measurements can be easily converted using these tools but only if the units are explicitlydefined and the conversion is compatible (eg cmHg to kPa)
Free conversion softwarebull Units (software) a popular cross-platform command-line utilitybull Converter [37] contextual unit converter for Mozilla Firefox browsersbull Converber [38] portable application converting utilitybull calculla [39] calculla - online web convertersbull iMetrix [40] - unit converter for xpbull uniteasy [41] online scientific unit conversionbull Unit Converter Add-in for Excel [42] - allow a large selection of unit conversions within the Microsoft Excel
spread sheet programbull Unit Converter [43] simple and extensible unit converterbull Portable Unit Converter [44] including 4500 units 33 unit-categories and the possibility to create custom units
General commercial sources of convertersbull Advanced electronic calculators have unit-conversion functionalitybull Spreadsheet programs usually provide conversion functions or formulas or the user can write their ownbull Commercial mathematical scientific and technical applications often include converters
See also
bull Accuracy and precisionbull English unitsbull False precisionbull Imperial unitsbull International System of Unitsbull Mesures usuellesbull Metric system
bull Natural unitsbull Roundingbull Significant figuresbull Temperature conversionbull United States customary unitsbull Units conversion by factor-labelbull Units of measurement
External linksbull British law Units of measurement regulations 1995 [45]
bull ConvertBuster [46] Variety of conversion tools to convert easilybull How Many A dictionary of units of measurement [47]
bull NIST Fundamental physical constants mdash Non-SI units [48]PDF (357 KB)bull NIST Guide to SI Units [49] Many conversion factors listedbull Online Conversion Calculators [50] Very extensive list of conversions from-to equvalent unitsbull The Unified Code for Units of Measure [51]
bull Units Symbols and Conversions XML Dictionary [52]
bull Multilingual Online Conversion of Units [53]
bull Temperature Converter [54]
Conversion of units 28
References[1] United States Naval Observatory (2009) Selected Astronomical Constants 2009 (http asa usno navy mil SecK 2009
Astronomical_Constants_2009 txt) Accessed May 10 2009[2] NIST Reference on Constants Units and Uncertainty (http physics nist gov cgi-bin cuu Valuebohrrada0|search_for=Bohr+
radius)(2006) National Institute of Standards and Technology Retrieved February 22 2008[3] National Institute of Standards and Technology General Tables of Units of Measurement (http ts nist gov WeightsAndMeasures
Publications appxc cfm)[4] Lide D (Ed) (1990) Handbook of Chemistry and Physics (71st ed) Boca Raton FL CRC Press Section 1[5] National Bureau of Standards (June 30 1959) Refinement of values for the yard and the pound Federal Register viewed September 20
2006 at National Geodetic Survey web site (http www ngs noaa gov PUBS_LIB FedRegister FRdoc59-5442 pdf)[6] The International Astronomical Union and Astronomical Units (http www iau org public_press themes measuring )[7] Klein Herbert Arthur (1988) The Science of Measurement a Historical Survey Mineola NY Dover Publications 0-4862-5839-4[8] The International System of Units Section 21 (http www bipm org en si si_brochure chapter2 2-1 ) (8 ed) Bureau International des
Poids et Mesures 2006 retrieved August 26 2009[9] International System of Units (http www bipm org en si si_brochure chapter4 table8 html) 8th ed (2006) Bureau International des
Poids et Mesures Section 41 Table 8[10] P Kenneth Seidelmann Ed (1992) Explanatory Supplement to the Astronomical Almanac Sausalito CA University Science Books p 716
and sv parsec in Glossary[11] Whitelaw Ian (2007) A Measure of All Things The Story of Man and Measurement (http books google com
booksid=3zgGEWM5-iAC) New York Macmillan 0-312-37026-1 p 152[12] De Vinne Theodore Low (1900) The practice of typography a treatise on the processes of type-making the point system the names sizes
styles and prices of plain printing types (http books google com booksid=R4-DjphIpLMC) 2nd ed New York The Century Co p142ndash150
[13] Pasko Wesley Washington (1894) American dictionary of printing and bookmaking (http books google combooksid=Z_QUAAAAIAAJ) (1894) New York Howard Lockwood p 521
[14] Rowlett Russ (2005) How Many A Dictionary of Units of Measurement (http www unc edu ~rowlett units index html)[15] Thompson A and Taylor BN (2008) Guide for the Use of the International System of Units (SI) National Institute of Standards and
Technology Special Publication 811 p 57[16] US Code of Federal Regulations Title 21 Section 1019 Paragraph (b)(5)(viii) (http ecfr gpoaccess gov cgi t text text-idxc=ecframp
rgn=div8amp view=textamp node=212 0 1 1 2 1 1 6amp idno=21) retrieved August 29 2009[17] Barry N Taylor Ed NIST Special Publication 330 The International System of Units (SI) (http physics nist gov Pubs SP330 sp330
pdf) (2001 Edition) Washington US Government Printing Office 43The 12th Conference Generale des Poids et Mesures(CGPM)hellipdeclares that the word ldquolitrerdquo may be employed as a special name for the cubic decimetre
[18] CODATA Value atomic uint of mass (http physics nist gov cgi-bin cuu Valuettme|search_for=atomic+ unit+ of+ mass) (2006)National Institute of Standards and Technology Retrieved 16 September 2008
[19] The Swiss Federal Office for Metrology gives Zentner on a German language web page (http www metas ch de scales systemch html)and quintal on the English translation of that page (http www metas ch en scales systemch html) the unit is marked speacutecifiquementsuisse
[20] Pedersen O (1983) Glossary in Coyne G Hoskin M and Pedersen O Gregorian Reform of the Calendar Proceedings of the VaticanConference to Commemorate its 400th Anniversary Vatican Observatory Available from Astrophysics Data System
[21] Richards EG (1998) Mapping Time Oxford University Press pp 94ndash95 ISBN 0-19-850413-6[22] Steel Duncan (2000) Marking Time John Wiley amp Sons p 46 ISBN 0-471-29827-1[23] CODATA Value atomic unit of force (http physics nist gov cuu Constants ) (2006) National Institute of Standards and Technology
Retrieved September 14 2008[24] [[Comiteacute International des Poids et Mesures (http www bipm org en CIPM db 1946 2 )] Resolution 2] 1946 retrieved August 26
2009[25] Barry N Taylor (April 1995) Guide for the Use of the International System of Units (SI) (http physics nist gov cuu pdf sp811 pdf)
(NIST Special Publication 811) Washington DC US Government Printing Office pp 57ndash68[26] Barry N Taylor (April 1995) Guide for the Use of the International System of Units (SI) (NIST Special Publication 811) Washington DC
US Government Printing Office p 5[27] International System of Units (http www bipm org en si si_brochure chapter4 table7 html) 8th ed (2006) Bureau International des
Poids et Mesures Section 41 Table 7[28] The NIST Reference on Constants Units and Uncertainty (http physics nist gov cgi-bin cuu Valueauedm) 2006 retrieved August
26 2009[29] NIST Guide to SI Units Appendix B9 (http physics nist gov Pubs SP811 appenB9 html) retrieved August 27 2009[30] Standard for the Use of the International System of Units (SI) The Modern Metric System IEEEASTM SI 10-1997 (1997) New York and
West Conshohocken PA Institute of Electrical and Electronics Engineers and American Society for Testing and Materials Tables A1through A5
Conversion of units 29
[31] The NIST Reference on Constants Units and Uncertainty (http physics nist gov cuu Units candela html) retrieved August 28 2009[32] Ambler Thompson amp Barry N Taylor (2008) Guide for the Use of the International System of Units (SI) (http physics nist gov cuu
pdf sp811 pdf) Special Publication 811 Gaithersburg MD National Institute of Standards and Technology p 10[33] The International System of Units Section 222 Table 3 (http www bipm org en si si_brochure chapter2 2-2 table3 html) (8 ed)
Bureau International des Poids et Mesures 2006 retrieved August 27 2009[34] The NIST Guide to the SI (Special Publication 811) section 52 (http physics nist gov Pubs SP811 sec05 html5 2) 2008 retrieved
August 27 2009[35] Ambler Thompson amp Barry N Taylor (2008) Guide for the Use of the International System of Units (SI) (http physics nist gov cuu
pdf sp811 pdf) Special Publication 811 Gaithersburg MD National Institute of Standards and Technology p 5[36] [[Comiteacute international des poids et mesures (http www bipm org en CIPM db 2002 2 )] 2002 Recommendation 2] retrieved
August 27 2009[37] http converter mozdev org[38] http www xyntec com converber htm[39] http www calculla com[40] http illusions hu index phptask=100amp lang=0amp statpage=86[41] http www uniteasy com[42] http www tenderwire com wikipedialandingpage[43] http www kamlex com index phpoption=com_contentamp view=articleamp id=53amp Itemid=55[44] http www sttmedia com unitconverter[45] http www hmso gov uk si si1995 Uksi_19951804_en_2 htm[46] http www convertbuster com[47] http www unc edu ~rowlett units[48] http physics nist gov cuu Document nonsi_in_1998 pdf[49] http physics nist gov Pubs SP811 appenB9 html[50] http www onlineconversion com[51] http aurora rg iupui edu ~schadow units UCUM ucum html[52] http www posc org refs poscUnits20 xml[53] http www imperialtometric com[54] http www tampile com
Article Sources and Contributors 30
Article Sources and ContributorsConversion of units Source httpenwikipediaorgwindexphpoldid=373975089 Contributors 1571781xxx 7 A-giau AVSI Acather96 Ahoerstemeier Alexius08 Altenmann AndreEngels Andrewa Andy120290 Anonymi Ariconte Army1987 ArnoldReinhold Arthur3030 Aspects AxelBoldt AzaToth Azikala BW95 Bdesham Beland Bensaccount Bkumartvm Blackand White BlaiseFEgan BlueEarth Bobblewik Borbrav Bpmullins Bryan Derksen C J B Scholten CORNELIUSSEON CTZMSC3 Calltech Camerajohn Chaosfeary Charles MatthewsChris the speller Cmdrjameson Colonies Chris Conversion script Cope555 Crappy13 Crissov CyrilB DARTH SIDIOUS 2 DMacks DanielCD Dark Formal DarkestSideX DekisugiDenelson83 Dhp1080 Dicklyon DirkvdM Donald Duck Donarreiskoffer Dramatic Dyss DAringsbquougosz Egil Ehrenkater Ejohnsonboulder Elexmax Elf Emokhberi Enon Eob Epbr123Euchiasmus Fathead99 Father Goose Fella22 Femto FernandoAC Fibula Flutefreek Fred Bauder Fredrik Fuhghettaboutit Fuzheado Gaff Gene Nygaard Georgiy1996 Gerry AshtonGiftlite Gilliam Glenn L GoingBatty Goobergunch Gregsexton Greyengine5 Grunt Gurch Gutza HLHJ Haemo Hammersbach Heracles31 Herbee Heron HikerBush Hqb IcairnsIgiffin Indefatigable Isis JBobbitt JHunterJ Jabowery JakeVortex Jamicanmonkey Jason Begin Jay Jc3s5h Jcronen1 Jdoherty Jeffz1 Jeronimo Jimmuhk Jimp Jimwilliams57 JoeinwapJohndburger Josh Parris Jq4bagiq Kaihsu KaneWang Keenan Pepper Kevin Rector KeyStorm Khukri Kurtan Lee Daniel Crocker LightYear Linuxoidoz Liv4christ210 Loggie Lolo252Lupinelawyer M ichaeligl MJCdetroit MTC Mac MacMcF Magore Markus Kuhn Masterqwe MaxHund Maxamegalon2000 Mbeychok Meggar Mh26 Michael Daly Michael Hardy MichelAudy Mikelifeguard Mikhailov Kusserow Mindbuilder Missvain Monger Mr bulow MrOllie MrZhuKeeper Muro de Aguas Mwanner Mwtoews Nandesuka Natkeeran Ndsg NgjaimeNhy67ygv Nick Y Nick123 NickPenguin Ninjagecko Noe Nosilleg Now3r3 Obelix homologator Oldadamml Oleg Alexandrov Olivier Ortolan88 OwenBlacker Pac72 PassargeaPatrick Paul Martin Peter Horn Physchim62 Piels Pierdm Pmanderson Prometheus235 Quadell QuantumEleven Quod erat demonstrandum 314159 Radagast83 Rccoms RedWolfReinyday Revipm Rexparry sydney Reyk Rhetth Rhialto Rich Farmbrough Richard Myers Rjwilmsi Rlsheehan Robin Barry RoySmith Rpwolfgram SD6-Agent SGBailey SamuelLowry Samw Sander123 Seabhcan SebastianHelm Sherbert1 Shinhan Shrew Sietse Snel SimonP Sinbaddasail0r Skotte Smalljim SomeHuman Spencer Srleffler StarwarsmastergeekSteacoon StefanK SteveRamone Stevertigo Stokerm Suisui Sunev Superboy112233 Superm401 Synchronism Tacoman1996 Tarquin Taw Teratornis The Man in Question ThierrycThingg Thinking of England Thunderbird2 Timwi Tobias Hoevekamp Tomasr Tonsofpcs Toon05 Topsykretts2512 Trekphiler Tuwile Twanvl Uday147502 Unitman00 UrhixidurUtherSRG Vargenau Vsmith WarrenPlatts Wasell Welsh Whispering Wikinger Wolfkeeper Wtmitchell XJamRastafire Xenonice Yath Zginder Zibem Zocky Zotel 713 anonymousedits
Name of unit Symbol Definition Relation to SI units
maxwell (CGSunit)
Mx equiv 10minus8 Wb[29] = 1 times 10minus8 Wb
weber (SIunit)
Wb Magnetic flux which linking a circuit of one turn would produce in it an electromotive force of1 volt if it were reduced to zero at a uniform rate in 1 second[24]
= 1 Wb = 1 Vmiddots = 1kgmiddotm2(Amiddots2)
Magnetic flux density
What physicists call Magnetic field is called Magnetic flux density by electrical engineersand magnetic induction by applied mathematicians and electrical engineers
Name of unit Symbol Definition Relation to SI units
gauss (CGS unit) G equiv Mxcm2 = 10minus4
