Conversion of units

For the conversion of units on wikipedia, see Template:Convert.

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

Techniques

See also: Dimensional analysis

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
• 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.

Multiplication factors

Conversion between units in the metric 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).

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.

Legend

Symbol	Definition
≡	exactly equal to
≈	approximately equal to
digits	indicates that digits repeat infinitely (e.g. 8.294369 corresponds to 8.294369369369369…)
(H)	of chiefly historical interest

Length

Length

Name of unit	Symbol	Definition	Relation to SI units
ångström	Å	≡ 1×10−10 m	≡ 0.1 nm
astronomical unit	AU	≡ 149597870700 m ≈ Distance from Earth to Sun	≡ 149597870700 m
barleycorn (H)		= 1⁄3 in (see note above about rounding)	≈ 8.46×10−3 m
bohr, atomic unit of length	a0	= Bohr radius of hydrogen	≈ 5.2917721092×10−11 m  ± 1.7×10−20 m
cable length (imperial)		≡ 608 ft	≈ 185.3184 m
cable length (International)		≡ 1⁄10 nmi	≡ 185.2 m
cable length (US)		≡ 720 ft	= 219.456 m
chain (Gunter's; Surveyor's)	ch	≡ 66 ft(US) ≡ 4 rods	≈ 20.11684 m
cubit (H)		≡ Distance from fingers to elbow ≈ 18 in	≈ 0.5 m
ell (H)	ell	≡ 45 in (In England usually)	= 1.143 m
fathom	fm	≡ 6 ft	= 1.8288 m
fermi	fm	≡ 1×10−15 m	≡ 1×10−15 m
finger		≡ 7⁄8 in	= 0.022225 m
finger (cloth)		≡ 4+1⁄2 in	= 0.1143 m
foot (Benoît) (H)	ft (Ben)		≈ 0.304799735 m
foot (Cape) (H)		Legally defined as 1.033 English feet in 1859	≈ 0.314858 m
foot (Clarke's) (H)	ft (Cla)		≈ 0.3047972654 m
foot (Indian) (H)	ft Ind		≈ 0.304799514 m
foot (International)	ft	≡ 0.3048 m ≡ 1⁄3 yd ≡ 12 inches	≡ 0.3048 m
foot (Sear's) (H)	ft (Sear)		≈ 0.30479947 m
foot (US Survey)	ft (US)	≡ 1200⁄3937 m	≈ 0.304800610 m
french; charriere	F	≡ 1⁄3 mm	= 0.3 ×10−3 m
furlong	fur	≡ 10 chains = 660 ft = 220 yd	= 201.168 m
hand		≡ 4 in	≡ 0.1016 m
inch (International)	in	≡ 2.54 cm ≡ 1⁄36 yd ≡ 1⁄12 ft	≡ .0254 m
league (land)	lea	≈ 1 hour walk, Currently defined in US as 3 Statute miles, but historically varied from 2 to 9 km	≈ 4828 m
light-day		≡ 24 light-hours	≡ 2.59020683712×1013 m
light-hour		≡ 60 light-minutes	≡ 1.0792528488×1012 m
light-minute		≡ 60 light-seconds	≡ 1.798754748×1010 m
light-second		≡ Distance light travels in one second in vacuum	≡ 299792458 m
light-year	ly	≡ Distance light travels in vacuum in 365.25 days	= 9.4607304725808×1015 m
line	ln	≡ 1⁄12 in	= 0.002116 m
link (Gunter's; Surveyor's)	lnk	100}} ch ≡ 0.66 ft ≡ 7.92 in	= 0.201168 m
link (Ramsden's; Engineer's)	lnk	≡ 1 ft	= 0.3048 m
metre (SI base unit) (meter)	m	≡ Distance light travels in 1⁄299792458 of a second in vacuum. ≈ 1⁄10000000 of the distance from equator to pole.	≡ 1 m
mickey		≡ 1⁄200 in	= 1.27×10−4 m
micron	µ		≡ 1×10−6 m
mil; thou	mil	≡ 1×10−3 in	≡ 2.54×10−5 m
mil (Sweden and Norway)	mil	≡ 10 km	= 10000 m
mile (geographical) (H)		≡ 6082 ft	= 1853.7936 m
mile (international)	mi	≡ 80 chains ≡ 5280 ft ≡ 1760 yd	≡ 1609.344 m
mile (tactical or data)		≡ 6000 ft	≡ 1828.8 m
mile (telegraph) (H)	mi	≡ 6087 ft	= 1855.3176 m
mile (US Survey)	mi	≡ 5280 US Survey feet ≡ (5280 × 1200⁄3937) m	≈ 1609.347219 m
nail (cloth)		≡ 2+1⁄4 in	= 0.05715 m
nanometre	nm	≡ 1×10−9 m	≡ 1×10−9 m
nautical league	NL; nl	≡ 3 nmi	= 5556 m
nautical mile (Admiralty)	NM (Adm); nmi (Adm)	= 6080 ft	= 1853.184 m
nautical mile (international)	NM; nmi	≡ 1852 m	≡ 1852 m
nautical mile (US pre 1954)		≡ 1853.248 m	≡ 1853.248 m
pace		≡ 2.5 ft	= 0.762 m
palm		≡ 3 in	= 0.0762 m
parsec	pc	Distance of star with parallax shift of one arc second from a base of one astronomical unit	≈ 3.08567782×1016 ± 6×106 m
pica		≡ 12 points	Dependent on point measures.
point (American, English)	pt	≡ 1⁄72.272 in	≈ 0.000351450 m
point (Didot; European)	pt	≡ 1⁄12 × 1⁄72 of pied du roi; After 1878: ≡ 5/133 cm	≈ 0.00037597 m; After 1878: ≈ 0.000 375 939 85 m
point (PostScript)	pt	≡ 1⁄72 in	= 0.0003527 m
point (TeX)	pt	≡ 1⁄72.27 in	= 0.0003514598 m
quarter		≡ 1⁄4 yd	= 0.2286 m
rod; pole; perch (H)	rd	≡ 16+1⁄2 ft	= 5.0292 m
rope (H)	rope	≡ 20 ft	= 6.096 m
shaku (Japan)			= 0.3030 m
span (H)		≡ 9 in	= 0.2286 m
spat			≡ 1×1012 m
stick (H)		≡ 2 in	= 0.0508 m
stigma; bicron (picometre)	pm		≡ 1×10−12 m
twip	twp	≡ 1⁄1440 in	= 1.7638×10−5 m
x unit; siegbahn	xu		≈ 1.0021×10−13 m
yard (International)	yd	≡ 0.9144 m ≡ 3 ft ≡ 36 in	≡ 0.9144 m

