Measurement (LINEAR) – CONVERSION

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Conversion of units is the conversion between different units of measurement for the same quantity, typically through multiplicative conversion factors.

Techniques

Process overview

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.
  • Historical definitions of the units and their derivatives used in old measurements; e.g., international foot vs. US survey foot.

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. Nominal values are sometimes allowed and used.

Conversion factors

A conversion factor is used to change the units of a measured quantity without changing its value. The unity bracket method of unit conversion consists of a fraction in which the denominator is equal to the numerator, but they are in different units. Because of the identity property of multiplication, the value of a quantity will not change as long as it is multiplied by one. Also, if the numerator and denominator of a fraction are equal to each other, then the fraction is equal to one. So as long as the numerator and denominator of the fraction are equivalent, they will not affect the value of the measured quantity.

The following example demonstrates how the unity bracket method is used to convert the rate 5 kilometers per second to meters per second. The symbols km, m, and s represent kilometer, meter, and second, respectively.

Thus, it is found that 5 kilometers per second is equal to 5000 meters per second.

Software tools

There are many conversion tools. They are found in the function libraries of applications such as spreadsheets databases, in calculators, and in macro packages and plugins for many other applications such as the mathematical, scientific and technical applications.

There are many standalone applications that offer the thousands of the various units with conversions. For example, the free software movement offers a command line utility GNU units for Linux and Windows.

Calculation involving non-SI Units

In the cases where non-SI units are used, the numerical calculation of a formula can be done by first working out the pre-factor, and then plug in the numerical values of the given/known quantities.

For example, in the study of Bose–Einstein condensate, atomic mass m is usually given in daltons, instead of kilograms, and chemical potential μ is often given in Boltzmann constant times nanokelvin. The condensate's healing length is given by:

For a 23Na condensate with chemical potential of (Boltzmann constant times) 128 nK, the calculation of healing length (in micrometres) can be done in two steps:

Calculate the pre-factor

Assume that this gives

which is our pre-factor.

Calculate the numbers

Now, make use of the fact that . With , .

This method is especially useful for programming and/or making a worksheet, where input quantities are taking multiple different values; For example, with the pre-factor calculated above, it's very easy to see that the healing length of 174Yb with chemical potential 20.3 nK is .

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. Conversions between units in the metric system are defined 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). Within each table, the units are listed alphabetically, and the SI units (base or derived) are highlighted.

Legend
Symbol Definition
exactly equal
approximately equal to
(exactly) corresponds to (different types of quantity describing the same phenomenon)
Template:Overline indicates that digits repeat infinitely (e.g. Template:Gaps corresponds to Template:Gaps)
(H) of chiefly historical interest

Length

Length
Name of unit Symbol Definition Relation to SI units
ångström Å Template:Val ≡ 0.1 nm
astronomical unit au Template:Val
≈ Distance from Earth to Sun
Template:Val [1]
attometre am Template:Val Template:Val
barleycorn (H)   = Template:Frac in (see note above about rounding) = 8.4Template:OverlineTemplate:E m
bohr, atomic unit of length a0 = Bohr radius of hydrogen Template:Val[2]
cable length (imperial)   ≡ 608 ft ≈ 185.3184 m
cable length (International)   Template:Frac nmi ≡ 185.2 m
cable length (US)   ≡ 720 ft = 219.456 m
chain (Gunter's; Surveyor's) ch ≡ 66 ft (US) ≡ 4 rods[3] Template:Val
cubit (H)   ≡ Distance from fingers to elbow ≈ 18 in ≈ 0.5 m
ell (H) ell ≡ 45 in [4] (In England usually) = 1.143 m
fathom ftm ≡ 6 ft [4] = 1.8288 m
femtometre fm Template:Val Template:Val
fermi fm Template:Val[4] Template:Val
finger   Template:Frac in = Template:Val
finger (cloth)   Template:Frac in = 0.1143 m
foot (Benoît) (H) ft (Ben) Template:Val
foot (Cape) (H)   Legally defined as 1.033 English feet in 1859 Template:Val
foot (Clarke's) (H) ft (Cla) Template:Val
foot (Indian) (H) ft Ind Template:Val
foot, metric mf ≡ 300 mm ≡ 0.3 m
foot, metric (Mesures usuelles) (H) Template:Frac m ≡ 0.Template:Overline m
foot (International) ft ≡ 0.3048 m ≡ Template:Frac yd ≡ 12 inches ≡ 0.3048 m
foot (Sear's) (H) ft (Sear) Template:Val
foot (US Survey) ft (US) Template:Frac m [5] Template:Val
french; charriere F Template:Frac mm = 0.Template:Overline Template:E m
furlong fur ≡ 10 chains = 660 ft = 220 yd [4] = 201.168 m
hand   ≡ 4 in [4] ≡ 0.1016 m
inch (International) in ≡ 2.54 cm ≡ Template:Frac yd ≡ Template:Frac ft ≡ 0.0254 m
league (land) lea ≈ 1 hour walk, Currently defined in US as 3 Statute miles,[3] but historically varied from 2 to 9 km Template:Val
light-day   ≡ 24 light-hours Template:Val
light-hour   ≡ 60 light-minutes Template:Val
light-minute   ≡ 60 light-seconds Template:Val
light-second   ≡ Distance light travels in one second in vacuum Template:Val
light-year ly ≡ Distance light travels in vacuum in 365.25 days [6] Template:Val
line ln Template:Frac in [7] = Template:Gaps m
link (Gunter's; Surveyor's) lnk Template:Frac ch [4] ≡ 0.66 ft (US) ≡ 7.92 in Template:Val
link (Ramsden's; Engineer's) lnk ≡ 1 ft [4] = 0.3048 m
metre (SI base unit)
(meter)
m ≡ Distance light travels in Template:Frac of a second in vacuum.[8] (SI base unit)
mickey   Template:Frac in = Template:Val
micrometre (old: micron) μ; μm Template:Val Template:Val
mil; thou mil Template:Val = Template:Val
mil (Sweden and Norway) mil ≡ 10 km = Template:Val
mile (geographical) (H) Template:Val = Template:Val
mile (international) mi ≡ 80 chains ≡ Template:ValTemplate:Val Template:Val
mile (tactical or data) Template:Val Template:Val
mile (telegraph) (H) mi Template:Val = Template:Val
mile (US Survey) mi Template:Val US Survey feet ≡ (Template:Val × Template:Frac) m Template:Val
nail (cloth)   Template:Frac in [4] = Template:Val
nanometre nm Template:Val Template:Val
nautical league NL; nl ≡ 3 nmi [4] = Template:Val
nautical mile (Admiralty) NM (Adm); nmi (Adm) = Template:Val = Template:Val
nautical mile (international) NM; nmi Template:Val[9] Template:Val
nautical mile (US pre 1954) ≡ 1853.248 m ≡ 1853.248 m
pace   ≡ 2.5 ft [4] = 0.762 m
palm   ≡ 3 in [4] = 0.0762 m
parsec pc Distant point with a parallax shift of one arc second from a base of one astronomical unit.
Template:Sfrac au[10][11]
Template:Val[12]
pica   ≡ 12 points Dependent on point measures.
picometre pm Template:Val Template:Val
point (American, English)[13][14] pt Template:Frac in Template:Val
point (Didot; European) [14][15] pt Template:Frac × Template:Frac of pied du roi;