T= 1 times 10minus4 T [30]
tesla (SI unit) T equiv Wbm2 = 1 T = 1 Wbm2 = 1kg(Amiddots2)
Inductance
Inductance
Name ofunit
Symbol Definition Relation to SI units
henry (SIunit)
H The inductance of a closed circuit that produces one volt of electromotive force when the current inthe circuit varies at a uniform rate of one ampere per second[24]
= 1 H = 1 WbA = 1kgmiddotm2(Amiddots)2
Temperature
Temperature
Name of unit Symbol Definition Conversion to kelvin
degree Celsius degC degC equiv K minus 27315 [K] equiv [degC] + 27315
degree Delisle degDe [K] = 37315 minus [degDe] times 23
degree Fahrenheit degF degF equiv degC times 95 + 32 [K] equiv ([degF] + 45967) times 59
degree Newton degN [K] = [degN] times 10033 + 27315
degree Rankine degR degRa degR equiv K times 95 [K] equiv [degR] times 59
degree Reacuteaumur degReacute [K] = [degReacute] times 54 + 27315
degree Roslashmer degRoslash [K] = ([degRoslash] minus 75) times 4021 + 27315
kelvin (SI baseunit)
K equiv 127316 of the thermodynamic temperature of the triple point of water[8] equiv 1 K
Conversion of units 24
Information entropy
Information entropy
Name of unit Symbol Definition Relation to SI units Relation to bits
SI unit JK equiv JK = 1 JK
nat nip nepit nat equiv kB = 1380 650 5(23) times 10minus23 JK
bit shannon bit b Sh equiv ln(2) times kB = 9569 940 (16) times 10minus24 JK = 1 bit
ban hartley ban Hart equiv ln(10) times kB = 3179 065 3(53) times 10minus23 JK
nibble equiv 4 bits = 3827 976 0(64) times 10minus23 JK = 22 bit
byte B equiv 8 bits = 7655 952 (13) times 10minus23 JK = 23 bit
kilobyte (decimal) kB equiv 1 000 B = 7655 952 (13) times 10minus20 JK
kilobyte (kibibyte) KB KiB equiv 1 024 B = 7839 695 (13) times 10minus20 JK = 210 bit
Often information entropy is measured in shannons whereas the (discrete) storage space of digital devices ismeasured in bits Thus uncompressed redundant data occupy more than one bit of storage per shannon ofinformation entropy The multiples of a bit listed above are usually used with this meaning Other times the bit isused as a measure of information entropy and is thus a synonym of shannon
Luminous intensityThe candela is the preferred nomenclature for the SI unit
Luminous intensity
Name of unit Symbol Definition Relation toSI units
candela (SI baseunit) candle
cd The luminous intensity in a given direction of a source that emits monochromatic radiation offrequency 540 times 1012 hertz and that has a radiant intensity in that direction of 1683 watt persteradian[8]
= 1 cd
candlepower (new) cp equiv cd The use of candlepower as a unit is discouraged due to its ambiguity = 1 cd
candlepower (oldpre-1948)
cp Varies and is poorly reproducible[31] Approximately 0981 cd[14] asymp 0981 cd
Luminance
Conversion of units 25
Luminance
Name of unit Symbol Definition Relation to SI units
candela per square foot cdft2 equiv cdft2 asymp10763910417 cdm2
candela per square inch cdin2 equiv cdin2 asymp 15500031 cdm2
candela per square metre (SI unit) nit (deprecated[14] ) cdm2 equiv cdm2 = 1 cdm2
Name of unit Symbol Definition Relation to SI units
lumen (SIunit)
lm equiv cdmiddotsr = 1 lm = 1 cdmiddotsr
Illuminance
Illuminance
Name of unit Symbol Definition Relation to SI units
footcandle lumen per square foot fc equiv lmft2 = 10763910417 lx
lumen per square inch lmin2 equiv lmin2 asymp 15500031 lx
lux (SI unit) lx equiv lmm2 = 1 lx = 1 lmm2
phot (CGS unit) ph equiv lmcm2 = 1 times 104 lx
Radiation - source activity
Conversion of units 26
Radioactivity
Name of unit Symbol Definition Relation to SI units
becquerel (SIunit)
Bq equiv Number of disintegrations per second = 1 Bq = 1s
curie Ci equiv 37 times 1010 Bq = 37 times 1010 Bq [32]
rutherford (H) rd equiv 1 MBq = 1 times 106 Bq
Please note that although becquerel (Bq) and hertz (Hz) both ultimately refer to the same SI base unit (sminus1) Hz isused only for periodic phenomena and Bq is only used for stochastic processes associated with radioactivity[33]
Radiation - exposure
Radiation - exposure
Name of unit Symbol Definition Relation to SI units
roentgen R 1 R equiv 258 times 10minus4 Ckg[29] = 258 times 10minus4 Ckg
The roentgen is not a SI unit and the NIST strongly discourages its continued use[34]
Radiation - absorbed dose
Radiation - absorbed dose
Name of unit Symbol Definition Relation to SI units
Name of unit Symbol Definition Relation to SI units
Roumlntgen equivalent man rem equiv 001 Sv = 001 Sv
sievert (SI unit) Sv equiv 1 Jkg[33] = 1 Sv
Although the definitions for sievert (Sv) and gray (Gy) would seem to indicate that they measure the same quantitiesthis is not the case The effect of receiving a certain dose of radiation (given as Gy) is variable and depends on manyfactors thus a new unit was needed to denote the biological effectiveness of that dose on the body this is known asthe equivalent dose and is shown in Sv The general relationship between absorbed dose and equivalent dose can berepresented as
H = Q middot D
where H is the equivalent dose D is the absorbed dose and Q is a dimensionless quality factor Thus for anyquantity of D measured in Gy the numerical value for H measured in Sv may be different[36]
Conversion of units 27
Software toolsHome and office computers come with converters in bundled spreadsheet applications or can access free convertersvia the Internet Units and measurements can be easily converted using these tools but only if the units are explicitlydefined and the conversion is compatible (eg cmHg to kPa)
Free conversion softwarebull Units (software) a popular cross-platform command-line utilitybull Converter [37] contextual unit converter for Mozilla Firefox browsersbull Converber [38] portable application converting utilitybull calculla [39] calculla - online web convertersbull iMetrix [40] - unit converter for xpbull uniteasy [41] online scientific unit conversionbull Unit Converter Add-in for Excel [42] - allow a large selection of unit conversions within the Microsoft Excel
spread sheet programbull Unit Converter [43] simple and extensible unit converterbull Portable Unit Converter [44] including 4500 units 33 unit-categories and the possibility to create custom units
General commercial sources of convertersbull Advanced electronic calculators have unit-conversion functionalitybull Spreadsheet programs usually provide conversion functions or formulas or the user can write their ownbull Commercial mathematical scientific and technical applications often include converters
See also
bull Accuracy and precisionbull English unitsbull False precisionbull Imperial unitsbull International System of Unitsbull Mesures usuellesbull Metric system
bull Natural unitsbull Roundingbull Significant figuresbull Temperature conversionbull United States customary unitsbull Units conversion by factor-labelbull Units of measurement
External linksbull British law Units of measurement regulations 1995 [45]
bull ConvertBuster [46] Variety of conversion tools to convert easilybull How Many A dictionary of units of measurement [47]
bull NIST Fundamental physical constants mdash Non-SI units [48]PDF (357 KB)bull NIST Guide to SI Units [49] Many conversion factors listedbull Online Conversion Calculators [50] Very extensive list of conversions from-to equvalent unitsbull The Unified Code for Units of Measure [51]
bull Units Symbols and Conversions XML Dictionary [52]
bull Multilingual Online Conversion of Units [53]
bull Temperature Converter [54]
Conversion of units 28
References[1] United States Naval Observatory (2009) Selected Astronomical Constants 2009 (http asa usno navy mil SecK 2009
Astronomical_Constants_2009 txt) Accessed May 10 2009[2] NIST Reference on Constants Units and Uncertainty (http physics nist gov cgi-bin cuu Valuebohrrada0|search_for=Bohr+
radius)(2006) National Institute of Standards and Technology Retrieved February 22 2008[3] National Institute of Standards and Technology General Tables of Units of Measurement (http ts nist gov WeightsAndMeasures
Publications appxc cfm)[4] Lide D (Ed) (1990) Handbook of Chemistry and Physics (71st ed) Boca Raton FL CRC Press Section 1[5] National Bureau of Standards (June 30 1959) Refinement of values for the yard and the pound Federal Register viewed September 20
2006 at National Geodetic Survey web site (http www ngs noaa gov PUBS_LIB FedRegister FRdoc59-5442 pdf)[6] The International Astronomical Union and Astronomical Units (http www iau org public_press themes measuring )[7] Klein Herbert Arthur (1988) The Science of Measurement a Historical Survey Mineola NY Dover Publications 0-4862-5839-4[8] The International System of Units Section 21 (http www bipm org en si si_brochure chapter2 2-1 ) (8 ed) Bureau International des
Poids et Mesures 2006 retrieved August 26 2009[9] International System of Units (http www bipm org en si si_brochure chapter4 table8 html) 8th ed (2006) Bureau International des
Poids et Mesures Section 41 Table 8[10] P Kenneth Seidelmann Ed (1992) Explanatory Supplement to the Astronomical Almanac Sausalito CA University Science Books p 716
and sv parsec in Glossary[11] Whitelaw Ian (2007) A Measure of All Things The Story of Man and Measurement (http books google com
booksid=3zgGEWM5-iAC) New York Macmillan 0-312-37026-1 p 152[12] De Vinne Theodore Low (1900) The practice of typography a treatise on the processes of type-making the point system the names sizes
styles and prices of plain printing types (http books google com booksid=R4-DjphIpLMC) 2nd ed New York The Century Co p142ndash150
[13] Pasko Wesley Washington (1894) American dictionary of printing and bookmaking (http books google combooksid=Z_QUAAAAIAAJ) (1894) New York Howard Lockwood p 521
[14] Rowlett Russ (2005) How Many A Dictionary of Units of Measurement (http www unc edu ~rowlett units index html)[15] Thompson A and Taylor BN (2008) Guide for the Use of the International System of Units (SI) National Institute of Standards and
Technology Special Publication 811 p 57[16] US Code of Federal Regulations Title 21 Section 1019 Paragraph (b)(5)(viii) (http ecfr gpoaccess gov cgi t text text-idxc=ecframp
rgn=div8amp view=textamp node=212 0 1 1 2 1 1 6amp idno=21) retrieved August 29 2009[17] Barry N Taylor Ed NIST Special Publication 330 The International System of Units (SI) (http physics nist gov Pubs SP330 sp330
pdf) (2001 Edition) Washington US Government Printing Office 43The 12th Conference Generale des Poids et Mesures(CGPM)hellipdeclares that the word ldquolitrerdquo may be employed as a special name for the cubic decimetre
[18] CODATA Value atomic uint of mass (http physics nist gov cgi-bin cuu Valuettme|search_for=atomic+ unit+ of+ mass) (2006)National Institute of Standards and Technology Retrieved 16 September 2008
[19] The Swiss Federal Office for Metrology gives Zentner on a German language web page (http www metas ch de scales systemch html)and quintal on the English translation of that page (http www metas ch en scales systemch html) the unit is marked speacutecifiquementsuisse
[20] Pedersen O (1983) Glossary in Coyne G Hoskin M and Pedersen O Gregorian Reform of the Calendar Proceedings of the VaticanConference to Commemorate its 400th Anniversary Vatican Observatory Available from Astrophysics Data System
[21] Richards EG (1998) Mapping Time Oxford University Press pp 94ndash95 ISBN 0-19-850413-6[22] Steel Duncan (2000) Marking Time John Wiley amp Sons p 46 ISBN 0-471-29827-1[23] CODATA Value atomic unit of force (http physics nist gov cuu Constants ) (2006) National Institute of Standards and Technology
Retrieved September 14 2008[24] [[Comiteacute International des Poids et Mesures (http www bipm org en CIPM db 1946 2 )] Resolution 2] 1946 retrieved August 26
2009[25] Barry N Taylor (April 1995) Guide for the Use of the International System of Units (SI) (http physics nist gov cuu pdf sp811 pdf)
(NIST Special Publication 811) Washington DC US Government Printing Office pp 57ndash68[26] Barry N Taylor (April 1995) Guide for the Use of the International System of Units (SI) (NIST Special Publication 811) Washington DC
US Government Printing Office p 5[27] International System of Units (http www bipm org en si si_brochure chapter4 table7 html) 8th ed (2006) Bureau International des
Poids et Mesures Section 41 Table 7[28] The NIST Reference on Constants Units and Uncertainty (http physics nist gov cgi-bin cuu Valueauedm) 2006 retrieved August
26 2009[29] NIST Guide to SI Units Appendix B9 (http physics nist gov Pubs SP811 appenB9 html) retrieved August 27 2009[30] Standard for the Use of the International System of Units (SI) The Modern Metric System IEEEASTM SI 10-1997 (1997) New York and
West Conshohocken PA Institute of Electrical and Electronics Engineers and American Society for Testing and Materials Tables A1through A5
Conversion of units 29