Area

Area

Name of unit	Symbol	Definition	Relation to SI units
acre (international)	ac	≡ 1 ch × 10 ch = 4840 sq yd	≡ 4 046.856 4224 m2
acre (U. S. survey)	ac	≡ 10 sq ch = 4840 sq yd, also 43560 sq ft.	≈ 4 046.873 m2
are	a	≡ 100 m2	= 100 m2
barn	b	≡ 10−28 m2	= 10−28 m2
barony		≡ 4000 ac	≈ 1.618 742×107 m2
board	bd	≡ 1 in × 1 ft	= 7.741 92×10−3 m2
boiler horsepower equivalent direct radiation	bhp EDR	≡ (1 ft2) (1 bhp) / (240 BTUIT/h)	≈ 12.958 174 m2
circular inch	circ in	≡ π/4 sq in	≈ 5.067 075×10−4 m2
circular mil; circular thou	circ mil	≡ π/4 mil2	≈ 5.067 075×10−10 m2
cord		≡ 192 bd	= 1.486 448 64 m2
cuerda (PR Survey)	cda	≡ 1 cda x 1 cda = 0.971222 acre	≡ 3930.395625 m2
dunam		≡ 1 000 m2	= 1 000 m2
guntha		≡ 121 sq yd	≈ 101.17 m2
hectare	ha	≡ 10 000 m2	≡ 10 000 m2
hide		≈ 120 ac (variable)	≈ 5×105 m2
rood	ro	≡ ¼ ac	= 1 011.714 1056 m2
section		≡ 1 mi × 1 mi	= 2.589 988 110 336×106 m2
shed		≡ 10−52 m2	= 10−52 m2
square (roofing)		≡ 10 ft × 10 ft	= 9.290 304 m2
square chain (international)	sq ch	≡ 66 ft × 66 ft = 1/10 ac	≡ 404.685 642 24 m2
square chain (US Survey)	sq ch	≡ 66 ft(US) × 66 ft(US) = 1/10 ac	≈ 404.687 3 m2
square foot	sq ft	≡ 1 ft × 1 ft	≡ 9.290 304×10−2 m2
square foot (US Survey)	sq ft	≡ 1 ft (US) × 1 ft (US)	≈ 9.290 341 161 327 49×10−2 m2
square inch	sq in	≡ 1 in × 1 in	≡ 6.4516×10−4 m2
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	= 4.046 856 4224×10−2 m2
square link (Gunter's)(US Survey)	sq lnk	≡ 1 lnk × 1 lnk ≡ 0.66 ft(US) × 0.66 ft(US)	≈ 4.046 872×10−2 m2
square link (Ramsden's)	sq lnk	≡ 1 lnk × 1 lnk ≡ 1 ft × 1 ft	= 0.09290304 m2
square metre (SI unit)	m2	≡ 1 m × 1 m	= 1 m2
square mil; square thou	sq mil	≡ 1 mil × 1 mil	= 6.4516×10−10 m2
square mile	sq mi	≡ 1 mi × 1 mi	= 2.589 988 110 336×106 m2
square mile (US Survey)	sq mi	≡ 1 mi (US) × 1 mi (US)	≈ 2.589 998 47×106 m2
square rod/pole/perch	sq rd	≡ 1 rd × 1 rd	= 25.292 852 64 m2
square yard (International)	sq yd	≡ 1 yd × 1 yd	≡ 0.836 127 36 m2
stremma		≡ 1 000 m2	= 1 000 m2
township		≡ 36 sq mi (US)	≈ 9.323 994×107 m2
yardland		≈ 30 ac	≈ 1.2×105 m2