After 1878:
Template:Frac cm
Template:Val;

After 1878:
Template:Val
point (PostScript) [13] pt Template:Frac in = Template:Gaps m
point (TeX) [13] pt Template:Frac in = 0.00Template:Overline m
quarter   Template:Frac yd = 0.2286 m
rod; pole; perch (H) rd Template:Frac ft = 5.0292 m
rope (H) rope ≡ 20 ft [4] = 6.096 m
shaku (Japan) ≡ 10/33 m ≈ 0.303 0303 m
span (H)   ≡ 9 in [4] = 0.2286 m
spat[16] Template:Val
stick (H)   ≡ 2 in = 0.0508 m
toise (French, post 1667) (H) T ≡ 27000/13853 m ≈ 1.949 0363 m
twip twp Template:Frac in = 1.763Template:OverlineTemplate:E m
x unit; siegbahn xu Template:Val m [4]
yard (International) yd ≡ 0.9144 m [5] ≡ 3 ft ≡ 36 in ≡ 0.9144 m
yoctometre ym Template:Val Template:Val
zeptometre zm Template:Val Template:Val

Area

Area
Name of unit Symbol Definition Relation to SI units
acre (international) ac Template:Nowrap = Template:Val Template:Val
acre (US survey) ac ≡ 10 sq ch = Template:Val, also Template:Val Template:Val[17]
are a ≡ 100 m2 ≡ 100 m2
barn b ≡ 10−28 m2 ≡ 10−28 m2
barony   Template:Val ac Template:Val
board bd Template:Nowrap Template:Val
boiler horsepower equivalent direct radiation bhp EDR ≡ 1 ft2 × 1 bhp / (240 BTUIT/h) Template:Val
circular inch circ in Template:Frac sq in Template:Val
circular mil; circular thou circ mil Template:Frac mil2 Template:Val
cord   ≡ 192 bd Template:Val
cuerda (PR Survey) cda ≡ 1 cda x 1 cda = Template:Val acre Template:Val
dunam   Template:Val Template:Val
guntha (India)   ≡ 121 sq yd ≈ 101.17 m2
hectare ha Template:Val Template:Val
hide   ≈ 120 ac (variable) Template:Val
rood ro Template:Frac ac = Template:Val
ping Template:Frac m × Template:Frac m Template:Val
section Template:Nowrap = Template:Val
shed   ≡ 10−52 m2 = 10−52 m2
square (roofing) Template:Nowrap = Template:Val
square chain (international) sq ch Template:Nowrap = Template:Frac ac Template:Val
square chain (US Survey) sq ch Template:Nowrap = Template:Frac US survey acre Template:Val
square foot sq ft Template:Nowrap Template:Val
square foot (US Survey) sq ft Template:Nowrap Template:Val
square inch sq in Template:Nowrap Template:Val
square kilometre km2 ≡ 1 km × 1 km = 106 m2
square link (Gunter's)(International) sq lnk ≡ 1 lnk × 1 lnk ≡ 0.66 ft × 0.66 ft = Template:Val
square link (Gunter's)(US Survey) sq lnk Template:NowrapTemplate:Nowrap Template:Val
square link (Ramsden's) sq lnk ≡ 1 lnk × 1 lnk ≡ 1 ft × 1 ft = Template:Val
square metre (SI unit) m2 ≡ 1 m × 1 m = 1 m2
square mil; square thou sq mil ≡ 1 mil × 1 mil = Template:Val
square mile sq mi ≡ 1 mi × 1 mi Template:Val
square mile (US Survey) sq mi ≡ 1 mi (US) × 1 mi (US) Template:Val
square rod/pole/perch sq rd ≡ 1 rd × 1 rd = Template:Val
square yard (International) sq yd ≡ 1 yd × 1 yd Template:Val
stremma   Template:Val = Template:Val
township   ≡ 36 sq mi (US) Template:Val
yardland   ≈ 30 ac Template:Val