[31] The NIST Reference on Constants Units and Uncertainty (http physics nist gov cuu Units candela html) retrieved August 28 2009[32] Ambler Thompson amp Barry N Taylor (2008) Guide for the Use of the International System of Units (SI) (http physics nist gov cuu
pdf sp811 pdf) Special Publication 811 Gaithersburg MD National Institute of Standards and Technology p 10[33] The International System of Units Section 222 Table 3 (http www bipm org en si si_brochure chapter2 2-2 table3 html) (8 ed)
Bureau International des Poids et Mesures 2006 retrieved August 27 2009[34] The NIST Guide to the SI (Special Publication 811) section 52 (http physics nist gov Pubs SP811 sec05 html5 2) 2008 retrieved
August 27 2009[35] Ambler Thompson amp Barry N Taylor (2008) Guide for the Use of the International System of Units (SI) (http physics nist gov cuu
pdf sp811 pdf) Special Publication 811 Gaithersburg MD National Institute of Standards and Technology p 5[36] [[Comiteacute international des poids et mesures (http www bipm org en CIPM db 2002 2 )] 2002 Recommendation 2] retrieved
August 27 2009[37] http converter mozdev org[38] http www xyntec com converber htm[39] http www calculla com[40] http illusions hu index phptask=100amp lang=0amp statpage=86[41] http www uniteasy com[42] http www tenderwire com wikipedialandingpage[43] http www kamlex com index phpoption=com_contentamp view=articleamp id=53amp Itemid=55[44] http www sttmedia com unitconverter[45] http www hmso gov uk si si1995 Uksi_19951804_en_2 htm[46] http www convertbuster com[47] http www unc edu ~rowlett units[48] http physics nist gov cuu Document nonsi_in_1998 pdf[49] http physics nist gov Pubs SP811 appenB9 html[50] http www onlineconversion com[51] http aurora rg iupui edu ~schadow units UCUM ucum html[52] http www posc org refs poscUnits20 xml[53] http www imperialtometric com[54] http www tampile com
Article Sources and Contributors 30
Article Sources and ContributorsConversion of units Source httpenwikipediaorgwindexphpoldid=373975089 Contributors 1571781xxx 7 A-giau AVSI Acather96 Ahoerstemeier Alexius08 Altenmann AndreEngels Andrewa Andy120290 Anonymi Ariconte Army1987 ArnoldReinhold Arthur3030 Aspects AxelBoldt AzaToth Azikala BW95 Bdesham Beland Bensaccount Bkumartvm Blackand White BlaiseFEgan BlueEarth Bobblewik Borbrav Bpmullins Bryan Derksen C J B Scholten CORNELIUSSEON CTZMSC3 Calltech Camerajohn Chaosfeary Charles MatthewsChris the speller Cmdrjameson Colonies Chris Conversion script Cope555 Crappy13 Crissov CyrilB DARTH SIDIOUS 2 DMacks DanielCD Dark Formal DarkestSideX DekisugiDenelson83 Dhp1080 Dicklyon DirkvdM Donald Duck Donarreiskoffer Dramatic Dyss DAringsbquougosz Egil Ehrenkater Ejohnsonboulder Elexmax Elf Emokhberi Enon Eob Epbr123Euchiasmus Fathead99 Father Goose Fella22 Femto FernandoAC Fibula Flutefreek Fred Bauder Fredrik Fuhghettaboutit Fuzheado Gaff Gene Nygaard Georgiy1996 Gerry AshtonGiftlite Gilliam Glenn L GoingBatty Goobergunch Gregsexton Greyengine5 Grunt Gurch Gutza HLHJ Haemo Hammersbach Heracles31 Herbee Heron HikerBush Hqb IcairnsIgiffin Indefatigable Isis JBobbitt JHunterJ Jabowery JakeVortex Jamicanmonkey Jason Begin Jay Jc3s5h Jcronen1 Jdoherty Jeffz1 Jeronimo Jimmuhk Jimp Jimwilliams57 JoeinwapJohndburger Josh Parris Jq4bagiq Kaihsu KaneWang Keenan Pepper Kevin Rector KeyStorm Khukri Kurtan Lee Daniel Crocker LightYear Linuxoidoz Liv4christ210 Loggie Lolo252Lupinelawyer M ichaeligl MJCdetroit MTC Mac MacMcF Magore Markus Kuhn Masterqwe MaxHund Maxamegalon2000 Mbeychok Meggar Mh26 Michael Daly Michael Hardy MichelAudy Mikelifeguard Mikhailov Kusserow Mindbuilder Missvain Monger Mr bulow MrOllie MrZhuKeeper Muro de Aguas Mwanner Mwtoews Nandesuka Natkeeran Ndsg NgjaimeNhy67ygv Nick Y Nick123 NickPenguin Ninjagecko Noe Nosilleg Now3r3 Obelix homologator Oldadamml Oleg Alexandrov Olivier Ortolan88 OwenBlacker Pac72 PassargeaPatrick Paul Martin Peter Horn Physchim62 Piels Pierdm Pmanderson Prometheus235 Quadell QuantumEleven Quod erat demonstrandum 314159 Radagast83 Rccoms RedWolfReinyday Revipm Rexparry sydney Reyk Rhetth Rhialto Rich Farmbrough Richard Myers Rjwilmsi Rlsheehan Robin Barry RoySmith Rpwolfgram SD6-Agent SGBailey SamuelLowry Samw Sander123 Seabhcan SebastianHelm Sherbert1 Shinhan Shrew Sietse Snel SimonP Sinbaddasail0r Skotte Smalljim SomeHuman Spencer Srleffler StarwarsmastergeekSteacoon StefanK SteveRamone Stevertigo Stokerm Suisui Sunev Superboy112233 Superm401 Synchronism Tacoman1996 Tarquin Taw Teratornis The Man in Question ThierrycThingg Thinking of England Thunderbird2 Timwi Tobias Hoevekamp Tomasr Tonsofpcs Toon05 Topsykretts2512 Trekphiler Tuwile Twanvl Uday147502 Unitman00 UrhixidurUtherSRG Vargenau Vsmith WarrenPlatts Wasell Welsh Whispering Wikinger Wolfkeeper Wtmitchell XJamRastafire Xenonice Yath Zginder Zibem Zocky Zotel 713 anonymousedits
Name of unit Symbol Definition Relation to SI units Relation to bits
SI unit JK equiv JK = 1 JK
nat nip nepit nat equiv kB = 1380 650 5(23) times 10minus23 JK
bit shannon bit b Sh equiv ln(2) times kB = 9569 940 (16) times 10minus24 JK = 1 bit
ban hartley ban Hart equiv ln(10) times kB = 3179 065 3(53) times 10minus23 JK
nibble equiv 4 bits = 3827 976 0(64) times 10minus23 JK = 22 bit
byte B equiv 8 bits = 7655 952 (13) times 10minus23 JK = 23 bit
kilobyte (decimal) kB equiv 1 000 B = 7655 952 (13) times 10minus20 JK
kilobyte (kibibyte) KB KiB equiv 1 024 B = 7839 695 (13) times 10minus20 JK = 210 bit
Often information entropy is measured in shannons whereas the (discrete) storage space of digital devices ismeasured in bits Thus uncompressed redundant data occupy more than one bit of storage per shannon ofinformation entropy The multiples of a bit listed above are usually used with this meaning Other times the bit isused as a measure of information entropy and is thus a synonym of shannon
Luminous intensityThe candela is the preferred nomenclature for the SI unit
Luminous intensity
Name of unit Symbol Definition Relation toSI units
candela (SI baseunit) candle
cd The luminous intensity in a given direction of a source that emits monochromatic radiation offrequency 540 times 1012 hertz and that has a radiant intensity in that direction of 1683 watt persteradian[8]
= 1 cd
candlepower (new) cp equiv cd The use of candlepower as a unit is discouraged due to its ambiguity = 1 cd
candlepower (oldpre-1948)
cp Varies and is poorly reproducible[31] Approximately 0981 cd[14] asymp 0981 cd
Luminance
Conversion of units 25
Luminance
Name of unit Symbol Definition Relation to SI units
candela per square foot cdft2 equiv cdft2 asymp10763910417 cdm2
candela per square inch cdin2 equiv cdin2 asymp 15500031 cdm2
candela per square metre (SI unit) nit (deprecated[14] ) cdm2 equiv cdm2 = 1 cdm2
Name of unit Symbol Definition Relation to SI units
lumen (SIunit)
lm equiv cdmiddotsr = 1 lm = 1 cdmiddotsr
Illuminance
Illuminance
Name of unit Symbol Definition Relation to SI units
footcandle lumen per square foot fc equiv lmft2 = 10763910417 lx
lumen per square inch lmin2 equiv lmin2 asymp 15500031 lx
lux (SI unit) lx equiv lmm2 = 1 lx = 1 lmm2
phot (CGS unit) ph equiv lmcm2 = 1 times 104 lx
Radiation - source activity
Conversion of units 26
Radioactivity
Name of unit Symbol Definition Relation to SI units
becquerel (SIunit)
Bq equiv Number of disintegrations per second = 1 Bq = 1s
curie Ci equiv 37 times 1010 Bq = 37 times 1010 Bq [32]
rutherford (H) rd equiv 1 MBq = 1 times 106 Bq
Please note that although becquerel (Bq) and hertz (Hz) both ultimately refer to the same SI base unit (sminus1) Hz isused only for periodic phenomena and Bq is only used for stochastic processes associated with radioactivity[33]
Radiation - exposure
Radiation - exposure
Name of unit Symbol Definition Relation to SI units
roentgen R 1 R equiv 258 times 10minus4 Ckg[29] = 258 times 10minus4 Ckg
The roentgen is not a SI unit and the NIST strongly discourages its continued use[34]
Radiation - absorbed dose
Radiation - absorbed dose
Name of unit Symbol Definition Relation to SI units
Name of unit Symbol Definition Relation to SI units
Roumlntgen equivalent man rem equiv 001 Sv = 001 Sv
sievert (SI unit) Sv equiv 1 Jkg[33] = 1 Sv
Although the definitions for sievert (Sv) and gray (Gy) would seem to indicate that they measure the same quantitiesthis is not the case The effect of receiving a certain dose of radiation (given as Gy) is variable and depends on manyfactors thus a new unit was needed to denote the biological effectiveness of that dose on the body this is known asthe equivalent dose and is shown in Sv The general relationship between absorbed dose and equivalent dose can berepresented as
H = Q middot D
where H is the equivalent dose D is the absorbed dose and Q is a dimensionless quality factor Thus for anyquantity of D measured in Gy the numerical value for H measured in Sv may be different[36]
Conversion of units 27
Software toolsHome and office computers come with converters in bundled spreadsheet applications or can access free convertersvia the Internet Units and measurements can be easily converted using these tools but only if the units are explicitlydefined and the conversion is compatible (eg cmHg to kPa)
Free conversion softwarebull Units (software) a popular cross-platform command-line utilitybull Converter [37] contextual unit converter for Mozilla Firefox browsersbull Converber [38] portable application converting utilitybull calculla [39] calculla - online web convertersbull iMetrix [40] - unit converter for xpbull uniteasy [41] online scientific unit conversionbull Unit Converter Add-in for Excel [42] - allow a large selection of unit conversions within the Microsoft Excel
spread sheet programbull Unit Converter [43] simple and extensible unit converterbull Portable Unit Converter [44] including 4500 units 33 unit-categories and the possibility to create custom units
General commercial sources of convertersbull Advanced electronic calculators have unit-conversion functionalitybull Spreadsheet programs usually provide conversion functions or formulas or the user can write their ownbull Commercial mathematical scientific and technical applications often include converters
See also
bull Accuracy and precisionbull English unitsbull False precisionbull Imperial unitsbull International System of Unitsbull Mesures usuellesbull Metric system
bull Natural unitsbull Roundingbull Significant figuresbull Temperature conversionbull United States customary unitsbull Units conversion by factor-labelbull Units of measurement
External linksbull British law Units of measurement regulations 1995 [45]
bull ConvertBuster [46] Variety of conversion tools to convert easilybull How Many A dictionary of units of measurement [47]
bull NIST Fundamental physical constants mdash Non-SI units [48]PDF (357 KB)bull NIST Guide to SI Units [49] Many conversion factors listedbull Online Conversion Calculators [50] Very extensive list of conversions from-to equvalent unitsbull The Unified Code for Units of Measure [51]
bull Units Symbols and Conversions XML Dictionary [52]
bull Multilingual Online Conversion of Units [53]
bull Temperature Converter [54]
Conversion of units 28
References[1] United States Naval Observatory (2009) Selected Astronomical Constants 2009 (http asa usno navy mil SecK 2009
Astronomical_Constants_2009 txt) Accessed May 10 2009[2] NIST Reference on Constants Units and Uncertainty (http physics nist gov cgi-bin cuu Valuebohrrada0|search_for=Bohr+
radius)(2006) National Institute of Standards and Technology Retrieved February 22 2008[3] National Institute of Standards and Technology General Tables of Units of Measurement (http ts nist gov WeightsAndMeasures
Publications appxc cfm)[4] Lide D (Ed) (1990) Handbook of Chemistry and Physics (71st ed) Boca Raton FL CRC Press Section 1[5] National Bureau of Standards (June 30 1959) Refinement of values for the yard and the pound Federal Register viewed September 20
2006 at National Geodetic Survey web site (http www ngs noaa gov PUBS_LIB FedRegister FRdoc59-5442 pdf)[6] The International Astronomical Union and Astronomical Units (http www iau org public_press themes measuring )[7] Klein Herbert Arthur (1988) The Science of Measurement a Historical Survey Mineola NY Dover Publications 0-4862-5839-4[8] The International System of Units Section 21 (http www bipm org en si si_brochure chapter2 2-1 ) (8 ed) Bureau International des
Poids et Mesures 2006 retrieved August 26 2009[9] International System of Units (http www bipm org en si si_brochure chapter4 table8 html) 8th ed (2006) Bureau International des
Poids et Mesures Section 41 Table 8[10] P Kenneth Seidelmann Ed (1992) Explanatory Supplement to the Astronomical Almanac Sausalito CA University Science Books p 716
and sv parsec in Glossary[11] Whitelaw Ian (2007) A Measure of All Things The Story of Man and Measurement (http books google com
booksid=3zgGEWM5-iAC) New York Macmillan 0-312-37026-1 p 152[12] De Vinne Theodore Low (1900) The practice of typography a treatise on the processes of type-making the point system the names sizes