Volume

Volume

Name of unit	Symbol	Definition	Relation to SI units
acre-foot	ac ft	≡ 1 ac x 1 ft = 43 560 ft3	= 1 233.481 837 547 52 m3
acre-inch		≡ 1 ac × 1 in	= 102.790 153 128 96 m3
barrel (imperial)	bl (imp)	≡ 36 gal (imp)	= 0.163 659 24 m3
barrel (petroleum)	bl; bbl	≡ 42 gal (US)	= 0.158 987 294 928 m3
barrel (US dry)	bl (US)	≡ 105 qt (US) = 105/32 bu (US lvl)	= 0.115 628 198 985 075 m3
barrel (US fluid)	fl bl (US)	≡ 31½ gal (US)	= 0.119 240 471 196 m3
board-foot	fbm	≡ 144 cu in	≡ 2.359 737 216×10−3 m3
bucket (imperial)	bkt	≡ 4 gal (imp)	= 0.018 184 36 m3
bushel (imperial)	bu (imp)	≡ 8 gal (imp)	= 0.036 368 72 m3
bushel (US dry heaped)	bu (US)	≡ 1 ¼ bu (US lvl)	= 0.044 048 837 7086 m3
bushel (US dry level)	bu (US lvl)	≡ 2 150.42 cu in	= 0.035 239 070 166 88 m3
butt, pipe		≡ 126 gal (wine)	= 0.476 961 884 784 m3
coomb		≡ 4 bu (imp)	= 0.145 474 88 m3
cord (firewood)		≡ 8 ft × 4 ft × 4 ft	= 3.624 556 363 776 m3
cord-foot		≡ 16 cu ft	= 0.453 069 545 472 m3
cubic fathom	cu fm	≡ 1 fm × 1 fm × 1 fm	= 6.116 438 863 872 m3
cubic foot	cu ft	≡ 1 ft × 1 ft × 1 ft	≡ 0.028 316 846 592 m3
cubic inch	cu in	≡ 1 in × 1 in × 1 in	≡ 16.387 064×10−6 m3
cubic metre (SI unit)	m3	≡ 1 m × 1 m × 1 m	≡ 1 m3
cubic mile	cu mi	≡ 1 mi × 1 mi × 1 mi	≡ 4 168 181 825.440 579 584 m3
cubic yard	cu yd	≡ 27 cu ft	≡ 0.764 554 857 984 m3
cup (breakfast)		≡ 10 fl oz (imp)	= 284.130 625×10−6 m3
cup (Canadian)	c (CA)	≡ 8 fl oz (imp)	= 227.3045×10−6 m3
cup (metric)	c	≡ 250.0×10−6 m3	= 250.0×10−6 m3
cup (US customary)	c (US)	≡ 8 US fl oz ≡ 1/16 gal (US)	= 236.588 2365×10−6 m3
cup (US food nutrition labeling)	c (US)	≡ 240 mL	= 2.4×10−4 m3
dash (imperial)		≡ 1/384 gi (imp) = ½ pinch (imp)	= 369.961 751 302 08 3×10−9 m3
dash (US)		≡ 1/96 US fl oz = ½ US pinch	= 308.057 599 609 375×10−9 m3
dessertspoon (imperial)		≡ 1/12 gi (imp)	= 11.838 776 0416×10−6 m3
drop (imperial)	gtt	≡ 1/288 fl oz (imp)	= 98.656 467 013 8×10−9 m3
drop (imperial) (alt)	gtt	≡ 1/1 824 gi (imp)	≈ 77.886 684×10−9 m3
drop (medical)		≡ 0.9964/12 ml	= 83.03×10−9 m3
drop (medical)		≡ 1/12 ml	= 83.3×10−9 m3
drop (metric)		≡ 1/20 mL	= 50.0×10−9 m3
drop (US)	gtt	≡ 1/360 US fl oz	= 82.148 693 22916×10−9 m3
drop (US) (alt)	gtt	≡ 1/456 US fl oz	≈ 64.854 231 496 71×10−9 m3
drop (US) (alt)	gtt	≡ 1/576 US fl oz	≈ 51.342 933 268 23×10−9 m3
fifth		≡ 1/5 US gal	= 757.082 3568×10−6 m3
firkin		≡ 9 gal (imp)	= 0.040 914 81 m3
fluid drachm (imperial)	fl dr	≡ ⅛ fl oz (imp)	= 3.551 632 8125×10−6 m3
fluid dram (US); US fluidram	fl dr	≡ ⅛ US fl oz	= 3.696 691 195 3125×10−6 m3
fluid scruple (imperial)	fl s	≡ 1/24 fl oz (imp)	= 1.183 877 60416×10−6 m3
gallon (beer)	beer gal	≡ 282 cu in	= 4.621 152 048×10−3 m3
gallon (imperial)	gal (imp)	≡ 4.546  09 L	≡ 4.546 09×10−3 m3
gallon (US dry)	gal (US)	≡ ⅛ bu (US lvl)	= 4.404 883 770 86×10−3 m3
gallon (US fluid; Wine)	gal (US)	≡ 231 cu in	≡ 3.785 411 784×10−3 m3
gill (imperial); Noggin	gi (imp); nog	≡ 5 fl oz (imp)	= 142.065 3125×10−6 m3
gill (US)	gi (US)	≡ 4 US fl oz	= 118.294 118 25×10−6 m3