Volume

Volume
Name of unit Symbol Definition Relation to SI units
acre-foot ac ft ≡ 1 ac x 1 ft = Template:Val = Template:Val
acre-inch   ≡ 1 ac × 1 in = Template:Val
barrel (imperial) bl (imp) ≡ 36 gal (imp) = Template:Val
barrel (petroleum); archaic blue-barrel bl; bbl ≡ 42 gal (US) = Template:Val
barrel (US dry) bl (US) ≡ 105 qt (US) = 105/32 bu (US lvl) = Template:Val
barrel (US fluid) fl bl (US) Template:Frac gal (US) = Template:Val
board-foot bdft ≡ 144 cu in Template:Val
bucket (imperial) bkt ≡ 4 gal (imp) = Template:Val
bushel (imperial) bu (imp) ≡ 8 gal (imp) = Template:Val
bushel (US dry heaped) bu (US) Template:Frac bu (US lvl) = Template:Val
bushel (US dry level) bu (US lvl) Template:Val = Template:Val
butt, pipe   ≡ 126 gal (US) (wine) = Template:Val
coomb   ≡ 4 bu (imp) = Template:Val
cord (firewood)   Template:Nowrap = Template:Val
cord-foot   ≡ 16 cu ft = Template:Val
cubic fathom cu fm ≡ 1 fm × 1 fm × 1 fm = Template:Val
cubic foot ft3 ≡ 1 ft × 1 ft × 1 ft Template:Val
cubic inch in3 ≡ 1 in × 1 in × 1 in Template:Val
cubic metre (SI unit) m3 ≡ 1 m × 1 m × 1 m ≡ 1 m3
cubic mile cu mi ≡ 1 mi × 1 mi × 1 mi Template:Val
cubic yard yd3 ≡ 27 cu ft Template:Val
cup (breakfast)   ≡ 10 fl oz (imp) = Template:Val
cup (Canadian) c (CA) ≡ 8 fl oz (imp) = Template:Val
cup (metric) c Template:Val Template:Val
cup (US customary) c (US) ≡ 8 US fl oz ≡ Template:Frac gal (US) = Template:Val
cup (US food nutrition labeling) c (US) ≡ 240 mL[18] = Template:Val
dash (imperial)   Template:Frac gi (imp) = Template:Frac pinch (imp) = Template:GapsTemplate:E m3
dash (US)   Template:Frac US fl oz = Template:Frac US pinch = Template:Val
dessertspoon (imperial)   Template:Frac gi (imp) = Template:GapsTemplate:E m3
drop (imperial) gtt Template:Frac fl oz (imp) = Template:GapsTemplate:E m3
drop (imperial) (alt) gtt Template:Frac gi (imp) Template:Val
drop (medical)   Template:Frac mL = 83.Template:OverlineTemplate:E m3
drop (metric)   Template:Frac mL = Template:Val
drop (US) gtt Template:Frac US fl oz = Template:GapsTemplate:E m3
drop (US) (alt) gtt Template:Frac US fl oz Template:Val
drop (US) (alt) gtt Template:Frac US fl oz Template:Val
fifth   Template:Frac US gal = Template:Val
firkin   ≡ 9 gal (imp) = Template:Val
fluid drachm (imperial) fl dr Template:Frac fl oz (imp) = Template:Val
fluid dram (US); US fluidram fl dr Template:Frac US fl oz = Template:Val
fluid scruple (imperial) fl s Template:Frac fl oz (imp) = Template:GapsTemplate:E m3
gallon (beer) beer gal ≡ 282 cu in = Template:Val
gallon (imperial) gal (imp) Template:Val Template:Val
gallon (US dry) gal (US) Template:Frac bu (US lvl) = Template:Val
gallon (US fluid; Wine) gal (US) ≡ 231 cu in Template:Val
gill (imperial); Noggin gi (imp); nog ≡ 5 fl oz (imp) = Template:Val
gill (US) gi (US) ≡ 4 US fl oz = Template:Val
hogshead (imperial) hhd (imp) ≡ 2 bl (imp) = Template:Val
hogshead (US) hhd (US) ≡ 2 fl bl (US) = Template:Val
jigger (bartending)   Template:Frac US fl oz Template:Val
kilderkin   ≡ 18 gal (imp) = Template:Val
lambda λ ≡ 1 mm3 = Template:Val
last   ≡ 80 bu (imp) = Template:Val
litre
(liter)
L or l ≡ 1 dm3 [19] ≡ 0.001 m3
load   ≡ 50 cu ft = Template:Val
minim (imperial) min Template:Frac fl oz (imp) = 1/60 fl dr (imp) = Template:GapsTemplate:E m3
minim (US) min Template:Frac US fl oz = Template:Frac US fl dr = Template:Val
ounce (fluid imperial) fl oz (imp) Template:Frac gal (imp) Template:Val
ounce (fluid US customary) US fl oz Template:Frac gal (US) Template:Val
ounce (fluid US food nutrition labeling) US fl oz ≡ 30 mL[18] Template:Val
peck (imperial) pk ≡ 2 gal (imp) = Template:Val
peck (US dry) pk Template:Frac US lvl bu = Template:Val
perch per Template:Nowrap = Template:Val
pinch (imperial)   Template:Frac gi (imp) = 1/16 tsp (imp) = Template:GapsTemplate:E m3
pinch (US)   Template:Frac US fl oz = 1/16 US tsp = Template:Val
pint (imperial) pt (imp) Template:Frac gal (imp) = Template:Val
pint (US dry) pt (US dry) Template:Frac bu (US lvl) ≡ Template:Frac gal (US dry) = Template:Val
pint (US fluid) pt (US fl) Template:Frac gal (US) = Template:Val
pony   Template:Frac US fl oz = Template:Val
pottle; quartern   Template:Frac gal (imp) = 80 fl oz (imp) = Template:Val
quart (imperial) qt (imp) Template:Frac gal (imp) = Template:Val
quart (US dry) qt (US) Template:Frac bu (US lvl) = Template:Frac gal (US dry) = Template:Val
quart (US fluid) qt (US) Template:Frac gal (US fl) = Template:Val
quarter; pail   ≡ 8 bu (imp) = Template:Val
register ton   ≡ 100 cu ft = Template:Val
sack (US)   ≡ 3 bu (US lvl) = Template:Val
seam   ≡ 8 bu [16] = Template:Val
shot (US)   usually 1.5 US fl oz[16] Template:Val
strike (imperial)   ≡ 2 bu (imp) = Template:Val
strike (US)   ≡ 2 bu (US lvl) = Template:Val
tablespoon (Australian metric)   Template:Val
tablespoon (Canadian) tbsp Template:Frac fl oz (imp) = Template:Val
tablespoon (imperial) tbsp Template:Frac fl oz (imp) = Template:Val
tablespoon (metric)   Template:Val
tablespoon (US customary) tbsp Template:Frac US fl oz = Template:Val
tablespoon (US food nutrition labeling) tbsp ≡ 15 mL[18] = Template:Val
teaspoon (Canadian) tsp Template:Frac fl oz (imp) = Template:GapsTemplate:E m3
teaspoon (imperial) tsp Template:Frac gi (imp) = Template:GapsTemplate:E m3
teaspoon (metric)   Template:Val Template:Val
teaspoon (US customary) tsp Template:Frac US fl oz = Template:Val
teaspoon (US food nutrition labeling) tsp ≡ 5 mL[18] = Template:Val
timber foot   ≡ 1 cu ft = Template:Val
ton (displacement)   ≡ 35 cu ft = Template:Val
ton (freight)   ≡ 40 cu ft = Template:Val
ton (water)   ≡ 28 bu (imp) = Template:Val
tun   ≡ 252 gal (wine) = Template:Val
wey (US)   ≡ 40 bu (US lvl) = Template:Val

Plane angle

Plane angle
Name of unit Symbol Definition Relation to SI units
NATO mil (various) Template:Frac rad Template:Val
Swedish streck Template:Frac rad Template:Val
milliradian mrad Template:Frac rad Template:Val
Warsaw Pact mil Template:Frac rad Template:Val
arcminute; MOA ' Template:Frac Template:Val
arcsecond " Template:Frac Template:Val
centesimal minute of arc ' Template:Frac grad Template:Val
centesimal second of arc " Template:Frac grad Template:Val
degree (of arc) ° Template:Frac of a revolution ≡ Template:Frac rad Template:Val
grad; gradian; gon grad Template:Frac of a revolution ≡ Template:Frac rad ≡ 0.9° Template:Nowrap
octant   ≡ 45° Template:Val
quadrant   ≡ 90° Template:Val
radian (SI unit) rad The angle subtended at the center of a circle by an arc whose length is equal to the circle's radius.
One full revolution encompasses 2π radians.
= 1 rad
sextant   ≡ 60° Template:Val
sign   ≡ 30° Template:Val

Solid angle

Solid angle
Name of unit Symbol Definition Relation to SI units
spat Template:Nowrap[16] – The solid angle subtended by a sphere at its centre. Template:Nowrap
square degree deg2; sq.deg.; (°)2 Template:Nowrap Template:Nowrap
steradian (SI unit) sr The solid angle subtended at the center of a sphere of radius r by a portion of the surface of the sphere having an area r2.
A sphere subtends 4π sr.[16]
= 1 sr

Mass

Notes:

  • See Weight for detail of mass/weight distinction and conversion.
  • Avoirdupois is a system of mass based on a pound of 16 ounces, while Troy weight is the system of mass where 12 troy ounces equals one troy pound.
  • In this table, the symbol g0 is used to denote standard gravity in order to avoid confusion with the (upright) g symbol for gram.
Mass
Name of unit Symbol Definition Relation to SI units
atomic mass unit, unified u; AMU Same as dalton (see below) Template:Val[3]
atomic unit of mass, electron rest mass me Template:Val[20]
bag (coffee)   ≡ 60 kg = 60 kg
bag (Portland cement)   ≡ 94 lb av = Template:Val
barge   Template:Frac short ton = Template:Val
carat kt Template:Frac gr = Template:ValTemplate:Overline mg
carat (metric) ct ≡ 200 mg = 200 mg
clove   ≡ 8 lb av = Template:Val
crith   ≡ mass of 1 L of hydrogen gas at STP ≈ 89.9349 mg
dalton Da 1/12 the mass of an unbound neutral atom of carbon-12 in its nuclear and electronic ground state and at rest Template:Val[3]
dram (apothecary; troy) dr t ≡ 60 gr = Template:Val
dram (avoirdupois) dr av Template:Frac gr = Template:Val
electronvolt eV ≡ 1 eV (energy unit) / c2 = Template:Val[3]
gamma γ ≡ 1 μg = 1 μg
grain gr Template:Frac lb av Template:Val
grave gv grave was the original name of the kilogram ≡ 1 kg
hundredweight (long) long cwt or cwt ≡ 112 lb av = Template:Val
hundredweight (short); cental sh cwt ≡ 100 lb av = Template:Val
kilogram
(kilogramme)
kg ≈ mass of the prototype near Paris
≈ mass of 1 litre of water
(SI base unit)[8]
kip kip Template:Val av = Template:Val
mark   ≡ 8 oz t = Template:Val
mite   Template:Frac gr = Template:Val
mite (metric)   Template:Frac g = 50 mg
ounce (apothecary; troy) oz t Template:Frac lb t = Template:Val
ounce (avoirdupois) oz av Template:Frac lb = Template:Val
ounce (US food nutrition labelling) oz ≡ 28 g[18] = 28 g
pennyweight dwt; pwt Template:Frac oz t = Template:Val
point   Template:Frac ct = 2 mg
pound (avoirdupois) lb av Template:Val = Template:Val grains Template:Val
pound (metric)   ≡ 500 g = 500 g
pound (troy) lb t Template:Val grains = Template:Val
quarter (imperial)   Template:Frac long cwt = 2 st = 28 lb av = Template:Val
quarter (informal)   Template:Frac short ton = Template:Val
quarter, long (informal)   Template:Frac long ton = Template:Val
quintal (metric) q ≡ 100 kg = 100 kg
scruple (apothecary) s ap ≡ 20 gr = Template:Val
sheet   Template:Frac lb av = 647.9891 mg
slug; geepound; hyl slug g0 × 1 lb av × 1 s2/ft Template:Val
stone st ≡ 14 lb av = Template:Val
ton, assay (long) AT ≡ 1 mg × 1 long ton ÷ 1 oz t = 32.Template:Overline g
ton, assay (short) AT ≡ 1 mg × 1 short ton ÷ 1 oz t = 29.1Template:Overline g
ton, long long tn or ton Template:Val = Template:Val
ton, short sh tn Template:Val = Template:Val
tonne (mts unit) t Template:Val = Template:Val
wey   ≡ 252 lb = 18 st = Template:Val (variants exist)
Zentner Ztr. Definitions vary.[16][21]

Density

Density
Name of unit Symbol Definition Relation to SI units
gram per millilitre g/mL ≡ g/mL = Template:Val
kilogram per cubic metre (SI unit) kg/m3 ≡ kg/m3 = 1 kg/m3
kilogram per litre kg/L ≡ kg/L = Template:Val
ounce (avoirdupois) per cubic foot oz/ft3 ≡ oz/ft3 Template:Val
ounce (avoirdupois) per cubic inch oz/in3 ≡ oz/in3 Template:Val
ounce (avoirdupois) per gallon (imperial) oz/gal ≡ oz/gal Template:Val
ounce (avoirdupois) per gallon (US fluid) oz/gal ≡ oz/gal Template:Val
pound (avoirdupois) per cubic foot lb/ft3 ≡ lb/ft3 Template:Val
pound (avoirdupois) per cubic inch lb/in3 ≡ lb/in3 Template:Val
pound (avoirdupois) per gallon (imperial) lb/gal ≡ lb/gal Template:Val
pound (avoirdupois) per gallon (US fluid) lb/gal ≡ lb/gal Template:Val
slug per cubic foot slug/ft3 ≡ slug/ft3 Template:Val

Time

Time
Name of unit Symbol Definition Relation to SI units
Atomic unit of time au a0/(αc) Template:Val
Callippic cycle   ≡ 441 mo (hollow) + 499 mo (full) = 76 a of 365.25 d = Template:Val or Template:Val[note 1]
Century c ≡ 100 years (100 a) Template:Val[note 2][note 3]
Day d = 24 h = Template:Val min = Template:Val[note 3]
Day (sidereal) d ≡ Time needed for the Earth to rotate once around its axis, determined from successive transits of a very distant astronomical object across an observer's meridian (International Celestial Reference Frame) Template:Val
Decade dec ≡ 10 years (10 a) = Template:Val[note 2][note 3]
Fortnight fn ≡ 2 wk = Template:Val[note 3]
Helek Template:Frac h = 3.Template:Overline s
Hipparchic cycle   ≡ 4 Callippic cycles - 1 d = Template:Val
Hour h ≡ 60 min = Template:Val[note 3]
Jiffy j Template:Frac s = 16.Template:Overline ms
Jiffy (alternative) ja Template:Frac s = 10 ms
Ke (quarter of an hour)   Template:Frac h = Template:Frac d = 15 min = 900 s
Ke (traditional)   Template:Frac d = 14.4 min = 864 s
Lustre; Lustrum   ≡ 5 a of 365 d[note 4] = Template:Val
Metonic cycle; enneadecaeteris   ≡ 110 mo (hollow) + 125 mo (full) = 6940 d ≈ 19 a = Template:Val
Millennium   Template:Val years (Template:Val) Template:Val[note 2][note 3]
Milliday md Template:Frac d = 86.4 s
Minute min ≡ 60 s, due to leap seconds sometimes 59 s or 61 s, = 60 s[note 3]
Moment   ≡ 90 s = 90 s
Month (full) mo ≡ 30 d[22] = Template:Val[note 3]
Month (Greg. av.) mo = Template:Val Template:Val[note 3]
Month (hollow) mo ≡ 29 d[22] = Template:Val[note 3]
Month (synodic) mo Cycle time of moon phases ≈ Template:Val (average) Template:Val
Octaeteris   = 48 mo (full) + 48 mo (hollow) + 3 mo (full)[23][24] = 8 a of 365.25 d = 2922 d = Template:Val[note 3]
Planck time   ≡ (Template:Frac)Template:Frac Template:Val[25]
Second (SI base unit) s ≡ Time of Template:Val periods of the radiation corresponding to the transition between the two hyperfine levels of the ground state of the caesium-133 atom at 0 K[8] (but other seconds are sometimes used in astronomy). Also that time it takes for light to travel a distance of Template:Val metres. (SI base unit)
Shake   ≡ 10−8 s = 10 ns
Sigma   ≡ 10−6 s = 1 μs
Sothic cycle   Template:Val a of 365 d = Template:Val
Svedberg S ≡ 10−13 s = 100 fs
Week wk ≡ 7 d = 168 h = Template:Val = Template:Val[note 3]
Year (common) Template:Nowrap 365 d = Template:Val[note 3][26]
Year (Gregorian) a, y, or yr = 365.2425 d average, calculated from common years (365 d) plus leap years (366 d) on most years divisible by 4. See leap year for details. = Template:Val[note 3]
Year (Julian) a, y, or yr = 365.25 d average, calculated from common years (365 d) plus one leap year (366 d) every four years = Template:Val
Year (leap) a, y, or yr 366 d = Template:Val[note 3][26]
Year (mean tropical) a, y, or yr Conceptually, the length of time it takes for the Sun to return to the same position in the cycle of seasons, [Converter 1] approximately Template:Val d, each day being Template:Val SI seconds[27] Template:Val
Year (sidereal) a, y, or yr ≡ Time taken for Sun to return to the same position with respect to the stars of the celestial sphere, approximately Template:Val Template:Val
Notes:
  1. see Callippic cycle for explanation of the differences
  2. 2.0 2.1 2.2 This is based on the average Gregorian year. See above for definition of year lengths.
  3. 3.00 3.01 3.02 3.03 3.04 3.05 3.06 3.07 3.08 3.09 3.10 3.11 3.12 3.13 3.14 Where UTC is observed, the length of this unit may increase or decrease
    depending on the number of leap seconds which occur during the time interval in question.
  4. The length of ancient lustral cycles was not constant; see Lustrum for more details