styles and prices of plain printing types (http books google com booksid=R4-DjphIpLMC) 2nd ed New York The Century Co p142ndash150
[13] Pasko Wesley Washington (1894) American dictionary of printing and bookmaking (http books google combooksid=Z_QUAAAAIAAJ) (1894) New York Howard Lockwood p 521
[14] Rowlett Russ (2005) How Many A Dictionary of Units of Measurement (http www unc edu ~rowlett units index html)[15] Thompson A and Taylor BN (2008) Guide for the Use of the International System of Units (SI) National Institute of Standards and
Technology Special Publication 811 p 57[16] US Code of Federal Regulations Title 21 Section 1019 Paragraph (b)(5)(viii) (http ecfr gpoaccess gov cgi t text text-idxc=ecframp
rgn=div8amp view=textamp node=212 0 1 1 2 1 1 6amp idno=21) retrieved August 29 2009[17] Barry N Taylor Ed NIST Special Publication 330 The International System of Units (SI) (http physics nist gov Pubs SP330 sp330
pdf) (2001 Edition) Washington US Government Printing Office 43The 12th Conference Generale des Poids et Mesures(CGPM)hellipdeclares that the word ldquolitrerdquo may be employed as a special name for the cubic decimetre
[18] CODATA Value atomic uint of mass (http physics nist gov cgi-bin cuu Valuettme|search_for=atomic+ unit+ of+ mass) (2006)National Institute of Standards and Technology Retrieved 16 September 2008
[19] The Swiss Federal Office for Metrology gives Zentner on a German language web page (http www metas ch de scales systemch html)and quintal on the English translation of that page (http www metas ch en scales systemch html) the unit is marked speacutecifiquementsuisse
[20] Pedersen O (1983) Glossary in Coyne G Hoskin M and Pedersen O Gregorian Reform of the Calendar Proceedings of the VaticanConference to Commemorate its 400th Anniversary Vatican Observatory Available from Astrophysics Data System
[21] Richards EG (1998) Mapping Time Oxford University Press pp 94ndash95 ISBN 0-19-850413-6[22] Steel Duncan (2000) Marking Time John Wiley amp Sons p 46 ISBN 0-471-29827-1[23] CODATA Value atomic unit of force (http physics nist gov cuu Constants ) (2006) National Institute of Standards and Technology
Retrieved September 14 2008[24] [[Comiteacute International des Poids et Mesures (http www bipm org en CIPM db 1946 2 )] Resolution 2] 1946 retrieved August 26
2009[25] Barry N Taylor (April 1995) Guide for the Use of the International System of Units (SI) (http physics nist gov cuu pdf sp811 pdf)
(NIST Special Publication 811) Washington DC US Government Printing Office pp 57ndash68[26] Barry N Taylor (April 1995) Guide for the Use of the International System of Units (SI) (NIST Special Publication 811) Washington DC
US Government Printing Office p 5[27] International System of Units (http www bipm org en si si_brochure chapter4 table7 html) 8th ed (2006) Bureau International des
Poids et Mesures Section 41 Table 7[28] The NIST Reference on Constants Units and Uncertainty (http physics nist gov cgi-bin cuu Valueauedm) 2006 retrieved August
26 2009[29] NIST Guide to SI Units Appendix B9 (http physics nist gov Pubs SP811 appenB9 html) retrieved August 27 2009[30] Standard for the Use of the International System of Units (SI) The Modern Metric System IEEEASTM SI 10-1997 (1997) New York and
West Conshohocken PA Institute of Electrical and Electronics Engineers and American Society for Testing and Materials Tables A1through A5
Conversion of units 29
[31] The NIST Reference on Constants Units and Uncertainty (http physics nist gov cuu Units candela html) retrieved August 28 2009[32] Ambler Thompson amp Barry N Taylor (2008) Guide for the Use of the International System of Units (SI) (http physics nist gov cuu
pdf sp811 pdf) Special Publication 811 Gaithersburg MD National Institute of Standards and Technology p 10[33] The International System of Units Section 222 Table 3 (http www bipm org en si si_brochure chapter2 2-2 table3 html) (8 ed)
Bureau International des Poids et Mesures 2006 retrieved August 27 2009[34] The NIST Guide to the SI (Special Publication 811) section 52 (http physics nist gov Pubs SP811 sec05 html5 2) 2008 retrieved
August 27 2009[35] Ambler Thompson amp Barry N Taylor (2008) Guide for the Use of the International System of Units (SI) (http physics nist gov cuu
pdf sp811 pdf) Special Publication 811 Gaithersburg MD National Institute of Standards and Technology p 5[36] [[Comiteacute international des poids et mesures (http www bipm org en CIPM db 2002 2 )] 2002 Recommendation 2] retrieved
August 27 2009[37] http converter mozdev org[38] http www xyntec com converber htm[39] http www calculla com[40] http illusions hu index phptask=100amp lang=0amp statpage=86[41] http www uniteasy com[42] http www tenderwire com wikipedialandingpage[43] http www kamlex com index phpoption=com_contentamp view=articleamp id=53amp Itemid=55[44] http www sttmedia com unitconverter[45] http www hmso gov uk si si1995 Uksi_19951804_en_2 htm[46] http www convertbuster com[47] http www unc edu ~rowlett units[48] http physics nist gov cuu Document nonsi_in_1998 pdf[49] http physics nist gov Pubs SP811 appenB9 html[50] http www onlineconversion com[51] http aurora rg iupui edu ~schadow units UCUM ucum html[52] http www posc org refs poscUnits20 xml[53] http www imperialtometric com[54] http www tampile com
Article Sources and Contributors 30
Article Sources and ContributorsConversion of units Source httpenwikipediaorgwindexphpoldid=373975089 Contributors 1571781xxx 7 A-giau AVSI Acather96 Ahoerstemeier Alexius08 Altenmann AndreEngels Andrewa Andy120290 Anonymi Ariconte Army1987 ArnoldReinhold Arthur3030 Aspects AxelBoldt AzaToth Azikala BW95 Bdesham Beland Bensaccount Bkumartvm Blackand White BlaiseFEgan BlueEarth Bobblewik Borbrav Bpmullins Bryan Derksen C J B Scholten CORNELIUSSEON CTZMSC3 Calltech Camerajohn Chaosfeary Charles MatthewsChris the speller Cmdrjameson Colonies Chris Conversion script Cope555 Crappy13 Crissov CyrilB DARTH SIDIOUS 2 DMacks DanielCD Dark Formal DarkestSideX DekisugiDenelson83 Dhp1080 Dicklyon DirkvdM Donald Duck Donarreiskoffer Dramatic Dyss DAringsbquougosz Egil Ehrenkater Ejohnsonboulder Elexmax Elf Emokhberi Enon Eob Epbr123Euchiasmus Fathead99 Father Goose Fella22 Femto FernandoAC Fibula Flutefreek Fred Bauder Fredrik Fuhghettaboutit Fuzheado Gaff Gene Nygaard Georgiy1996 Gerry AshtonGiftlite Gilliam Glenn L GoingBatty Goobergunch Gregsexton Greyengine5 Grunt Gurch Gutza HLHJ Haemo Hammersbach Heracles31 Herbee Heron HikerBush Hqb IcairnsIgiffin Indefatigable Isis JBobbitt JHunterJ Jabowery JakeVortex Jamicanmonkey Jason Begin Jay Jc3s5h Jcronen1 Jdoherty Jeffz1 Jeronimo Jimmuhk Jimp Jimwilliams57 JoeinwapJohndburger Josh Parris Jq4bagiq Kaihsu KaneWang Keenan Pepper Kevin Rector KeyStorm Khukri Kurtan Lee Daniel Crocker LightYear Linuxoidoz Liv4christ210 Loggie Lolo252Lupinelawyer M ichaeligl MJCdetroit MTC Mac MacMcF Magore Markus Kuhn Masterqwe MaxHund Maxamegalon2000 Mbeychok Meggar Mh26 Michael Daly Michael Hardy MichelAudy Mikelifeguard Mikhailov Kusserow Mindbuilder Missvain Monger Mr bulow MrOllie MrZhuKeeper Muro de Aguas Mwanner Mwtoews Nandesuka Natkeeran Ndsg NgjaimeNhy67ygv Nick Y Nick123 NickPenguin Ninjagecko Noe Nosilleg Now3r3 Obelix homologator Oldadamml Oleg Alexandrov Olivier Ortolan88 OwenBlacker Pac72 PassargeaPatrick Paul Martin Peter Horn Physchim62 Piels Pierdm Pmanderson Prometheus235 Quadell QuantumEleven Quod erat demonstrandum 314159 Radagast83 Rccoms RedWolfReinyday Revipm Rexparry sydney Reyk Rhetth Rhialto Rich Farmbrough Richard Myers Rjwilmsi Rlsheehan Robin Barry RoySmith Rpwolfgram SD6-Agent SGBailey SamuelLowry Samw Sander123 Seabhcan SebastianHelm Sherbert1 Shinhan Shrew Sietse Snel SimonP Sinbaddasail0r Skotte Smalljim SomeHuman Spencer Srleffler StarwarsmastergeekSteacoon StefanK SteveRamone Stevertigo Stokerm Suisui Sunev Superboy112233 Superm401 Synchronism Tacoman1996 Tarquin Taw Teratornis The Man in Question ThierrycThingg Thinking of England Thunderbird2 Timwi Tobias Hoevekamp Tomasr Tonsofpcs Toon05 Topsykretts2512 Trekphiler Tuwile Twanvl Uday147502 Unitman00 UrhixidurUtherSRG Vargenau Vsmith WarrenPlatts Wasell Welsh Whispering Wikinger Wolfkeeper Wtmitchell XJamRastafire Xenonice Yath Zginder Zibem Zocky Zotel 713 anonymousedits
Name of unit Symbol Definition Relation to SI units
lumen (SIunit)
lm equiv cdmiddotsr = 1 lm = 1 cdmiddotsr
Illuminance
Illuminance
Name of unit Symbol Definition Relation to SI units
footcandle lumen per square foot fc equiv lmft2 = 10763910417 lx
lumen per square inch lmin2 equiv lmin2 asymp 15500031 lx
lux (SI unit) lx equiv lmm2 = 1 lx = 1 lmm2
phot (CGS unit) ph equiv lmcm2 = 1 times 104 lx
Radiation - source activity
Conversion of units 26
Radioactivity
Name of unit Symbol Definition Relation to SI units
becquerel (SIunit)
Bq equiv Number of disintegrations per second = 1 Bq = 1s
curie Ci equiv 37 times 1010 Bq = 37 times 1010 Bq [32]
rutherford (H) rd equiv 1 MBq = 1 times 106 Bq
Please note that although becquerel (Bq) and hertz (Hz) both ultimately refer to the same SI base unit (sminus1) Hz isused only for periodic phenomena and Bq is only used for stochastic processes associated with radioactivity[33]
Radiation - exposure
Radiation - exposure
Name of unit Symbol Definition Relation to SI units
roentgen R 1 R equiv 258 times 10minus4 Ckg[29] = 258 times 10minus4 Ckg
The roentgen is not a SI unit and the NIST strongly discourages its continued use[34]
Radiation - absorbed dose
Radiation - absorbed dose
Name of unit Symbol Definition Relation to SI units
Name of unit Symbol Definition Relation to SI units
Roumlntgen equivalent man rem equiv 001 Sv = 001 Sv
sievert (SI unit) Sv equiv 1 Jkg[33] = 1 Sv
Although the definitions for sievert (Sv) and gray (Gy) would seem to indicate that they measure the same quantitiesthis is not the case The effect of receiving a certain dose of radiation (given as Gy) is variable and depends on manyfactors thus a new unit was needed to denote the biological effectiveness of that dose on the body this is known asthe equivalent dose and is shown in Sv The general relationship between absorbed dose and equivalent dose can berepresented as
H = Q middot D
where H is the equivalent dose D is the absorbed dose and Q is a dimensionless quality factor Thus for anyquantity of D measured in Gy the numerical value for H measured in Sv may be different[36]
Conversion of units 27
Software toolsHome and office computers come with converters in bundled spreadsheet applications or can access free convertersvia the Internet Units and measurements can be easily converted using these tools but only if the units are explicitlydefined and the conversion is compatible (eg cmHg to kPa)
Free conversion softwarebull Units (software) a popular cross-platform command-line utilitybull Converter [37] contextual unit converter for Mozilla Firefox browsersbull Converber [38] portable application converting utilitybull calculla [39] calculla - online web convertersbull iMetrix [40] - unit converter for xpbull uniteasy [41] online scientific unit conversionbull Unit Converter Add-in for Excel [42] - allow a large selection of unit conversions within the Microsoft Excel
spread sheet programbull Unit Converter [43] simple and extensible unit converterbull Portable Unit Converter [44] including 4500 units 33 unit-categories and the possibility to create custom units
General commercial sources of convertersbull Advanced electronic calculators have unit-conversion functionalitybull Spreadsheet programs usually provide conversion functions or formulas or the user can write their ownbull Commercial mathematical scientific and technical applications often include converters
See also
bull Accuracy and precisionbull English unitsbull False precisionbull Imperial unitsbull International System of Unitsbull Mesures usuellesbull Metric system
bull Natural unitsbull Roundingbull Significant figuresbull Temperature conversionbull United States customary unitsbull Units conversion by factor-labelbull Units of measurement
External linksbull British law Units of measurement regulations 1995 [45]
bull ConvertBuster [46] Variety of conversion tools to convert easilybull How Many A dictionary of units of measurement [47]
bull NIST Fundamental physical constants mdash Non-SI units [48]PDF (357 KB)bull NIST Guide to SI Units [49] Many conversion factors listedbull Online Conversion Calculators [50] Very extensive list of conversions from-to equvalent unitsbull The Unified Code for Units of Measure [51]
bull Units Symbols and Conversions XML Dictionary [52]
bull Multilingual Online Conversion of Units [53]
bull Temperature Converter [54]
Conversion of units 28
References[1] United States Naval Observatory (2009) Selected Astronomical Constants 2009 (http asa usno navy mil SecK 2009