hogshead (imperial)	hhd (imp)	≡ 2 bl (imp)	= 0.327 318 48 m3
hogshead (US)	hhd (US)	≡ 2 fl bl (US)	= 0.238 480 942 392 m3
jigger (bartending)		≡ 1½ US fl oz	≈ 44.36×10−6 m3
kilderkin		≡ 18 gal (imp)	= 0.081 829 62 m3
lambda	λ	≡ 1 mm3	= 1×10−9 m3
last		≡ 80 bu (imp)	= 2.909 4976 m3
litre (liter)	L	≡ 1 dm3	≡ 0.001 m3
load		≡ 50 cu ft	= 1.415 842 3296 m3
minim (imperial)	min	≡ 1/480 fl oz (imp) = 1/60 fl dr (imp)	= 59.193 880 208 3×10−9 m3
minim (US)	min	≡ 1/480 US fl oz = 1/60 US fl dr	= 61.611 519 921 875×10−9 m3
ounce (fluid imperial)	fl oz (imp)	≡ 1/160 gal (imp)	≡ 28.413 0625×10−6 m3
ounce (fluid US customary)	US fl oz	≡ 1/128 gal (US)	≡ 29.573 529 5625×10−6 m3
ounce (fluid US food nutrition labeling)	US fl oz	≡ 30 mL	≡ 3×10−5 m3
peck (imperial)	pk	≡ 2 gal (imp)	= 9.092 18×10−3 m3
peck (US dry)	pk	≡ ¼ US lvl bu	= 8.809 767 541 72×10−3 m3
perch	per	≡ 16½ ft × 1½ ft × 1 ft	= 0.700 841 953 152 m3
pinch (imperial)		≡ 1/192 gi (imp) = ⅛ tsp (imp)	= 739.923 502 60416×10−9 m3
pinch (US)		≡ 1/48 US fl oz = ⅛ US tsp	= 616.115 199 218 75×10−9 m3
pint (imperial)	pt (imp)	≡ ⅛ gal (imp)	= 568.261 25×10−6 m3
pint (US dry)	pt (US dry)	≡ 1/64 bu (US lvl) ≡ ⅛ gal (US dry)	= 550.610 471 3575×10−6 m3
pint (US fluid)	pt (US fl)	≡ ⅛ gal (US)	= 473.176 473×10−6 m3
pony		≡ 3/4 US fl oz	= 22.180 147 171 875×10−6 m3
pottle; quartern		≡ ½ gal (imp) = 80 fl oz (imp)	= 2.273 045×10−3 m3
quart (imperial)	qt (imp)	≡ ¼ gal (imp)	= 1.136 5225×10−3 m3
quart (US dry)	qt (US)	≡ 1/32 bu (US lvl) = ¼ gal (US dry)	= 1.101 220 942 715×10−3 m3
quart (US fluid)	qt (US)	≡ ¼ gal (US fl)	= 946.352 946×10−6 m3
quarter; pail		≡ 8 bu (imp)	= 0.290 949 76 m3
register ton		≡ 100 cu ft	= 2.831 684 6592 m3
sack (imperial); bag		≡ 3 bu (imp)	= 0.109 106 16 m3
sack (US)		≡ 3 bu (US lvl)	= 0.105 717 210 500 64 m3
seam		≡ 8 bu (US lvl)	= 0.281 912 561 335 04 m3
shot (US)		usually 1.5 US fl oz	≈ 44×10−6 m3
strike (imperial)		≡ 2 bu (imp)	= 0.072 737 44 m3
strike (US)		≡ 2 bu (US lvl)	= 0.070 478 140 333 76 m3
tablespoon (Australian metric)			≡ 20.0×10−6 m3
tablespoon (Canadian)	tbsp	≡ ½ fl oz (imp)	= 14.206 531 25×10−6 m3
tablespoon (imperial)	tbsp	≡ 5/8 fl oz (imp)	= 17.758 164 0625×10−6 m3
tablespoon (metric)			≡ 15.0×10−6 m3
tablespoon (US customary)	tbsp	≡ ½ US fl oz	= 14.786 764 7825×10−6 m3
tablespoon (US food nutrition labeling)	tbsp	≡ 15 mL	= 1.5×10−5 m3
teaspoon (Canadian)	tsp	≡ 1/6 fl oz (imp)	= 4.735 510 416×10−6 m3
teaspoon (imperial)	tsp	≡ 1/24 gi (imp)	= 5.919 388 02083×10−6 m3
teaspoon (metric)		≡ 5.0×10−6 m3	= 5.0×10−6 m3
teaspoon (US customary)	tsp	≡ 1/6 US fl oz	= 4.928 921 595×10−6 m3
teaspoon (US food nutrition labeling)	tsp	≡ 5 mL	= 5×10−6 m3
timber foot		≡ 1 cu ft	= 0.028 316 846 592 m3
ton (displacement)		≡ 35 cu ft	= 0.991 089 630 72 m3
ton (freight)		≡ 40 cu ft	= 1.132 673 863 68 m3
ton (water)		≡ 28 bu (imp)	= 1.018 324 16 m3
tun		≡ 252 gal (wine)	= 0.953 923 769 568 m3
wey (US)		≡ 40 bu (US lvl)	= 1.409 562 806 6752 m3