Frequency

Frequency
Name of unit Symbol Definition Relation to SI units
Actions per minute APM ≡ 1/60 Hz Template:Val
Cycle per second cps ≡ 1 Hz = 1 cps = 1 Hz
degree per second deg/s ≡ 1 °/s ≡ 1/360 Hz = Template:ValTemplate:Overline Hz
hertz (SI unit) Hz ≡ One cycle per second = 1 Hz = 1/s
Radian per second rad/s ≡ 1/(2π) Hz Template:Val
revolutions per minute rpm ≡ One unit rpm equals one rotation completed around a fixed axis in one minute of time. Template:Val

Speed or velocity

Speed
Name of unit Symbol Definition Relation to SI units
foot per hour fph ≡ 1 ft/h = 8.4Template:OverlineTemplate:E m/s
foot per minute fpm ≡ 1 ft/min = Template:Val
foot per second fps ≡ 1 ft/s = Template:Val
furlong per fortnight   ≡ furlong/fortnight Template:Val
inch per hour iph ≡ 1 in/h = 7.0Template:OverlineTemplate:E m/s
inch per minute ipm ≡ 1 in/min = 4.2Template:OverlineTemplate:E m/s
inch per second ips ≡ 1 in/s = Template:Val
kilometre per hour km/h ≡ 1 km/h = 2.Template:OverlineTemplate:E m/s
knot kn ≡ 1 nmi/h = 1.852 km/h = 0.51Template:Overline m/s
knot (Admiralty) kn ≡ 1 NM (Adm)/h = Template:Val[28] = Template:ValTemplate:Overline m/s
mach number M Ratio of the speed to the speed of sound[note 1] in the medium (unitless). ≈ 340 m/s in air at sea level
≈ 295 m/s in air at jet altitudes
metre per second (SI unit) m/s ≡ 1 m/s = 1 m/s
mile per hour mph ≡ 1 mi/h = Template:Val
mile per minute mpm ≡ 1 mi/min = Template:Val
mile per second mps ≡ 1 mi/s = Template:Val
speed of light in vacuum c Template:Val = Template:Val
speed of sound in air s Template:Val to Template:Val (Template:Convert)[note 1] Template:Val
Note
  1. 1.0 1.1 The speed of sound varies especially with temperature and pressure from about Template:Val (Template:Convert)
    in air at sea level to about Template:Val (Template:Convert) at jet altitudes (Template:Convert).[29]

A velocity consists of a speed combined with a direction; the speed part of the velocity takes units of speed.

Flow (volume)

Flow
Name of unit Symbol Definition Relation to SI units
cubic foot per minute CFMTemplate:Citation needed ≡ 1 ft3/min = Template:Val
cubic foot per second ft3/s ≡ 1 ft3/s = Template:Val
cubic inch per minute in3/min ≡ 1 in3/min = Template:ValTemplate:OverlineTemplate:E m3/s
cubic inch per second in3/s ≡ 1 in3/s = Template:Val
cubic metre per second (SI unit) m3/s ≡ 1 m3/s = 1 m3/s
gallon (US fluid) per day GPDTemplate:Citation needed ≡ 1 gal/d = Template:ValTemplate:OverlineTemplate:E m3/s
gallon (US fluid) per hour GPHTemplate:Citation needed ≡ 1 gal/h = Template:ValTemplate:OverlineTemplate:E m3/s
gallon (US fluid) per minute GPMTemplate:Citation needed ≡ 1 gal/min = Template:Val
litre per minute l/min or L/min ≡ 1 L/min = 1.Template:OverlineTemplate:E m3/s

Acceleration

Acceleration
Name of unit Symbol Definition Relation to SI units
foot per hour per second fph/s ≡ 1 ft/(h⋅s) = 8.4Template:OverlineTemplate:E m/s2
foot per minute per second fpm/s ≡ 1 ft/(min⋅s) = Template:Val
foot per second squared fps2 ≡ 1 ft/s2 = Template:Val
gal; galileo Gal ≡ 1 cm/s2 = 10−2 m/s2
inch per minute per second ipm/s ≡ 1 in/(min⋅s) = 4.2Template:OverlineTemplate:E m/s2
inch per second squared ips2 ≡ 1 in/s2 = Template:Val
knot per second kn/s ≡ 1 kn/s ≈ 5.1Template:OverlineTemplate:E m/s2
metre per second squared (SI unit) m/s2 ≡ 1 m/s2 = 1 m/s2
mile per hour per second mph/s ≡ 1 mi/(h⋅s) = Template:Val
mile per minute per second mpm/s ≡ 1 mi/(min⋅s) = 26.8224 m/s2
mile per second squared mps2 ≡ 1 mi/s2 = Template:Val
standard gravity g0 Template:Val = Template:Val

Force

Template:See also

Force
Name of unit Symbol Definition Relation to SI units
atomic unit of force Template:Frac Template:Val[30]
dyne (CGS unit) dyn ≡ g⋅cm/s2 = 10−5 N
kilogram-force; kilopond; grave-force kgf; kp; gvf g0 × 1 kg = Template:Val
kip; kip-force kip; kipf; klbf g0 × Template:Val = Template:Val
milligrave-force, gravet-force mgvf; gvtf g0 × 1 g = Template:Val
long ton-force tnfTemplate:Citation needed g0 × 1 long ton = Template:Val
newton (SI unit) N A force capable of giving a mass of one kilogram an acceleration of one metre per second per second.[31] = 1 N = 1 kg⋅m/s2
ounce-force ozf g0 × 1 oz = Template:Val
pound-force lbf g0 × 1 lb = Template:Val
poundal pdl ≡ 1 lb⋅ft/s2 = Template:Val
short ton-force tnfTemplate:Citation needed g0 × 1 short ton = Template:Val
sthene (mts unit) sn ≡ 1 t⋅m/s2 = 103 N