Astronomical_Constants_2009 txt) Accessed May 10 2009[2] NIST Reference on Constants Units and Uncertainty (http physics nist gov cgi-bin cuu Valuebohrrada0|search_for=Bohr+
radius)(2006) National Institute of Standards and Technology Retrieved February 22 2008[3] National Institute of Standards and Technology General Tables of Units of Measurement (http ts nist gov WeightsAndMeasures
Publications appxc cfm)[4] Lide D (Ed) (1990) Handbook of Chemistry and Physics (71st ed) Boca Raton FL CRC Press Section 1[5] National Bureau of Standards (June 30 1959) Refinement of values for the yard and the pound Federal Register viewed September 20
2006 at National Geodetic Survey web site (http www ngs noaa gov PUBS_LIB FedRegister FRdoc59-5442 pdf)[6] The International Astronomical Union and Astronomical Units (http www iau org public_press themes measuring )[7] Klein Herbert Arthur (1988) The Science of Measurement a Historical Survey Mineola NY Dover Publications 0-4862-5839-4[8] The International System of Units Section 21 (http www bipm org en si si_brochure chapter2 2-1 ) (8 ed) Bureau International des
Poids et Mesures 2006 retrieved August 26 2009[9] International System of Units (http www bipm org en si si_brochure chapter4 table8 html) 8th ed (2006) Bureau International des
Poids et Mesures Section 41 Table 8[10] P Kenneth Seidelmann Ed (1992) Explanatory Supplement to the Astronomical Almanac Sausalito CA University Science Books p 716
and sv parsec in Glossary[11] Whitelaw Ian (2007) A Measure of All Things The Story of Man and Measurement (http books google com
booksid=3zgGEWM5-iAC) New York Macmillan 0-312-37026-1 p 152[12] De Vinne Theodore Low (1900) The practice of typography a treatise on the processes of type-making the point system the names sizes
styles and prices of plain printing types (http books google com booksid=R4-DjphIpLMC) 2nd ed New York The Century Co p142ndash150
[13] Pasko Wesley Washington (1894) American dictionary of printing and bookmaking (http books google combooksid=Z_QUAAAAIAAJ) (1894) New York Howard Lockwood p 521
[14] Rowlett Russ (2005) How Many A Dictionary of Units of Measurement (http www unc edu ~rowlett units index html)[15] Thompson A and Taylor BN (2008) Guide for the Use of the International System of Units (SI) National Institute of Standards and
Technology Special Publication 811 p 57[16] US Code of Federal Regulations Title 21 Section 1019 Paragraph (b)(5)(viii) (http ecfr gpoaccess gov cgi t text text-idxc=ecframp
rgn=div8amp view=textamp node=212 0 1 1 2 1 1 6amp idno=21) retrieved August 29 2009[17] Barry N Taylor Ed NIST Special Publication 330 The International System of Units (SI) (http physics nist gov Pubs SP330 sp330
pdf) (2001 Edition) Washington US Government Printing Office 43The 12th Conference Generale des Poids et Mesures(CGPM)hellipdeclares that the word ldquolitrerdquo may be employed as a special name for the cubic decimetre
[18] CODATA Value atomic uint of mass (http physics nist gov cgi-bin cuu Valuettme|search_for=atomic+ unit+ of+ mass) (2006)National Institute of Standards and Technology Retrieved 16 September 2008
[19] The Swiss Federal Office for Metrology gives Zentner on a German language web page (http www metas ch de scales systemch html)and quintal on the English translation of that page (http www metas ch en scales systemch html) the unit is marked speacutecifiquementsuisse
[20] Pedersen O (1983) Glossary in Coyne G Hoskin M and Pedersen O Gregorian Reform of the Calendar Proceedings of the VaticanConference to Commemorate its 400th Anniversary Vatican Observatory Available from Astrophysics Data System
[21] Richards EG (1998) Mapping Time Oxford University Press pp 94ndash95 ISBN 0-19-850413-6[22] Steel Duncan (2000) Marking Time John Wiley amp Sons p 46 ISBN 0-471-29827-1[23] CODATA Value atomic unit of force (http physics nist gov cuu Constants ) (2006) National Institute of Standards and Technology
Retrieved September 14 2008[24] [[Comiteacute International des Poids et Mesures (http www bipm org en CIPM db 1946 2 )] Resolution 2] 1946 retrieved August 26
2009[25] Barry N Taylor (April 1995) Guide for the Use of the International System of Units (SI) (http physics nist gov cuu pdf sp811 pdf)
(NIST Special Publication 811) Washington DC US Government Printing Office pp 57ndash68[26] Barry N Taylor (April 1995) Guide for the Use of the International System of Units (SI) (NIST Special Publication 811) Washington DC
US Government Printing Office p 5[27] International System of Units (http www bipm org en si si_brochure chapter4 table7 html) 8th ed (2006) Bureau International des
Poids et Mesures Section 41 Table 7[28] The NIST Reference on Constants Units and Uncertainty (http physics nist gov cgi-bin cuu Valueauedm) 2006 retrieved August
26 2009[29] NIST Guide to SI Units Appendix B9 (http physics nist gov Pubs SP811 appenB9 html) retrieved August 27 2009[30] Standard for the Use of the International System of Units (SI) The Modern Metric System IEEEASTM SI 10-1997 (1997) New York and
West Conshohocken PA Institute of Electrical and Electronics Engineers and American Society for Testing and Materials Tables A1through A5
Conversion of units 29
[31] The NIST Reference on Constants Units and Uncertainty (http physics nist gov cuu Units candela html) retrieved August 28 2009[32] Ambler Thompson amp Barry N Taylor (2008) Guide for the Use of the International System of Units (SI) (http physics nist gov cuu
pdf sp811 pdf) Special Publication 811 Gaithersburg MD National Institute of Standards and Technology p 10[33] The International System of Units Section 222 Table 3 (http www bipm org en si si_brochure chapter2 2-2 table3 html) (8 ed)
Bureau International des Poids et Mesures 2006 retrieved August 27 2009[34] The NIST Guide to the SI (Special Publication 811) section 52 (http physics nist gov Pubs SP811 sec05 html5 2) 2008 retrieved
August 27 2009[35] Ambler Thompson amp Barry N Taylor (2008) Guide for the Use of the International System of Units (SI) (http physics nist gov cuu
pdf sp811 pdf) Special Publication 811 Gaithersburg MD National Institute of Standards and Technology p 5[36] [[Comiteacute international des poids et mesures (http www bipm org en CIPM db 2002 2 )] 2002 Recommendation 2] retrieved
August 27 2009[37] http converter mozdev org[38] http www xyntec com converber htm[39] http www calculla com[40] http illusions hu index phptask=100amp lang=0amp statpage=86[41] http www uniteasy com[42] http www tenderwire com wikipedialandingpage[43] http www kamlex com index phpoption=com_contentamp view=articleamp id=53amp Itemid=55[44] http www sttmedia com unitconverter[45] http www hmso gov uk si si1995 Uksi_19951804_en_2 htm[46] http www convertbuster com[47] http www unc edu ~rowlett units[48] http physics nist gov cuu Document nonsi_in_1998 pdf[49] http physics nist gov Pubs SP811 appenB9 html[50] http www onlineconversion com[51] http aurora rg iupui edu ~schadow units UCUM ucum html[52] http www posc org refs poscUnits20 xml[53] http www imperialtometric com[54] http www tampile com
Article Sources and Contributors 30
Article Sources and ContributorsConversion of units Source httpenwikipediaorgwindexphpoldid=373975089 Contributors 1571781xxx 7 A-giau AVSI Acather96 Ahoerstemeier Alexius08 Altenmann AndreEngels Andrewa Andy120290 Anonymi Ariconte Army1987 ArnoldReinhold Arthur3030 Aspects AxelBoldt AzaToth Azikala BW95 Bdesham Beland Bensaccount Bkumartvm Blackand White BlaiseFEgan BlueEarth Bobblewik Borbrav Bpmullins Bryan Derksen C J B Scholten CORNELIUSSEON CTZMSC3 Calltech Camerajohn Chaosfeary Charles MatthewsChris the speller Cmdrjameson Colonies Chris Conversion script Cope555 Crappy13 Crissov CyrilB DARTH SIDIOUS 2 DMacks DanielCD Dark Formal DarkestSideX DekisugiDenelson83 Dhp1080 Dicklyon DirkvdM Donald Duck Donarreiskoffer Dramatic Dyss DAringsbquougosz Egil Ehrenkater Ejohnsonboulder Elexmax Elf Emokhberi Enon Eob Epbr123Euchiasmus Fathead99 Father Goose Fella22 Femto FernandoAC Fibula Flutefreek Fred Bauder Fredrik Fuhghettaboutit Fuzheado Gaff Gene Nygaard Georgiy1996 Gerry AshtonGiftlite Gilliam Glenn L GoingBatty Goobergunch Gregsexton Greyengine5 Grunt Gurch Gutza HLHJ Haemo Hammersbach Heracles31 Herbee Heron HikerBush Hqb IcairnsIgiffin Indefatigable Isis JBobbitt JHunterJ Jabowery JakeVortex Jamicanmonkey Jason Begin Jay Jc3s5h Jcronen1 Jdoherty Jeffz1 Jeronimo Jimmuhk Jimp Jimwilliams57 JoeinwapJohndburger Josh Parris Jq4bagiq Kaihsu KaneWang Keenan Pepper Kevin Rector KeyStorm Khukri Kurtan Lee Daniel Crocker LightYear Linuxoidoz Liv4christ210 Loggie Lolo252Lupinelawyer M ichaeligl MJCdetroit MTC Mac MacMcF Magore Markus Kuhn Masterqwe MaxHund Maxamegalon2000 Mbeychok Meggar Mh26 Michael Daly Michael Hardy MichelAudy Mikelifeguard Mikhailov Kusserow Mindbuilder Missvain Monger Mr bulow MrOllie MrZhuKeeper Muro de Aguas Mwanner Mwtoews Nandesuka Natkeeran Ndsg NgjaimeNhy67ygv Nick Y Nick123 NickPenguin Ninjagecko Noe Nosilleg Now3r3 Obelix homologator Oldadamml Oleg Alexandrov Olivier Ortolan88 OwenBlacker Pac72 PassargeaPatrick Paul Martin Peter Horn Physchim62 Piels Pierdm Pmanderson Prometheus235 Quadell QuantumEleven Quod erat demonstrandum 314159 Radagast83 Rccoms RedWolfReinyday Revipm Rexparry sydney Reyk Rhetth Rhialto Rich Farmbrough Richard Myers Rjwilmsi Rlsheehan Robin Barry RoySmith Rpwolfgram SD6-Agent SGBailey SamuelLowry Samw Sander123 Seabhcan SebastianHelm Sherbert1 Shinhan Shrew Sietse Snel SimonP Sinbaddasail0r Skotte Smalljim SomeHuman Spencer Srleffler StarwarsmastergeekSteacoon StefanK SteveRamone Stevertigo Stokerm Suisui Sunev Superboy112233 Superm401 Synchronism Tacoman1996 Tarquin Taw Teratornis The Man in Question ThierrycThingg Thinking of England Thunderbird2 Timwi Tobias Hoevekamp Tomasr Tonsofpcs Toon05 Topsykretts2512 Trekphiler Tuwile Twanvl Uday147502 Unitman00 UrhixidurUtherSRG Vargenau Vsmith WarrenPlatts Wasell Welsh Whispering Wikinger Wolfkeeper Wtmitchell XJamRastafire Xenonice Yath Zginder Zibem Zocky Zotel 713 anonymousedits
Name of unit Symbol Definition Relation to SI units
becquerel (SIunit)
Bq equiv Number of disintegrations per second = 1 Bq = 1s
curie Ci equiv 37 times 1010 Bq = 37 times 1010 Bq [32]
rutherford (H) rd equiv 1 MBq = 1 times 106 Bq
Please note that although becquerel (Bq) and hertz (Hz) both ultimately refer to the same SI base unit (sminus1) Hz isused only for periodic phenomena and Bq is only used for stochastic processes associated with radioactivity[33]
Radiation - exposure
Radiation - exposure
Name of unit Symbol Definition Relation to SI units
roentgen R 1 R equiv 258 times 10minus4 Ckg[29] = 258 times 10minus4 Ckg
The roentgen is not a SI unit and the NIST strongly discourages its continued use[34]
Radiation - absorbed dose
Radiation - absorbed dose
Name of unit Symbol Definition Relation to SI units
Name of unit Symbol Definition Relation to SI units
Roumlntgen equivalent man rem equiv 001 Sv = 001 Sv
sievert (SI unit) Sv equiv 1 Jkg[33] = 1 Sv
Although the definitions for sievert (Sv) and gray (Gy) would seem to indicate that they measure the same quantitiesthis is not the case The effect of receiving a certain dose of radiation (given as Gy) is variable and depends on manyfactors thus a new unit was needed to denote the biological effectiveness of that dose on the body this is known asthe equivalent dose and is shown in Sv The general relationship between absorbed dose and equivalent dose can berepresented as
H = Q middot D
where H is the equivalent dose D is the absorbed dose and Q is a dimensionless quality factor Thus for anyquantity of D measured in Gy the numerical value for H measured in Sv may be different[36]
Conversion of units 27
Software toolsHome and office computers come with converters in bundled spreadsheet applications or can access free convertersvia the Internet Units and measurements can be easily converted using these tools but only if the units are explicitlydefined and the conversion is compatible (eg cmHg to kPa)
Free conversion softwarebull Units (software) a popular cross-platform command-line utilitybull Converter [37] contextual unit converter for Mozilla Firefox browsersbull Converber [38] portable application converting utilitybull calculla [39] calculla - online web convertersbull iMetrix [40] - unit converter for xpbull uniteasy [41] online scientific unit conversionbull Unit Converter Add-in for Excel [42] - allow a large selection of unit conversions within the Microsoft Excel
spread sheet programbull Unit Converter [43] simple and extensible unit converterbull Portable Unit Converter [44] including 4500 units 33 unit-categories and the possibility to create custom units
General commercial sources of convertersbull Advanced electronic calculators have unit-conversion functionalitybull Spreadsheet programs usually provide conversion functions or formulas or the user can write their ownbull Commercial mathematical scientific and technical applications often include converters