Plane angle

Plane angle

Name of unit	Symbol	Definition	Relation to SI units
angular mil	µ	≡ 2π/6400 rad	≈ 0.981 748×10−3 rad
arcminute; MOA	'	≡ 1°/60	≈ 0.290 888×10−3 rad
arcsecond	"	≡ 1°/3600	≈ 4.848 137×10−6 rad
centesimal minute of arc	'	≡ 1 grad/100	≈ 0.157 080×10−3 rad
centesimal second of arc	"	≡ 1 grad/(10 000)	≈ 1.570 796×10−6 rad
degree (of arc)	°	≡ 1/360 of a revolution ≡ π/180 rad	≈ 17.453 293×10−3 rad
grad; gradian; gon	grad	≡ 1/400 of a revolution ≡ 2π/400 rad ≡ 0.9°	≈ 15.707 963×10−3 rad
octant		≡ 45°	≈ 0.785 398 rad
quadrant		≡ 90°	≈ 1.570 796 rad
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°	≈ 1.047 198 rad
sign		≡ 30°	≈ 0.523 599 rad

Solid angle

Solid angle

Name of unit	Symbol	Definition	Relation to SI units
square degree	deg²; sq.deg.; (°)²	≡ (π/180)² sr	≈ 0.30462×10−3 sr
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 encompasses 4π sr.	= 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 unit gee is used to denote standard gravity in order to avoid confusion with the "g" symbol for grams.
• 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		≈ 1.660 538 73×10−27 ± 1.3×10−36 kg
atomic unit of mass, electron rest mass	me		≈ 9.109 382 15×10−31 ± 45×10−39 kg
bag (coffee)		≡ 60 kg	= 60 kg
bag (Portland cement)		≡ 94 lb av	= 42.637 682 78 kg
barge		≡ 22½ sh tn	= 20 411.656 65 kg
carat	kt	≡ 3 1/6 gr	≈ 205.196 548 333 mg
carat (metric)	ct	≡ 200 mg	= 200 mg
clove		≡ 8 lb av	= 3.628 738 96 kg
crith			≈ 89.9349 mg
dalton	Da		≈ 1.660 902 10×10−27 ± 1.3×10−36 kg
dram (apothecary; troy)	dr t	≡ 60 gr	= 3.887 9346 g
dram (avoirdupois)	dr av	≡ 27 11/32 gr	= 1.771 845 195 3125 g
electronvolt	eV	≡ 1 eV (energy unit) / c2	= 1.7826×10−36 kg
gamma	γ	≡ 1 μg	= 1 μg
grain	gr	≡ 1/7000 lb av	≡ 64.798 91 mg
grave	G	grave was the original name of the kilogram	≡ 1 kg
hundredweight (long)	long cwt or cwt	≡ 112 lb av	= 50.802 345 44 kg
hundredweight (short); cental	sh cwt	≡ 100 lb av	= 45.359 237 kg
kilogram (kilogramme)	kg	≡ mass of the prototype near Paris (≈ mass of 1L of water)	≡ 1 kg (SI base unit)
kip	kip	≡ 1000 lb av	= 453.592 37 kg
mark		≡ 8 oz t	= 248.827 8144 g
mite		≡ 1/20 gr	= 3.239 9455 mg
mite (metric)		≡ 1/20 g	= 50 mg
ounce (apothecary; troy)	oz t	≡ 1/12 lb t	= 31.103 4768 g
ounce (avoirdupois)	oz av	≡ 1/16 lb	= 28.349 523 125 g
ounce (US food nutrition labeling)	oz	≡ 28 g	= 28 g
pennyweight	dwt; pwt	≡ 1/20 oz t	= 1.555 173 84 g
point		≡ 1/100 ct	= 2 mg
pound	lb	≡ slug·ft/s2	= 0.45359237 kg
pound (avoirdupois)	lb av	≡ 0.453 592 37 kg = 7000 grains	≡ 0.453 592 37 kg
pound (metric)		≡ 500 g	= 500 g
pound (troy)	lb t	≡ 5 760 grains	= 0.373 241 7216 kg
quarter (imperial)		≡ 1/4 long cwt = 2 st = 28 lb av	= 12.700 586 36 kg
quarter (informal)		≡ ¼ short tn	= 226.796 185 kg
quarter, long (informal)		≡ ¼ long tn	= 254.011 7272 kg
quintal (metric)	q	≡ 100 kg	= 100 kg
scruple (apothecary)	s ap	≡ 20 gr	= 1.295 9782 g
sheet		≡ 1/700 lb av	= 647.9891 mg
slug; geepound; hyl	slug	≡ 1 gee × 1 lb av × 1 s2/ft	≈ 14.593 903 kg
stone	st	≡ 14 lb av	= 6.350 293 18 kg
ton, assay (long)	AT	≡ 1 mg × 1 long tn ÷ 1 oz t	≈ 32.666 667 g
ton, assay (short)	AT	≡ 1 mg × 1 sh tn ÷ 1 oz t	≈ 29.166 667 g
ton, long	long tn or ton	≡ 2 240 lb	= 1 016.046 9088 kg
ton, short	sh tn	≡ 2 000 lb	= 907.184 74 kg
tonne (mts unit)	t	≡ 1 000 kg	= 1 000 kg
wey		≡ 252 lb = 18 st	= 114.305 277 24 kg (variants exist)
Zentner	Ztr.	Definitions vary; see and.