Pressure or mechanical stress

Pressure
Name of unit Symbol Definition Relation to SI units
atmosphere (standard) atm Template:Val[32]
atmosphere (technical) at ≡ 1 kgf/cm2 = Template:Val[32]
bar bar Template:Val Pa ≡ 105 Pa
barye (CGS unit)   ≡ 1 dyn/cm2 = 0.1 Pa
centimetre of mercury cmHg Template:Val × 1 cm × g0 Template:Val[32]
centimetre of water (4 °C) cmH2O ≈ 999.972 kg/m3 × 1 cm × g0 Template:Val[32]
foot of mercury (conventional) ftHg Template:Val × 1 ft × g0 Template:Val[32]
foot of water (39.2 °F) ftH2O ≈ 999.972 kg/m3 × 1 ft × g0 Template:Val[32]
inch of mercury (conventional) inHg Template:Val × 1 in × g0 Template:Val[32]
inch of water (39.2 °F) inH2O ≈ 999.972 kg/m3 × 1 in × g0 Template:Val[32]
kilogram-force per square millimetre kgf/mm2 ≡ 1 kgf/mm2 = Template:Val[32]
kip per square inch ksi ≡ 1 kipf/sq in Template:Val[32]
long ton per square foot   ≡ 1 long ton × g0 / 1 sq ft Template:Val
micrometre of mercury μmHg Template:Val × 1 μm × g0 ≈ 0.001 torr Template:Val[32]
millimetre of mercury mmHg Template:Val × 1 mm × g0 ≈ 1 torr Template:Val[32]
millimetre of water (3.98 °C) mmH2O ≈ 999.972 kg/m3 × 1 mm × g0 = Template:Val = Template:Val
pascal (SI unit) Pa ≡ N/m2 = kg/(m⋅s2) = 1 Pa[33]
pièze (mts unit) pz Template:Val = Template:Val = 1 kPa
pound per square foot psf ≡ 1 lbf/ft2 Template:Val[32]
pound per square inch psi ≡ 1 lbf/in2 Template:Val[32]
poundal per square foot pdl/sq ft ≡ 1 pdl/sq ft Template:Val[32]
short ton per square foot   ≡ 1 short ton × g0 / 1 sq ft Template:Val
torr torr Template:Frac Pa Template:Val[32]

Torque or moment of force

Torque
Name of unit Symbol Definition Relation to SI units
pound-force-foot lbf⋅ft g0 × 1 lb × 1 ft = Template:Val
poundal-ft pdl⋅ft ≡ 1 lb⋅ft2/s2 = Template:Val
pound force-inch lbf⋅in g0 × 1 lb × 1 in = Template:Val
kilogram force-meter kgf⋅m g0 × N × m = Template:Val
Newton metre (SI unit) N⋅m ≡ N × m = kg⋅m2/s2 = Template:Val

Energy

Energy
Name of unit Symbol Definition Relation to SI units
barrel of oil equivalent boe Template:Val Template:Val
British thermal unit (ISO) BTUISO Template:Val = Template:Val
British thermal unit (International Table) BTUIT = Template:Val
British thermal unit (mean) BTUmean Template:Val
British thermal unit (thermochemical) BTUth Template:Val
British thermal unit (39 °F) BTU39 °F Template:Val
British thermal unit (59 °F) BTU59 °F Template:Val = Template:Val
British thermal unit (60 °F) BTU60 °F Template:Val
British thermal unit (63 °F) BTU63 °F Template:Val
calorie (International Table) calIT Template:Val = Template:Val
calorie (mean) calmean Template:Frac of the energy required to warm one gram of air-free water from 0 °C to 100 °C at a pressure of 1 atm Template:Val
calorie (thermochemical) calth ≡ 4.184 J = Template:Val
Calorie (US; FDA) Cal ≡ 1 kcal = Template:Val = Template:Val
calorie (3.98 °C) cal3.98 °C Template:Val
calorie (15 °C) cal15 °C ≡ 4.1855 J = Template:Val
calorie (20 °C) cal20 °C Template:Val
Celsius heat unit (International Table) CHUIT ≡ 1 BTUIT × 1 K/°R = Template:Val
cubic centimetre of atmosphere; standard cubic centimetre cc atm; scc ≡ 1 atm × 1 cm3 = Template:Val
cubic foot of atmosphere; standard cubic foot cu ft atm; scf ≡ 1 atm × 1 ft3 = Template:Val
cubic foot of natural gas   Template:Val = Template:Val
cubic yard of atmosphere; standard cubic yard cu yd atm; scy ≡ 1 atm × 1 yd3 = Template:Val
electronvolt eV e × 1 V Template:Val
erg (CGS unit) erg ≡ 1 g⋅cm2/s2 = 10−7 J
foot-pound force ft lbf g0 × 1 lb × 1 ft = Template:Val
foot-poundal ft pdl ≡ 1 lb⋅ft2/s2 = Template:Val
gallon-atmosphere (imperial) imp gal atm ≡ 1 atm × 1 gal (imp) = Template:Val
gallon-atmosphere (US) US gal atm ≡ 1 atm × 1 gal (US) = Template:Val
hartree, atomic unit of energy Eh ≡ meα2c2 (= 2 Ry) Template:Val
horsepower-hour hp⋅h ≡ 1 hp × 1 h = Template:Val
inch-pound force in lbf g0 × 1 lb × 1 in = Template:Val
joule (SI unit) J The work done when a force of one newton moves the point of its application a distance of one metre in the direction of the force.[31] = 1 J = 1 m⋅N = 1 kg⋅m2/s2 = 1 C⋅V = 1 W⋅s
kilocalorie; large calorie kcal; Cal Template:Val = Template:Val
kilowatt-hour; Board of Trade Unit kW⋅h; B.O.T.U. ≡ 1 kW × 1 h = Template:Val
litre-atmosphere l atm; sl ≡ 1 atm × 1 L = Template:Val
quad   ≡ 1015 BTUIT = Template:Val
rydberg Ry Rc Template:Val
therm (E.C.)   Template:Val = Template:Val
therm (US)   Template:Val = Template:Val
thermie th ≡ 1 McalIT = Template:Val
tonne of coal equivalent TCE ≡ 7 Gcalth = Template:Val
tonne of oil equivalent toe ≡ 10 GcalIT = Template:Val
ton of TNT tTNT ≡ 1 Gcalth = Template:Val
watt hour W⋅h ≡ 1 W × 1 h = Template:Val
watt second W⋅s ≡ 1 J = Template:Val