See also
bull Accuracy and precisionbull English unitsbull False precisionbull Imperial unitsbull International System of Unitsbull Mesures usuellesbull Metric system
bull Natural unitsbull Roundingbull Significant figuresbull Temperature conversionbull United States customary unitsbull Units conversion by factor-labelbull Units of measurement
External linksbull British law Units of measurement regulations 1995 [45]
bull ConvertBuster [46] Variety of conversion tools to convert easilybull How Many A dictionary of units of measurement [47]
bull NIST Fundamental physical constants mdash Non-SI units [48]PDF (357 KB)bull NIST Guide to SI Units [49] Many conversion factors listedbull Online Conversion Calculators [50] Very extensive list of conversions from-to equvalent unitsbull The Unified Code for Units of Measure [51]
bull Units Symbols and Conversions XML Dictionary [52]
bull Multilingual Online Conversion of Units [53]
bull Temperature Converter [54]
Conversion of units 28
References[1] United States Naval Observatory (2009) Selected Astronomical Constants 2009 (http asa usno navy mil SecK 2009
Astronomical_Constants_2009 txt) Accessed May 10 2009[2] NIST Reference on Constants Units and Uncertainty (http physics nist gov cgi-bin cuu Valuebohrrada0|search_for=Bohr+
radius)(2006) National Institute of Standards and Technology Retrieved February 22 2008[3] National Institute of Standards and Technology General Tables of Units of Measurement (http ts nist gov WeightsAndMeasures
Publications appxc cfm)[4] Lide D (Ed) (1990) Handbook of Chemistry and Physics (71st ed) Boca Raton FL CRC Press Section 1[5] National Bureau of Standards (June 30 1959) Refinement of values for the yard and the pound Federal Register viewed September 20
2006 at National Geodetic Survey web site (http www ngs noaa gov PUBS_LIB FedRegister FRdoc59-5442 pdf)[6] The International Astronomical Union and Astronomical Units (http www iau org public_press themes measuring )[7] Klein Herbert Arthur (1988) The Science of Measurement a Historical Survey Mineola NY Dover Publications 0-4862-5839-4[8] The International System of Units Section 21 (http www bipm org en si si_brochure chapter2 2-1 ) (8 ed) Bureau International des
Poids et Mesures 2006 retrieved August 26 2009[9] International System of Units (http www bipm org en si si_brochure chapter4 table8 html) 8th ed (2006) Bureau International des
Poids et Mesures Section 41 Table 8[10] P Kenneth Seidelmann Ed (1992) Explanatory Supplement to the Astronomical Almanac Sausalito CA University Science Books p 716
and sv parsec in Glossary[11] Whitelaw Ian (2007) A Measure of All Things The Story of Man and Measurement (http books google com
booksid=3zgGEWM5-iAC) New York Macmillan 0-312-37026-1 p 152[12] De Vinne Theodore Low (1900) The practice of typography a treatise on the processes of type-making the point system the names sizes
styles and prices of plain printing types (http books google com booksid=R4-DjphIpLMC) 2nd ed New York The Century Co p142ndash150
[13] Pasko Wesley Washington (1894) American dictionary of printing and bookmaking (http books google combooksid=Z_QUAAAAIAAJ) (1894) New York Howard Lockwood p 521
[14] Rowlett Russ (2005) How Many A Dictionary of Units of Measurement (http www unc edu ~rowlett units index html)[15] Thompson A and Taylor BN (2008) Guide for the Use of the International System of Units (SI) National Institute of Standards and
Technology Special Publication 811 p 57[16] US Code of Federal Regulations Title 21 Section 1019 Paragraph (b)(5)(viii) (http ecfr gpoaccess gov cgi t text text-idxc=ecframp
rgn=div8amp view=textamp node=212 0 1 1 2 1 1 6amp idno=21) retrieved August 29 2009[17] Barry N Taylor Ed NIST Special Publication 330 The International System of Units (SI) (http physics nist gov Pubs SP330 sp330
pdf) (2001 Edition) Washington US Government Printing Office 43The 12th Conference Generale des Poids et Mesures(CGPM)hellipdeclares that the word ldquolitrerdquo may be employed as a special name for the cubic decimetre
[18] CODATA Value atomic uint of mass (http physics nist gov cgi-bin cuu Valuettme|search_for=atomic+ unit+ of+ mass) (2006)National Institute of Standards and Technology Retrieved 16 September 2008
[19] The Swiss Federal Office for Metrology gives Zentner on a German language web page (http www metas ch de scales systemch html)and quintal on the English translation of that page (http www metas ch en scales systemch html) the unit is marked speacutecifiquementsuisse
[20] Pedersen O (1983) Glossary in Coyne G Hoskin M and Pedersen O Gregorian Reform of the Calendar Proceedings of the VaticanConference to Commemorate its 400th Anniversary Vatican Observatory Available from Astrophysics Data System
[21] Richards EG (1998) Mapping Time Oxford University Press pp 94ndash95 ISBN 0-19-850413-6[22] Steel Duncan (2000) Marking Time John Wiley amp Sons p 46 ISBN 0-471-29827-1[23] CODATA Value atomic unit of force (http physics nist gov cuu Constants ) (2006) National Institute of Standards and Technology
Retrieved September 14 2008[24] [[Comiteacute International des Poids et Mesures (http www bipm org en CIPM db 1946 2 )] Resolution 2] 1946 retrieved August 26
2009[25] Barry N Taylor (April 1995) Guide for the Use of the International System of Units (SI) (http physics nist gov cuu pdf sp811 pdf)
(NIST Special Publication 811) Washington DC US Government Printing Office pp 57ndash68[26] Barry N Taylor (April 1995) Guide for the Use of the International System of Units (SI) (NIST Special Publication 811) Washington DC
US Government Printing Office p 5[27] International System of Units (http www bipm org en si si_brochure chapter4 table7 html) 8th ed (2006) Bureau International des
Poids et Mesures Section 41 Table 7[28] The NIST Reference on Constants Units and Uncertainty (http physics nist gov cgi-bin cuu Valueauedm) 2006 retrieved August
26 2009[29] NIST Guide to SI Units Appendix B9 (http physics nist gov Pubs SP811 appenB9 html) retrieved August 27 2009[30] Standard for the Use of the International System of Units (SI) The Modern Metric System IEEEASTM SI 10-1997 (1997) New York and
West Conshohocken PA Institute of Electrical and Electronics Engineers and American Society for Testing and Materials Tables A1through A5
Conversion of units 29
[31] The NIST Reference on Constants Units and Uncertainty (http physics nist gov cuu Units candela html) retrieved August 28 2009[32] Ambler Thompson amp Barry N Taylor (2008) Guide for the Use of the International System of Units (SI) (http physics nist gov cuu
pdf sp811 pdf) Special Publication 811 Gaithersburg MD National Institute of Standards and Technology p 10[33] The International System of Units Section 222 Table 3 (http www bipm org en si si_brochure chapter2 2-2 table3 html) (8 ed)
Bureau International des Poids et Mesures 2006 retrieved August 27 2009[34] The NIST Guide to the SI (Special Publication 811) section 52 (http physics nist gov Pubs SP811 sec05 html5 2) 2008 retrieved
August 27 2009[35] Ambler Thompson amp Barry N Taylor (2008) Guide for the Use of the International System of Units (SI) (http physics nist gov cuu
pdf sp811 pdf) Special Publication 811 Gaithersburg MD National Institute of Standards and Technology p 5[36] [[Comiteacute international des poids et mesures (http www bipm org en CIPM db 2002 2 )] 2002 Recommendation 2] retrieved
August 27 2009[37] http converter mozdev org[38] http www xyntec com converber htm[39] http www calculla com[40] http illusions hu index phptask=100amp lang=0amp statpage=86[41] http www uniteasy com[42] http www tenderwire com wikipedialandingpage[43] http www kamlex com index phpoption=com_contentamp view=articleamp id=53amp Itemid=55[44] http www sttmedia com unitconverter[45] http www hmso gov uk si si1995 Uksi_19951804_en_2 htm[46] http www convertbuster com[47] http www unc edu ~rowlett units[48] http physics nist gov cuu Document nonsi_in_1998 pdf[49] http physics nist gov Pubs SP811 appenB9 html[50] http www onlineconversion com[51] http aurora rg iupui edu ~schadow units UCUM ucum html[52] http www posc org refs poscUnits20 xml[53] http www imperialtometric com[54] http www tampile com
Article Sources and Contributors 30
Article Sources and ContributorsConversion of units Source httpenwikipediaorgwindexphpoldid=373975089 Contributors 1571781xxx 7 A-giau AVSI Acather96 Ahoerstemeier Alexius08 Altenmann AndreEngels Andrewa Andy120290 Anonymi Ariconte Army1987 ArnoldReinhold Arthur3030 Aspects AxelBoldt AzaToth Azikala BW95 Bdesham Beland Bensaccount Bkumartvm Blackand White BlaiseFEgan BlueEarth Bobblewik Borbrav Bpmullins Bryan Derksen C J B Scholten CORNELIUSSEON CTZMSC3 Calltech Camerajohn Chaosfeary Charles MatthewsChris the speller Cmdrjameson Colonies Chris Conversion script Cope555 Crappy13 Crissov CyrilB DARTH SIDIOUS 2 DMacks DanielCD Dark Formal DarkestSideX DekisugiDenelson83 Dhp1080 Dicklyon DirkvdM Donald Duck Donarreiskoffer Dramatic Dyss DAringsbquougosz Egil Ehrenkater Ejohnsonboulder Elexmax Elf Emokhberi Enon Eob Epbr123Euchiasmus Fathead99 Father Goose Fella22 Femto FernandoAC Fibula Flutefreek Fred Bauder Fredrik Fuhghettaboutit Fuzheado Gaff Gene Nygaard Georgiy1996 Gerry AshtonGiftlite Gilliam Glenn L GoingBatty Goobergunch Gregsexton Greyengine5 Grunt Gurch Gutza HLHJ Haemo Hammersbach Heracles31 Herbee Heron HikerBush Hqb IcairnsIgiffin Indefatigable Isis JBobbitt JHunterJ Jabowery JakeVortex Jamicanmonkey Jason Begin Jay Jc3s5h Jcronen1 Jdoherty Jeffz1 Jeronimo Jimmuhk Jimp Jimwilliams57 JoeinwapJohndburger Josh Parris Jq4bagiq Kaihsu KaneWang Keenan Pepper Kevin Rector KeyStorm Khukri Kurtan Lee Daniel Crocker LightYear Linuxoidoz Liv4christ210 Loggie Lolo252Lupinelawyer M ichaeligl MJCdetroit MTC Mac MacMcF Magore Markus Kuhn Masterqwe MaxHund Maxamegalon2000 Mbeychok Meggar Mh26 Michael Daly Michael Hardy MichelAudy Mikelifeguard Mikhailov Kusserow Mindbuilder Missvain Monger Mr bulow MrOllie MrZhuKeeper Muro de Aguas Mwanner Mwtoews Nandesuka Natkeeran Ndsg NgjaimeNhy67ygv Nick Y Nick123 NickPenguin Ninjagecko Noe Nosilleg Now3r3 Obelix homologator Oldadamml Oleg Alexandrov Olivier Ortolan88 OwenBlacker Pac72 PassargeaPatrick Paul Martin Peter Horn Physchim62 Piels Pierdm Pmanderson Prometheus235 Quadell QuantumEleven Quod erat demonstrandum 314159 Radagast83 Rccoms RedWolfReinyday Revipm Rexparry sydney Reyk Rhetth Rhialto Rich Farmbrough Richard Myers Rjwilmsi Rlsheehan Robin Barry RoySmith Rpwolfgram SD6-Agent SGBailey SamuelLowry Samw Sander123 Seabhcan SebastianHelm Sherbert1 Shinhan Shrew Sietse Snel SimonP Sinbaddasail0r Skotte Smalljim SomeHuman Spencer Srleffler StarwarsmastergeekSteacoon StefanK SteveRamone Stevertigo Stokerm Suisui Sunev Superboy112233 Superm401 Synchronism Tacoman1996 Tarquin Taw Teratornis The Man in Question ThierrycThingg Thinking of England Thunderbird2 Timwi Tobias Hoevekamp Tomasr Tonsofpcs Toon05 Topsykretts2512 Trekphiler Tuwile Twanvl Uday147502 Unitman00 UrhixidurUtherSRG Vargenau Vsmith WarrenPlatts Wasell Welsh Whispering Wikinger Wolfkeeper Wtmitchell XJamRastafire Xenonice Yath Zginder Zibem Zocky Zotel 713 anonymousedits
Software toolsHome and office computers come with converters in bundled spreadsheet applications or can access free convertersvia the Internet Units and measurements can be easily converted using these tools but only if the units are explicitlydefined and the conversion is compatible (eg cmHg to kPa)
Free conversion softwarebull Units (software) a popular cross-platform command-line utilitybull Converter [37] contextual unit converter for Mozilla Firefox browsersbull Converber [38] portable application converting utilitybull calculla [39] calculla - online web convertersbull iMetrix [40] - unit converter for xpbull uniteasy [41] online scientific unit conversionbull Unit Converter Add-in for Excel [42] - allow a large selection of unit conversions within the Microsoft Excel
spread sheet programbull Unit Converter [43] simple and extensible unit converterbull Portable Unit Converter [44] including 4500 units 33 unit-categories and the possibility to create custom units
General commercial sources of convertersbull Advanced electronic calculators have unit-conversion functionalitybull Spreadsheet programs usually provide conversion functions or formulas or the user can write their ownbull Commercial mathematical scientific and technical applications often include converters
See also
bull Accuracy and precisionbull English unitsbull False precisionbull Imperial unitsbull International System of Unitsbull Mesures usuellesbull Metric system
bull Natural unitsbull Roundingbull Significant figuresbull Temperature conversionbull United States customary unitsbull Units conversion by factor-labelbull Units of measurement