Density

Density

Name of unit	Symbol	Definition	Relation to SI units
gram per millilitre	g/mL	≡ g/mL	= 1,000 kg/m3
kilogram per cubic metre (SI unit)	kg/m3	≡ kg/m3	= 1 kg/m3
kilogram per litre	kg/L	≡ kg/L	= 1,000 kg/m3
ounce (avoirdupois) per cubic foot	oz/ft3	≡ oz/ft3	≈ 1.001153961 kg/m3
ounce (avoirdupois) per cubic inch	oz/in3	≡ oz/in3	≈ 1.729994044×103 kg/m3
ounce (avoirdupois) per gallon (imperial)	oz/gal	≡ oz/gal	≈ 6.236023291 kg/m3
ounce (avoirdupois) per gallon (US fluid)	oz/gal	≡ oz/gal	≈ 7.489151707 kg/m3
pound (avoirdupois) per cubic foot	lb/ft3	≡ lb/ft3	≈ 16.01846337 kg/m3
pound (avoirdupois) per cubic inch	lb/in3	≡ lb/in3	≈ 2.767990471×104 kg/m3
pound (avoirdupois) per gallon (imperial)	lb/gal	≡ lb/gal	≈ 99.77637266 kg/m3
pound (avoirdupois) per gallon (US fluid)	lb/gal	≡ lb/gal	≈ 119.8264273 kg/m3
slug per cubic foot	slug/ft3	≡ slug/ft3	≈ 515.3788184 kg/m3