Power or heat flow rate

Power
Name of unit Symbol Definition Relation to SI units
atmosphere-cubic centimetre per minute atm ccmTemplate:Citation needed ≡ 1 atm × 1 cm3/min = Template:Val
atmosphere-cubic centimetre per second atm ccsTemplate:Citation needed ≡ 1 atm × 1 cm3/s = Template:Val
atmosphere-cubic foot per hour atm cfhTemplate:Citation needed ≡ 1 atm × 1 cu ft/h = Template:Val
atmosphere-cubic foot per minute atm cfmTemplate:Citation needed ≡ 1 atm × 1 cu ft/min = Template:Val
atmosphere-cubic foot per second atm cfsTemplate:Citation needed ≡ 1 atm × 1 cu ft/s = Template:Val
BTU (International Table) per hour BTUIT/h ≡ 1 BTUIT/h Template:Val
BTU (International Table) per minute BTUIT/min ≡ 1 BTUIT/min Template:Val
BTU (International Table) per second BTUIT/s ≡ 1 BTUIT/s = Template:Val
calorie (International Table) per second calIT/s ≡ 1 calIT/s = Template:Val
erg per second erg/s ≡ 1 erg/s = Template:Val
foot-pound-force per hour ft⋅lbf/h ≡ 1 ft lbf/h Template:Val
foot-pound-force per minute ft⋅lbf/min ≡ 1 ft lbf/min = Template:Val
foot-pound-force per second ft⋅lbf/s ≡ 1 ft lbf/s = Template:Val
horsepower (boiler) hp ≈ 34.5 lb/h × 970.3 BTUIT/lb Template:Val[34]
horsepower (European electrical) hp ≡ 75 kp⋅m/s = Template:ValTemplate:Citation needed
horsepower (electrical) hp ≡ 746 W = Template:Val[34]
horsepower (mechanical) hp ≡ 550 ft⋅lbf/s[34] = Template:Val
horsepower (metric) hp or PS ≡ 75 m⋅kgf/s = Template:Val[34]
litre-atmosphere per minute L·atm/min ≡ 1 atm × 1 L/min = Template:Val
litre-atmosphere per second L·atm/s ≡ 1 atm × 1 L/s = Template:Val
lusec lusec ≡ 1 L·µmHg/s [16] Template:Val
poncelet p ≡ 100 m⋅kgf/s = Template:Val
square foot equivalent direct radiation sq ft EDR ≡ 240 BTUIT/h Template:Val
ton of air conditioning   Template:Val of ice melted / 24 h Template:Val
ton of refrigeration (imperial)   Template:Val × iceIT / 24 h: iceIT = 144 °F × 2326 J/kg⋅°F Template:Val
ton of refrigeration (IT)   Template:Val × iceIT / 24 h: iceIT = 144 °F × 2326 J/kg⋅°F Template:Val
watt (SI unit) W The power which in one second of time gives rise to one joule of energy.[31] = Template:Val = 1 J/s = 1 N⋅m/s = 1 kg⋅m2/s3

Action

Action
Name of unit Symbol Definition Relation to SI units
atomic unit of action au Template:Frac Template:Val[35]

Dynamic viscosity

Dynamic viscosity
Name of unit Symbol Definition Relation to SI units
pascal second (SI unit) Pa⋅s ≡ N⋅s/m2, kg/(m⋅s) = 1 Pa⋅s
poise (CGS unit) P ≡ 1 barye⋅s = 0.1 Pa⋅s
pound per foot hour lb/(ft⋅h) ≡ 1 lb/(ft⋅h) Template:Val
pound per foot second lb/(ft⋅s) ≡ 1 lb/(ft⋅s) Template:Val
pound-force second per square foot lbf⋅s/ft2 ≡ 1 lbf⋅s/ft2 Template:Val
pound-force second per square inch lbf⋅s/in2 ≡ 1 lbf⋅s/in2 Template:Val

Kinematic viscosity

Kinematic viscosity
Name of unit Symbol Definition Relation to SI units
square foot per second ft2/s ≡ 1 ft2/s = Template:Val
square metre per second (SI unit) m2/s ≡ 1 m2/s = 1 m2/s
stokes (CGS unit) St ≡ 1 cm2/s = 10−4 m2/s

Electric current

Electric current
Name of unit Symbol Definition Relation to SI units
ampere (SI base unit) A ≡ one coulomb of charge going past a given point per second.[36] (SI base unit)
electromagnetic unit; abampere (CGS unit) abamp ≘ 10 A = 10 A
esu per second; statampere (CGS unit) esu/s ≘ (10 A⋅cm/s) / c Template:Val

Electric charge

Electric charge
Name of unit Symbol Definition Relation to SI units
abcoulomb; electromagnetic unit (CGS unit) abC; emu ≘ 10 C = 10 C
atomic unit of charge au e = Template:Val
coulomb C ≡ charge of exactly 1/(Template:Val) elementary charges[36] = 1 C = 1 A⋅s
faraday F ≡ 1 mol × NAe Template:Val
milliampere hour mA⋅h ≡ 0.001 A × 1 h = 3.6 C
statcoulomb; franklin; electrostatic unit (CGS unit) statC; Fr; esu ≘ (10 A⋅cm) / c Template:Val

Electric dipole

Electric dipole
Name of unit Symbol Definition Relation to SI units
atomic unit of electric dipole moment ea0   Template:Val[37]
coulomb-meter C⋅m   = 1 C⋅m
debye D ≡ 10−10 esu⋅Å Template:Val[38]

Electromotive force, electric potential difference

Voltage, electromotive force
Name of unit Symbol Definition Relation to SI units
abvolt (CGS unit) abV ≘ 10−8 V = 10−8 V
statvolt (CGS unit) statV c⋅(1 μJ/A⋅m) = Template:Val
volt (SI unit) V The difference in electric potential across two points along a conducting wire carrying one ampere of constant current when the power dissipated between the points equals one watt.[31] = 1 V = 1 W/A Template:Nowrap = 1 J/C

Electrical resistance

Electrical resistance
Name of unit Symbol Definition Relation to SI units
ohm (SI unit) Ω The resistance between two points in a conductor when one volt of electric potential difference, applied to these points, produces one ampere of current in the conductor.[31] = 1 Ω = 1 V/A Template:Nowrap

Capacitance

Capacitor's ability to store charge
Name of unit Symbol Definition Relation to SI units
farad (SI unit) F The capacitance between two parallel plates that results in one volt of potential difference when charged by one coulomb of electricity.[31] = 1 F = 1 C/V Template:Nowrap

Magnetic flux

Magnetic flux
Name of unit Symbol Definition Relation to SI units
maxwell (CGS unit) Mx ≘ 10−8 Wb[34] = 10−8 Wb
weber (SI unit) Wb Magnetic flux which, linking a circuit of one turn, would produce in it an electromotive force of 1 volt if it were reduced to zero at a uniform rate in 1 second.[31] = 1 Wb = 1 V⋅s Template:Nowrap