External linksbull British law Units of measurement regulations 1995 [45]
bull ConvertBuster [46] Variety of conversion tools to convert easilybull How Many A dictionary of units of measurement [47]
bull NIST Fundamental physical constants mdash Non-SI units [48]PDF (357 KB)bull NIST Guide to SI Units [49] Many conversion factors listedbull Online Conversion Calculators [50] Very extensive list of conversions from-to equvalent unitsbull The Unified Code for Units of Measure [51]
bull Units Symbols and Conversions XML Dictionary [52]
bull Multilingual Online Conversion of Units [53]
bull Temperature Converter [54]
Conversion of units 28
References[1] United States Naval Observatory (2009) Selected Astronomical Constants 2009 (http asa usno navy mil SecK 2009
Astronomical_Constants_2009 txt) Accessed May 10 2009[2] NIST Reference on Constants Units and Uncertainty (http physics nist gov cgi-bin cuu Valuebohrrada0|search_for=Bohr+
radius)(2006) National Institute of Standards and Technology Retrieved February 22 2008[3] National Institute of Standards and Technology General Tables of Units of Measurement (http ts nist gov WeightsAndMeasures
Publications appxc cfm)[4] Lide D (Ed) (1990) Handbook of Chemistry and Physics (71st ed) Boca Raton FL CRC Press Section 1[5] National Bureau of Standards (June 30 1959) Refinement of values for the yard and the pound Federal Register viewed September 20
2006 at National Geodetic Survey web site (http www ngs noaa gov PUBS_LIB FedRegister FRdoc59-5442 pdf)[6] The International Astronomical Union and Astronomical Units (http www iau org public_press themes measuring )[7] Klein Herbert Arthur (1988) The Science of Measurement a Historical Survey Mineola NY Dover Publications 0-4862-5839-4[8] The International System of Units Section 21 (http www bipm org en si si_brochure chapter2 2-1 ) (8 ed) Bureau International des
Poids et Mesures 2006 retrieved August 26 2009[9] International System of Units (http www bipm org en si si_brochure chapter4 table8 html) 8th ed (2006) Bureau International des
Poids et Mesures Section 41 Table 8[10] P Kenneth Seidelmann Ed (1992) Explanatory Supplement to the Astronomical Almanac Sausalito CA University Science Books p 716
and sv parsec in Glossary[11] Whitelaw Ian (2007) A Measure of All Things The Story of Man and Measurement (http books google com
booksid=3zgGEWM5-iAC) New York Macmillan 0-312-37026-1 p 152[12] De Vinne Theodore Low (1900) The practice of typography a treatise on the processes of type-making the point system the names sizes
styles and prices of plain printing types (http books google com booksid=R4-DjphIpLMC) 2nd ed New York The Century Co p142ndash150
[13] Pasko Wesley Washington (1894) American dictionary of printing and bookmaking (http books google combooksid=Z_QUAAAAIAAJ) (1894) New York Howard Lockwood p 521
[14] Rowlett Russ (2005) How Many A Dictionary of Units of Measurement (http www unc edu ~rowlett units index html)[15] Thompson A and Taylor BN (2008) Guide for the Use of the International System of Units (SI) National Institute of Standards and
Technology Special Publication 811 p 57[16] US Code of Federal Regulations Title 21 Section 1019 Paragraph (b)(5)(viii) (http ecfr gpoaccess gov cgi t text text-idxc=ecframp
rgn=div8amp view=textamp node=212 0 1 1 2 1 1 6amp idno=21) retrieved August 29 2009[17] Barry N Taylor Ed NIST Special Publication 330 The International System of Units (SI) (http physics nist gov Pubs SP330 sp330
pdf) (2001 Edition) Washington US Government Printing Office 43The 12th Conference Generale des Poids et Mesures(CGPM)hellipdeclares that the word ldquolitrerdquo may be employed as a special name for the cubic decimetre
[18] CODATA Value atomic uint of mass (http physics nist gov cgi-bin cuu Valuettme|search_for=atomic+ unit+ of+ mass) (2006)National Institute of Standards and Technology Retrieved 16 September 2008
[19] The Swiss Federal Office for Metrology gives Zentner on a German language web page (http www metas ch de scales systemch html)and quintal on the English translation of that page (http www metas ch en scales systemch html) the unit is marked speacutecifiquementsuisse
[20] Pedersen O (1983) Glossary in Coyne G Hoskin M and Pedersen O Gregorian Reform of the Calendar Proceedings of the VaticanConference to Commemorate its 400th Anniversary Vatican Observatory Available from Astrophysics Data System
[21] Richards EG (1998) Mapping Time Oxford University Press pp 94ndash95 ISBN 0-19-850413-6[22] Steel Duncan (2000) Marking Time John Wiley amp Sons p 46 ISBN 0-471-29827-1[23] CODATA Value atomic unit of force (http physics nist gov cuu Constants ) (2006) National Institute of Standards and Technology
Retrieved September 14 2008[24] [[Comiteacute International des Poids et Mesures (http www bipm org en CIPM db 1946 2 )] Resolution 2] 1946 retrieved August 26
2009[25] Barry N Taylor (April 1995) Guide for the Use of the International System of Units (SI) (http physics nist gov cuu pdf sp811 pdf)
(NIST Special Publication 811) Washington DC US Government Printing Office pp 57ndash68[26] Barry N Taylor (April 1995) Guide for the Use of the International System of Units (SI) (NIST Special Publication 811) Washington DC
US Government Printing Office p 5[27] International System of Units (http www bipm org en si si_brochure chapter4 table7 html) 8th ed (2006) Bureau International des
Poids et Mesures Section 41 Table 7[28] The NIST Reference on Constants Units and Uncertainty (http physics nist gov cgi-bin cuu Valueauedm) 2006 retrieved August
26 2009[29] NIST Guide to SI Units Appendix B9 (http physics nist gov Pubs SP811 appenB9 html) retrieved August 27 2009[30] Standard for the Use of the International System of Units (SI) The Modern Metric System IEEEASTM SI 10-1997 (1997) New York and
West Conshohocken PA Institute of Electrical and Electronics Engineers and American Society for Testing and Materials Tables A1through A5
Conversion of units 29
[31] The NIST Reference on Constants Units and Uncertainty (http physics nist gov cuu Units candela html) retrieved August 28 2009[32] Ambler Thompson amp Barry N Taylor (2008) Guide for the Use of the International System of Units (SI) (http physics nist gov cuu
pdf sp811 pdf) Special Publication 811 Gaithersburg MD National Institute of Standards and Technology p 10[33] The International System of Units Section 222 Table 3 (http www bipm org en si si_brochure chapter2 2-2 table3 html) (8 ed)
Bureau International des Poids et Mesures 2006 retrieved August 27 2009[34] The NIST Guide to the SI (Special Publication 811) section 52 (http physics nist gov Pubs SP811 sec05 html5 2) 2008 retrieved
August 27 2009[35] Ambler Thompson amp Barry N Taylor (2008) Guide for the Use of the International System of Units (SI) (http physics nist gov cuu
pdf sp811 pdf) Special Publication 811 Gaithersburg MD National Institute of Standards and Technology p 5[36] [[Comiteacute international des poids et mesures (http www bipm org en CIPM db 2002 2 )] 2002 Recommendation 2] retrieved
August 27 2009[37] http converter mozdev org[38] http www xyntec com converber htm[39] http www calculla com[40] http illusions hu index phptask=100amp lang=0amp statpage=86[41] http www uniteasy com[42] http www tenderwire com wikipedialandingpage[43] http www kamlex com index phpoption=com_contentamp view=articleamp id=53amp Itemid=55[44] http www sttmedia com unitconverter[45] http www hmso gov uk si si1995 Uksi_19951804_en_2 htm[46] http www convertbuster com[47] http www unc edu ~rowlett units[48] http physics nist gov cuu Document nonsi_in_1998 pdf[49] http physics nist gov Pubs SP811 appenB9 html[50] http www onlineconversion com[51] http aurora rg iupui edu ~schadow units UCUM ucum html[52] http www posc org refs poscUnits20 xml[53] http www imperialtometric com[54] http www tampile com
Article Sources and Contributors 30
Article Sources and ContributorsConversion of units Source httpenwikipediaorgwindexphpoldid=373975089 Contributors 1571781xxx 7 A-giau AVSI Acather96 Ahoerstemeier Alexius08 Altenmann AndreEngels Andrewa Andy120290 Anonymi Ariconte Army1987 ArnoldReinhold Arthur3030 Aspects AxelBoldt AzaToth Azikala BW95 Bdesham Beland Bensaccount Bkumartvm Blackand White BlaiseFEgan BlueEarth Bobblewik Borbrav Bpmullins Bryan Derksen C J B Scholten CORNELIUSSEON CTZMSC3 Calltech Camerajohn Chaosfeary Charles MatthewsChris the speller Cmdrjameson Colonies Chris Conversion script Cope555 Crappy13 Crissov CyrilB DARTH SIDIOUS 2 DMacks DanielCD Dark Formal DarkestSideX DekisugiDenelson83 Dhp1080 Dicklyon DirkvdM Donald Duck Donarreiskoffer Dramatic Dyss DAringsbquougosz Egil Ehrenkater Ejohnsonboulder Elexmax Elf Emokhberi Enon Eob Epbr123Euchiasmus Fathead99 Father Goose Fella22 Femto FernandoAC Fibula Flutefreek Fred Bauder Fredrik Fuhghettaboutit Fuzheado Gaff Gene Nygaard Georgiy1996 Gerry AshtonGiftlite Gilliam Glenn L GoingBatty Goobergunch Gregsexton Greyengine5 Grunt Gurch Gutza HLHJ Haemo Hammersbach Heracles31 Herbee Heron HikerBush Hqb IcairnsIgiffin Indefatigable Isis JBobbitt JHunterJ Jabowery JakeVortex Jamicanmonkey Jason Begin Jay Jc3s5h Jcronen1 Jdoherty Jeffz1 Jeronimo Jimmuhk Jimp Jimwilliams57 JoeinwapJohndburger Josh Parris Jq4bagiq Kaihsu KaneWang Keenan Pepper Kevin Rector KeyStorm Khukri Kurtan Lee Daniel Crocker LightYear Linuxoidoz Liv4christ210 Loggie Lolo252Lupinelawyer M ichaeligl MJCdetroit MTC Mac MacMcF Magore Markus Kuhn Masterqwe MaxHund Maxamegalon2000 Mbeychok Meggar Mh26 Michael Daly Michael Hardy MichelAudy Mikelifeguard Mikhailov Kusserow Mindbuilder Missvain Monger Mr bulow MrOllie MrZhuKeeper Muro de Aguas Mwanner Mwtoews Nandesuka Natkeeran Ndsg NgjaimeNhy67ygv Nick Y Nick123 NickPenguin Ninjagecko Noe Nosilleg Now3r3 Obelix homologator Oldadamml Oleg Alexandrov Olivier Ortolan88 OwenBlacker Pac72 PassargeaPatrick Paul Martin Peter Horn Physchim62 Piels Pierdm Pmanderson Prometheus235 Quadell QuantumEleven Quod erat demonstrandum 314159 Radagast83 Rccoms RedWolfReinyday Revipm Rexparry sydney Reyk Rhetth Rhialto Rich Farmbrough Richard Myers Rjwilmsi Rlsheehan Robin Barry RoySmith Rpwolfgram SD6-Agent SGBailey SamuelLowry Samw Sander123 Seabhcan SebastianHelm Sherbert1 Shinhan Shrew Sietse Snel SimonP Sinbaddasail0r Skotte Smalljim SomeHuman Spencer Srleffler StarwarsmastergeekSteacoon StefanK SteveRamone Stevertigo Stokerm Suisui Sunev Superboy112233 Superm401 Synchronism Tacoman1996 Tarquin Taw Teratornis The Man in Question ThierrycThingg Thinking of England Thunderbird2 Timwi Tobias Hoevekamp Tomasr Tonsofpcs Toon05 Topsykretts2512 Trekphiler Tuwile Twanvl Uday147502 Unitman00 UrhixidurUtherSRG Vargenau Vsmith WarrenPlatts Wasell Welsh Whispering Wikinger Wolfkeeper Wtmitchell XJamRastafire Xenonice Yath Zginder Zibem Zocky Zotel 713 anonymousedits
References[1] United States Naval Observatory (2009) Selected Astronomical Constants 2009 (http asa usno navy mil SecK 2009
Astronomical_Constants_2009 txt) Accessed May 10 2009[2] NIST Reference on Constants Units and Uncertainty (http physics nist gov cgi-bin cuu Valuebohrrada0|search_for=Bohr+
radius)(2006) National Institute of Standards and Technology Retrieved February 22 2008[3] National Institute of Standards and Technology General Tables of Units of Measurement (http ts nist gov WeightsAndMeasures
Publications appxc cfm)[4] Lide D (Ed) (1990) Handbook of Chemistry and Physics (71st ed) Boca Raton FL CRC Press Section 1[5] National Bureau of Standards (June 30 1959) Refinement of values for the yard and the pound Federal Register viewed September 20
2006 at National Geodetic Survey web site (http www ngs noaa gov PUBS_LIB FedRegister FRdoc59-5442 pdf)[6] The International Astronomical Union and Astronomical Units (http www iau org public_press themes measuring )[7] Klein Herbert Arthur (1988) The Science of Measurement a Historical Survey Mineola NY Dover Publications 0-4862-5839-4[8] The International System of Units Section 21 (http www bipm org en si si_brochure chapter2 2-1 ) (8 ed) Bureau International des
Poids et Mesures 2006 retrieved August 26 2009[9] International System of Units (http www bipm org en si si_brochure chapter4 table8 html) 8th ed (2006) Bureau International des
Poids et Mesures Section 41 Table 8[10] P Kenneth Seidelmann Ed (1992) Explanatory Supplement to the Astronomical Almanac Sausalito CA University Science Books p 716
and sv parsec in Glossary[11] Whitelaw Ian (2007) A Measure of All Things The Story of Man and Measurement (http books google com
booksid=3zgGEWM5-iAC) New York Macmillan 0-312-37026-1 p 152[12] De Vinne Theodore Low (1900) The practice of typography a treatise on the processes of type-making the point system the names sizes
styles and prices of plain printing types (http books google com booksid=R4-DjphIpLMC) 2nd ed New York The Century Co p142ndash150