Time

Time

Name of unit	Symbol	Definition	Relation to SI units
atomic unit of time	au	≡ a0/(α·c)	≈ 2.418 884 254×10−17 s
Callippic cycle		≡ 441 mo (hollow) + 499 mo (full) = 76 a of 365.25 d	= 2.398 3776×109 s
century	c	≡ 100 a (see below for definition of year length)	= 100 years
day	d	= 24 h	= 1440 min = 86400 s
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)	≈ 86 164.1 s
decade	dec	≡ 10 a (see below for definition of year length)	= 10 years
fortnight	fn	≡ 2 wk	= 1 209 600 s
helek		≡ 1/1 080 h	= 3.3 s
Hipparchic cycle		≡ 4 Callippic cycles - 1 d	= 9.593 424×109 s
hour	h	≡ 60 min	= 3 600 s
jiffy	j	≡ 1/60 s	= .016 s
jiffy (alternate)	ja	≡ 1/100 s	= 10 ms
ke (quarter of an hour)		≡ ¼ h = 1/96 d	= 60 × 60 / 4 s = 900 s = 60 / 4 min = 15 min
ke (traditional)		≡ 1/100 d	= 24 × 60 × 60 / 100 s = 864 s = 24 * 60 / 100 min = 14.4 min
lustre; lustrum		≡ 5 a of 365 d	= 1.5768×108 s
Metonic cycle; enneadecaeteris		≡ 110 mo (hollow) + 125 mo (full) = 6940 d ≈ 19 a	= 5.996 16×108 s
millennium		≡ 1 000 a (see below for definition of year length)	= 1000 years
milliday	md	≡ 1/1 000 d	= 24 × 60 × 60 / 1 000 s = 86.4 s
minute	min	≡ 60 s, due to leap seconds sometimes 59 s or 61 s,	= 60 s
moment		≡ 90 s	= 90 s
month (full)	mo	≡ 30 d	= 2 592 000 s
month (Greg. av.)	mo	Average Gregorian month = 1 a (Gregorian average) / 12 = 365.242 5 d / 12 = 30.436 875 d	≈ 2.6297×106 s
month (hollow)	mo	≡ 29 d	= 2 505 600 s
month (synodic)	mo	Cycle time of moon phases ≈ 29.530 589 d (Average)	≈ 2.551×106 s
octaeteris		= 48 mo (full) + 48 mo (hollow) + 3 mo (full) = 8 a of 365.25 d = 2922 d	= 2.524 608×108 s
Planck time		≡ (Gℏ/c5)½	≈ 1.351 211 868×10−43 s
second	s	time of 9 192 631 770 periods of the radiation corresponding to the transition between the 2 hyperfine levels of the ground state of the caesium 133 atom at 0 K (but other seconds are sometimes used in astronomy). Also that time it takes for light to travel a distance of 299,792,458 meters.	(SI base unit)
shake		≡ 10−8 s	= 10 ns
sigma		≡ 10−6 s	= 1 μs
Sothic cycle		≡ 1 461 a of 365 d	= 4.607 4096×1010 s
svedberg	S	≡ 10−13 s	= 100 fs
week	wk	≡ 7 d	= 168 h = 10 080 min = 604 800 s
year (common)	a, y, or yr	365 d	= 31 536 000 s
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.	= 31 556 952 s
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	= 31 557 600 s
year (leap)	a, y, or yr	366 d	= 31 622 400 s
year (mean tropical)	a, y, or yr	Conceptually, length of time it takes for the Sun to return to the same position in the cycle of seasons	≈ 365.24219 d, each day being 86,400 SI seconds ≈ 31 556 925 s
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	≈ 365.256 363 d ≈ 31 558 149.7632 s
Where UTC is observed, the length of time units longer than 1 s may increase or decrease by 1 s if a leap second occurs during the time interval of interest.

Frequency

Frequency

Name of unit	Symbol	Definition	Relation to SI units
hertz (SI unit)	Hz	≡ Number of cycles per second	= 1 Hz = 1/s
revolutions per minute	rpm	≡ One unit rpm equals one rotation completed around a fixed axis in one minute of time.	≈ 0.104719755 rad/s

Speed or velocity

Speed

Name of unit	Symbol	Definition	Relation to SI units
foot per hour	fph	≡ 1 ft/h	≈ 8.466 667×10−5 m/s
foot per minute	fpm	≡ 1 ft/min	= 5.08×10−3 m/s
foot per second	fps	≡ 1 ft/s	= 3.048×10−1 m/s
furlong per fortnight		≡ furlong/fortnight	≈ 1.663 095×10−4 m/s
inch per hour	iph	≡ 1 in/hr	≈ 7.05 556×10−6 m/s
inch per minute	ipm	≡ 1 in/min	≈ 4.23 333×10−4 m/s
inch per second	ips	≡ 1 in/s	= 2.54×10−2 m/s
kilometre per hour	km/h	≡ 1 km/h	= 1/3.6 m/s ≈ 2.777 778×10−1 m/s
knot	kn	≡ 1 nmi/h = 1.852 km/h	≈ 0.514 444 m/s
knot (Admiralty)	kn	≡ 1 NM (Adm)/h = 1.853 184 km/h	= 0.514 773 m/s
mach number	M	Ratio of the speed to the speed of sound in the medium. Varies especially with temperature. About 1225 km/h (761 mph) in air at sea level to about 1062 km/h (660 mph) at jet altitudes (12,200 metres (40,000 ft)). Unitless	≈ 340 to 295 m/s for aircraft
metre per second (SI unit)	m/s	≡ 1 m/s	= 1 m/s
mile per hour	mph	≡ 1 mi/h	= 0.447 04 m/s
mile per minute	mpm	≡ 1 mi/min	= 26.8224 m/s
mile per second	mps	≡ 1 mi/s	= 1 609.344 m/s
speed of light in vacuum	c	≡ 299 792 458 m/s	= 299 792 458 m/s
speed of sound in air	s	Varies especially with temperature. About 1225 km/h (761 mph) in air at sea level to about 1062 km/h (660 mph) at jet altitudes.	≈ 340 to 295 m/s at aircraft altitudes