Magnetic flux density

What physicists call magnetic field is called magnetic flux density by electrical engineers and magnetic induction by applied mathematicians and electrical engineers.
Name of unit Symbol Definition Relation to SI units
gauss (CGS unit) G Mx/cm2 ≘ 10−4 T = 10−4 T [39]
tesla (SI unit) T Wb/m2 = 1 T = 1 Wb/m2 Template:Nowrap

Inductance

Inductance
Name of unit Symbol Definition Relation to SI units
henry (SI unit) H The inductance of a closed circuit that produces one volt of electromotive force when the current in the circuit varies at a uniform rate of one ampere per second.[31] = 1 H = 1 Wb/A Template:Nowrap

Temperature

Template:Details

Temperature
Name of unit Symbol Definition Relation to SI units
degree Celsius °C [°C] ≡ [K] − 273.15 [K] ≡ [°C] + 273.15
degree Delisle °De [K] = 373.15 − [°De] × Template:Frac
degree Fahrenheit °F [°F] ≡ [°C] × Template:Frac + 32 [K] ≡ ([°F] + 459.67) × Template:Frac
degree Newton °N [K] = [°N] × Template:Frac + 273.15
degree Rankine °R; [°R] ≡ [K] × Template:Frac [K] ≡ [°R] × 5/9
degree Réaumur °Ré [K] = [°Ré] × Template:Frac + 273.15
degree Rømer °Rø [K] = ([°Rø] − 7.5) × Template:Frac + 273.15
Regulo Gas Mark GM [°F] ≡ [GM] × 25 + 300 [K] ≡ [GM] × Template:Frac + 422.038
kelvin (SI base unit) K ≡ change in the thermodynamic temperature T that results in a change of thermal energy kT by 1.380 649 × 10−23 J.[40] (SI base unit)

Information entropy

Information entropy
Name of unit Symbol Definition Relation to SI units Relation to bits
natural unit of information; nit; nepit nat
shannon Sh ≡ ln(2) × nat Template:Val = 1 bit
hartley; ban Hart; ban ≡ ln(10) × nat Template:Val
bit bit; b = 1 bit
nibble ≡ 4 bits = 22 bit
byte B ≡ 8 bits = 23 bit
kilobyte (decimal) kB Template:Val = Template:Val bit
kibibyte (kilobyte) KiB; KB Template:Val = 213 bit = Template:Val bit

Modern standards (such as ISO 80000) prefer the shannon to the bit as a unit for a quantity of information entropy, whereas the (discrete) storage space of digital devices is measured in bits. Thus, uncompressed redundant data occupy more than one bit of storage per shannon of information entropy. The multiples of a bit listed above are usually used with this meaning.

Luminous intensity

The candela is the preferred nomenclature for the SI unit.

Luminous intensity
Name of unit Symbol Definition Relation to SI units
candela (SI base unit) cd The luminous intensity, in a given direction, of a source that emits monochromatic radiation of frequency 540Template:E hertz and that has a radiant intensity in that direction of 1/683 watt per steradian.[36] (SI base unit)
candlepower (new) cp ≡ cd The use of candlepower as a unit is discouraged due to its ambiguity. = 1 cd
candlepower (old, pre-1948) cp Varies and is poorly reproducible.[41] Approximately 0.981 cd.[16] ≈ 0.981 cd

Luminance

Luminance
Name of unit Symbol Definition Relation to SI units
candela per square foot cd/ft2 ≡ cd/ft2 Template:Val
candela per square inch cd/in2 ≡ cd/in2 Template:Val
candela per square metre (SI unit); nit (deprecated[16]) cd/m2 ≡ cd/m2 = 1 cd/m2
footlambert fL ≡ (1/π) cd/ft2 Template:Val
lambert L ≡ (104/π) cd/m2 Template:Val
stilb (CGS unit) sb ≡ 104 cd/m2 = 104 cd/m2

Luminous flux

Luminous flux
Name of unit Symbol Definition Relation to SI units
lumen (SI unit) lm The luminous flux of a source that emits monochromatic radiation of frequency 540Template:E hertz and that has a radiant flux of 1/683 watt.[36] = 1 lm = 1 cd⋅sr

Illuminance

Illuminance
Name of unit Symbol Definition Relation to SI units
footcandle; lumen per square foot fc ≡ lm/ft2 = Template:Val
lumen per square inch lm/in2 ≡ lm/in2 Template:Val
lux (SI unit) lx ≡ lm/m2 = 1 lx = 1 lm/m2
phot (CGS unit) ph ≡ lm/cm2 = 104 lx

Radiation – source activity

Radioactivity
Name of unit Symbol Definition Relation to SI units
becquerel (SI unit) Bq ≡ Number of disintegrations per second = 1 Bq = 1/s
curie Ci Template:Val[42] = Template:Val
rutherford (H) Rd ≡ 1 MBq = 106 Bq

Although becquerel (Bq) and hertz (Hz) both ultimately refer to the same SI base unit (s−1), Hz is used only for periodic phenomena (i.e. repetitions at regular intervals), and Bq is only used for stochastic processes (i.e. at random intervals) associated with radioactivity.[43]

Radiation – exposure

Radiation – exposure
Name of unit Symbol Definition Relation to SI units
roentgen R 1 R ≡ Template:Val[34] = Template:Val

The roentgen is not an SI unit and the NIST strongly discourages its continued use.[44]

Radiation – absorbed dose

Radiation – absorbed dose
Name of unit Symbol Definition Relation to SI units
gray (SI unit) Gy ≡ 1 J/kg[45] = 1 Gy = 1 J/kg = 1 m2⋅s2
rad rad ≡ 0.01 Gy[34] = 0.01 Gy

Radiation – equivalent dose

Radiation – equivalent dose
Name of unit Symbol Definition Relation to SI units
Röntgen equivalent man rem ≡ 0.01 Sv = 0.01 Sv
sievert (SI unit) Sv ≡ 1 J/kg[43] = 1 Sv = 1 J/kg = 1 m2⋅s2

Although the definitions for sievert (Sv) and gray (Gy) would seem to indicate that they measure the same quantities, this is not the case. The effect of receiving a certain dose of radiation (given as Gy) is variable and depends on many factors, thus a new unit was needed to denote the biological effectiveness of that dose on the body; this is known as the equivalent dose and is shown in Sv. The general relationship between absorbed dose and equivalent dose can be represented as

H = QD

where H is the equivalent dose, D is the absorbed dose, and Q is a dimensionless quality factor. Thus, for any quantity of D measured in Gy, the numerical value for H measured in Sv may be different.

Licensing

Content obtained and/or adapted from:

  • Template:Cite journal
  • "NIST Reference on Constants, Units, and Uncertainty."(2010). National Institute of Standards and Technology. Retrieved October 17, 2014.
  • 3.0 3.1 3.2 3.3 3.4 Template:Cite web
  • 4.00 4.01 4.02 4.03 4.04 4.05 4.06 4.07 4.08 4.09 4.10 4.11 4.12 4.13 Lide, D. (Ed.). (1990). Handbook of Chemistry and Physics (71st ed). Boca Raton, FL: CRC Press. Section 1.
  • 5.0 5.1 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.
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