[13] Pasko Wesley Washington (1894) American dictionary of printing and bookmaking (http books google combooksid=Z_QUAAAAIAAJ) (1894) New York Howard Lockwood p 521
[14] Rowlett Russ (2005) How Many A Dictionary of Units of Measurement (http www unc edu ~rowlett units index html)[15] Thompson A and Taylor BN (2008) Guide for the Use of the International System of Units (SI) National Institute of Standards and
Technology Special Publication 811 p 57[16] US Code of Federal Regulations Title 21 Section 1019 Paragraph (b)(5)(viii) (http ecfr gpoaccess gov cgi t text text-idxc=ecframp
rgn=div8amp view=textamp node=212 0 1 1 2 1 1 6amp idno=21) retrieved August 29 2009[17] Barry N Taylor Ed NIST Special Publication 330 The International System of Units (SI) (http physics nist gov Pubs SP330 sp330
pdf) (2001 Edition) Washington US Government Printing Office 43The 12th Conference Generale des Poids et Mesures(CGPM)hellipdeclares that the word ldquolitrerdquo may be employed as a special name for the cubic decimetre
[18] CODATA Value atomic uint of mass (http physics nist gov cgi-bin cuu Valuettme|search_for=atomic+ unit+ of+ mass) (2006)National Institute of Standards and Technology Retrieved 16 September 2008
[19] The Swiss Federal Office for Metrology gives Zentner on a German language web page (http www metas ch de scales systemch html)and quintal on the English translation of that page (http www metas ch en scales systemch html) the unit is marked speacutecifiquementsuisse
[20] Pedersen O (1983) Glossary in Coyne G Hoskin M and Pedersen O Gregorian Reform of the Calendar Proceedings of the VaticanConference to Commemorate its 400th Anniversary Vatican Observatory Available from Astrophysics Data System
[21] Richards EG (1998) Mapping Time Oxford University Press pp 94ndash95 ISBN 0-19-850413-6[22] Steel Duncan (2000) Marking Time John Wiley amp Sons p 46 ISBN 0-471-29827-1[23] CODATA Value atomic unit of force (http physics nist gov cuu Constants ) (2006) National Institute of Standards and Technology
Retrieved September 14 2008[24] [[Comiteacute International des Poids et Mesures (http www bipm org en CIPM db 1946 2 )] Resolution 2] 1946 retrieved August 26
2009[25] Barry N Taylor (April 1995) Guide for the Use of the International System of Units (SI) (http physics nist gov cuu pdf sp811 pdf)
(NIST Special Publication 811) Washington DC US Government Printing Office pp 57ndash68[26] Barry N Taylor (April 1995) Guide for the Use of the International System of Units (SI) (NIST Special Publication 811) Washington DC
US Government Printing Office p 5[27] International System of Units (http www bipm org en si si_brochure chapter4 table7 html) 8th ed (2006) Bureau International des
Poids et Mesures Section 41 Table 7[28] The NIST Reference on Constants Units and Uncertainty (http physics nist gov cgi-bin cuu Valueauedm) 2006 retrieved August
26 2009[29] NIST Guide to SI Units Appendix B9 (http physics nist gov Pubs SP811 appenB9 html) retrieved August 27 2009[30] Standard for the Use of the International System of Units (SI) The Modern Metric System IEEEASTM SI 10-1997 (1997) New York and
West Conshohocken PA Institute of Electrical and Electronics Engineers and American Society for Testing and Materials Tables A1through A5
Conversion of units 29
[31] The NIST Reference on Constants Units and Uncertainty (http physics nist gov cuu Units candela html) retrieved August 28 2009[32] Ambler Thompson amp Barry N Taylor (2008) Guide for the Use of the International System of Units (SI) (http physics nist gov cuu
pdf sp811 pdf) Special Publication 811 Gaithersburg MD National Institute of Standards and Technology p 10[33] The International System of Units Section 222 Table 3 (http www bipm org en si si_brochure chapter2 2-2 table3 html) (8 ed)
Bureau International des Poids et Mesures 2006 retrieved August 27 2009[34] The NIST Guide to the SI (Special Publication 811) section 52 (http physics nist gov Pubs SP811 sec05 html5 2) 2008 retrieved
August 27 2009[35] Ambler Thompson amp Barry N Taylor (2008) Guide for the Use of the International System of Units (SI) (http physics nist gov cuu
pdf sp811 pdf) Special Publication 811 Gaithersburg MD National Institute of Standards and Technology p 5[36] [[Comiteacute international des poids et mesures (http www bipm org en CIPM db 2002 2 )] 2002 Recommendation 2] retrieved
August 27 2009[37] http converter mozdev org[38] http www xyntec com converber htm[39] http www calculla com[40] http illusions hu index phptask=100amp lang=0amp statpage=86[41] http www uniteasy com[42] http www tenderwire com wikipedialandingpage[43] http www kamlex com index phpoption=com_contentamp view=articleamp id=53amp Itemid=55[44] http www sttmedia com unitconverter[45] http www hmso gov uk si si1995 Uksi_19951804_en_2 htm[46] http www convertbuster com[47] http www unc edu ~rowlett units[48] http physics nist gov cuu Document nonsi_in_1998 pdf[49] http physics nist gov Pubs SP811 appenB9 html[50] http www onlineconversion com[51] http aurora rg iupui edu ~schadow units UCUM ucum html[52] http www posc org refs poscUnits20 xml[53] http www imperialtometric com[54] http www tampile com
Article Sources and Contributors 30
Article Sources and ContributorsConversion of units Source httpenwikipediaorgwindexphpoldid=373975089 Contributors 1571781xxx 7 A-giau AVSI Acather96 Ahoerstemeier Alexius08 Altenmann AndreEngels Andrewa Andy120290 Anonymi Ariconte Army1987 ArnoldReinhold Arthur3030 Aspects AxelBoldt AzaToth Azikala BW95 Bdesham Beland Bensaccount Bkumartvm Blackand White BlaiseFEgan BlueEarth Bobblewik Borbrav Bpmullins Bryan Derksen C J B Scholten CORNELIUSSEON CTZMSC3 Calltech Camerajohn Chaosfeary Charles MatthewsChris the speller Cmdrjameson Colonies Chris Conversion script Cope555 Crappy13 Crissov CyrilB DARTH SIDIOUS 2 DMacks DanielCD Dark Formal DarkestSideX DekisugiDenelson83 Dhp1080 Dicklyon DirkvdM Donald Duck Donarreiskoffer Dramatic Dyss DAringsbquougosz Egil Ehrenkater Ejohnsonboulder Elexmax Elf Emokhberi Enon Eob Epbr123Euchiasmus Fathead99 Father Goose Fella22 Femto FernandoAC Fibula Flutefreek Fred Bauder Fredrik Fuhghettaboutit Fuzheado Gaff Gene Nygaard Georgiy1996 Gerry AshtonGiftlite Gilliam Glenn L GoingBatty Goobergunch Gregsexton Greyengine5 Grunt Gurch Gutza HLHJ Haemo Hammersbach Heracles31 Herbee Heron HikerBush Hqb IcairnsIgiffin Indefatigable Isis JBobbitt JHunterJ Jabowery JakeVortex Jamicanmonkey Jason Begin Jay Jc3s5h Jcronen1 Jdoherty Jeffz1 Jeronimo Jimmuhk Jimp Jimwilliams57 JoeinwapJohndburger Josh Parris Jq4bagiq Kaihsu KaneWang Keenan Pepper Kevin Rector KeyStorm Khukri Kurtan Lee Daniel Crocker LightYear Linuxoidoz Liv4christ210 Loggie Lolo252Lupinelawyer M ichaeligl MJCdetroit MTC Mac MacMcF Magore Markus Kuhn Masterqwe MaxHund Maxamegalon2000 Mbeychok Meggar Mh26 Michael Daly Michael Hardy MichelAudy Mikelifeguard Mikhailov Kusserow Mindbuilder Missvain Monger Mr bulow MrOllie MrZhuKeeper Muro de Aguas Mwanner Mwtoews Nandesuka Natkeeran Ndsg NgjaimeNhy67ygv Nick Y Nick123 NickPenguin Ninjagecko Noe Nosilleg Now3r3 Obelix homologator Oldadamml Oleg Alexandrov Olivier Ortolan88 OwenBlacker Pac72 PassargeaPatrick Paul Martin Peter Horn Physchim62 Piels Pierdm Pmanderson Prometheus235 Quadell QuantumEleven Quod erat demonstrandum 314159 Radagast83 Rccoms RedWolfReinyday Revipm Rexparry sydney Reyk Rhetth Rhialto Rich Farmbrough Richard Myers Rjwilmsi Rlsheehan Robin Barry RoySmith Rpwolfgram SD6-Agent SGBailey SamuelLowry Samw Sander123 Seabhcan SebastianHelm Sherbert1 Shinhan Shrew Sietse Snel SimonP Sinbaddasail0r Skotte Smalljim SomeHuman Spencer Srleffler StarwarsmastergeekSteacoon StefanK SteveRamone Stevertigo Stokerm Suisui Sunev Superboy112233 Superm401 Synchronism Tacoman1996 Tarquin Taw Teratornis The Man in Question ThierrycThingg Thinking of England Thunderbird2 Timwi Tobias Hoevekamp Tomasr Tonsofpcs Toon05 Topsykretts2512 Trekphiler Tuwile Twanvl Uday147502 Unitman00 UrhixidurUtherSRG Vargenau Vsmith WarrenPlatts Wasell Welsh Whispering Wikinger Wolfkeeper Wtmitchell XJamRastafire Xenonice Yath Zginder Zibem Zocky Zotel 713 anonymousedits
[31] The NIST Reference on Constants Units and Uncertainty (http physics nist gov cuu Units candela html) retrieved August 28 2009[32] Ambler Thompson amp Barry N Taylor (2008) Guide for the Use of the International System of Units (SI) (http physics nist gov cuu
pdf sp811 pdf) Special Publication 811 Gaithersburg MD National Institute of Standards and Technology p 10[33] The International System of Units Section 222 Table 3 (http www bipm org en si si_brochure chapter2 2-2 table3 html) (8 ed)
Bureau International des Poids et Mesures 2006 retrieved August 27 2009[34] The NIST Guide to the SI (Special Publication 811) section 52 (http physics nist gov Pubs SP811 sec05 html5 2) 2008 retrieved
August 27 2009[35] Ambler Thompson amp Barry N Taylor (2008) Guide for the Use of the International System of Units (SI) (http physics nist gov cuu
pdf sp811 pdf) Special Publication 811 Gaithersburg MD National Institute of Standards and Technology p 5[36] [[Comiteacute international des poids et mesures (http www bipm org en CIPM db 2002 2 )] 2002 Recommendation 2] retrieved
August 27 2009[37] http converter mozdev org[38] http www xyntec com converber htm[39] http www calculla com[40] http illusions hu index phptask=100amp lang=0amp statpage=86[41] http www uniteasy com[42] http www tenderwire com wikipedialandingpage[43] http www kamlex com index phpoption=com_contentamp view=articleamp id=53amp Itemid=55[44] http www sttmedia com unitconverter[45] http www hmso gov uk si si1995 Uksi_19951804_en_2 htm[46] http www convertbuster com[47] http www unc edu ~rowlett units[48] http physics nist gov cuu Document nonsi_in_1998 pdf[49] http physics nist gov Pubs SP811 appenB9 html[50] http www onlineconversion com[51] http aurora rg iupui edu ~schadow units UCUM ucum html[52] http www posc org refs poscUnits20 xml[53] http www imperialtometric com[54] http www tampile com
Article Sources and Contributors 30
Article Sources and ContributorsConversion of units Source httpenwikipediaorgwindexphpoldid=373975089 Contributors 1571781xxx 7 A-giau AVSI Acather96 Ahoerstemeier Alexius08 Altenmann AndreEngels Andrewa Andy120290 Anonymi Ariconte Army1987 ArnoldReinhold Arthur3030 Aspects AxelBoldt AzaToth Azikala BW95 Bdesham Beland Bensaccount Bkumartvm Blackand White BlaiseFEgan BlueEarth Bobblewik Borbrav Bpmullins Bryan Derksen C J B Scholten CORNELIUSSEON CTZMSC3 Calltech Camerajohn Chaosfeary Charles MatthewsChris the speller Cmdrjameson Colonies Chris Conversion script Cope555 Crappy13 Crissov CyrilB DARTH SIDIOUS 2 DMacks DanielCD Dark Formal DarkestSideX DekisugiDenelson83 Dhp1080 Dicklyon DirkvdM Donald Duck Donarreiskoffer Dramatic Dyss DAringsbquougosz Egil Ehrenkater Ejohnsonboulder Elexmax Elf Emokhberi Enon Eob Epbr123Euchiasmus Fathead99 Father Goose Fella22 Femto FernandoAC Fibula Flutefreek Fred Bauder Fredrik Fuhghettaboutit Fuzheado Gaff Gene Nygaard Georgiy1996 Gerry AshtonGiftlite Gilliam Glenn L GoingBatty Goobergunch Gregsexton Greyengine5 Grunt Gurch Gutza HLHJ Haemo Hammersbach Heracles31 Herbee Heron HikerBush Hqb IcairnsIgiffin Indefatigable Isis JBobbitt JHunterJ Jabowery JakeVortex Jamicanmonkey Jason Begin Jay Jc3s5h Jcronen1 Jdoherty Jeffz1 Jeronimo Jimmuhk Jimp Jimwilliams57 JoeinwapJohndburger Josh Parris Jq4bagiq Kaihsu KaneWang Keenan Pepper Kevin Rector KeyStorm Khukri Kurtan Lee Daniel Crocker LightYear Linuxoidoz Liv4christ210 Loggie Lolo252Lupinelawyer M ichaeligl MJCdetroit MTC Mac MacMcF Magore Markus Kuhn Masterqwe MaxHund Maxamegalon2000 Mbeychok Meggar Mh26 Michael Daly Michael Hardy MichelAudy Mikelifeguard Mikhailov Kusserow Mindbuilder Missvain Monger Mr bulow MrOllie MrZhuKeeper Muro de Aguas Mwanner Mwtoews Nandesuka Natkeeran Ndsg NgjaimeNhy67ygv Nick Y Nick123 NickPenguin Ninjagecko Noe Nosilleg Now3r3 Obelix homologator Oldadamml Oleg Alexandrov Olivier Ortolan88 OwenBlacker Pac72 PassargeaPatrick Paul Martin Peter Horn Physchim62 Piels Pierdm Pmanderson Prometheus235 Quadell QuantumEleven Quod erat demonstrandum 314159 Radagast83 Rccoms RedWolfReinyday Revipm Rexparry sydney Reyk Rhetth Rhialto Rich Farmbrough Richard Myers Rjwilmsi Rlsheehan Robin Barry RoySmith Rpwolfgram SD6-Agent SGBailey SamuelLowry Samw Sander123 Seabhcan SebastianHelm Sherbert1 Shinhan Shrew Sietse Snel SimonP Sinbaddasail0r Skotte Smalljim SomeHuman Spencer Srleffler StarwarsmastergeekSteacoon StefanK SteveRamone Stevertigo Stokerm Suisui Sunev Superboy112233 Superm401 Synchronism Tacoman1996 Tarquin Taw Teratornis The Man in Question ThierrycThingg Thinking of England Thunderbird2 Timwi Tobias Hoevekamp Tomasr Tonsofpcs Toon05 Topsykretts2512 Trekphiler Tuwile Twanvl Uday147502 Unitman00 UrhixidurUtherSRG Vargenau Vsmith WarrenPlatts Wasell Welsh Whispering Wikinger Wolfkeeper Wtmitchell XJamRastafire Xenonice Yath Zginder Zibem Zocky Zotel 713 anonymousedits