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	CFM	≡ 1 ft3/min	= 4.719474432×10−4 m3/s
cubic foot per second	ft3/s	≡ 1 ft3/s	= 0.028316846592 m3/s
cubic inch per minute	in3/min	≡ 1 in3/min	= 2.7311773×10−7 m3/s
cubic inch per second	in3/s	≡ 1 in3/s	= 1.6387064×10−5 m3/s
cubic metre per second (SI unit)	m3/s	≡ 1 m3/s	= 1 m3/s
gallon (US fluid) per day	GPD	≡ 1 gal/d	= 4.381263638×10−8 m3/s
gallon (US fluid) per hour	GPH	≡ 1 gal/h	= 1.051503273×10−6 m3/s
gallon (US fluid) per minute	GPM	≡ 1 gal/min	= 6.30901964×10−5 m3/s
litre per minute	LPM	≡ 1 L/min	= 1.6×10−5 m3/s

Acceleration

Acceleration

Name of unit	Symbol	Definition	Relation to SI units
foot per hour per second	fph/s	≡ 1 ft/(h·s)	≈ 8.466 667×10−5 m/s2
foot per minute per second	fpm/s	≡ 1 ft/(min·s)	= 5.08×10−3 m/s2
foot per second squared	fps2	≡ 1 ft/s2	= 3.048×10−1 m/s2
gal; galileo	Gal	≡ 1 cm/s2	= 10−2 m/s2
inch per minute per second	ipm/s	≡ 1 in/(min·s)	≈ 4.233 333×10−4 m/s2
inch per second squared	ips2	≡ 1 in/s2	= 2.54×10−2 m/s2
knot per second	kn/s	≡ 1 kn/s	≈ 5.144 444×10−1 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)	= 4.4704×10−1 m/s2
mile per minute per second	mpm/s	≡ 1 mi/(min·s)	= 26.8224 m/s2
mile per second squared	mps2	≡ 1 mi/s2	= 1.609 344×103 m/s2
standard gravity	g	≡ 9.806 65 m/s2	= 9.806 65 m/s2

Force

Force

Name of unit	Symbol	Definition	Relation to SI units
atomic unit of force		≡ me·α2·c2/a0	≈ 8.238 722 06×10−8 N
dyne (cgs unit)	dyn	≡ g·cm/s2	= 10−5 N
kilogram-force; kilopond; grave-force	kgf; kp; Gf	≡ g × 1 kg	= 9.806 65 N
kip; kip-force	kip; kipf; klbf	≡ g × 1 000 lb	= 4.448 221 615 2605×103 N
milligrave-force, gravet-force	mGf; gf	≡ g × 1 g	= 9.806 65 mN
newton (SI unit)	N	A force capable of giving a mass of one kg an acceleration of one metre per second, per second.	= 1 N = 1 kg·m/s2
ounce-force	ozf	≡ g × 1 oz	= 0.278 013 850 953 781 25 N
pound-force	lbf	≡ g × 1 lb	= 4.448 221 615 2605 N
poundal	pdl	≡ 1 lb·ft/s2	= 0.138 254 954 376 N
sthene (mts unit)	sn	≡ 1 t·m/s2	= 1×103 N
ton-force	tnf	≡ g × 1 sh tn	= 8.896 443 230 521×103 N

See also: Conversion between weight (force) and mass

Pressure or mechanical stress

Pressure

Name of unit	Symbol	Definition	Relation to SI units
atmosphere (standard)	atm		≡ 101 325 Pa
atmosphere (technical)	at	≡ 1 kgf/cm2	= 9.806 65×104 Pa
bar	bar		≡ 105 Pa
barye (cgs unit)		≡ 1 dyn/cm2	= 0.1 Pa
centimetre of mercury	cmHg	≡ 13 595.1 kg/m3 × 1 cm × g	≈ 1.333 22×103 Pa
centimetre of water (4 °C)	cmH2O	≈ 999.972 kg/m3 × 1 cm × g	≈ 98.063 8 Pa
foot of mercury (conventional)	ftHg	≡ 13 595.1 kg/m3 × 1 ft × g	≈ 40.636 66×103 Pa
foot of water (39.2 °F)	ftH2O	≈ 999.972 kg/m3 × 1 ft × g	≈ 2.988 98×103 Pa
inch of mercury (conventional)	inHg	≡ 13 595.1 kg/m3 × 1 in × g	≈ 3.386 389×103 Pa
inch of water (39.2 °F)	inH2O	≈ 999.972 kg/m3 × 1 in × g	≈ 249.082 Pa
kilogram-force per square millimetre	kgf/mm2	≡ 1 kgf/mm2	= 9.806 65×106 Pa
kip per square inch	ksi	≡ 1 kipf/sq in	≈ 6.894 757×106 Pa
micron (micrometre) of mercury	$\mu$mHg	≡ 13 595.1 kg/m3 × 1 $\mu$m × g ≈ 0.001 torr	≈ 0.133 322 4 Pa
millimetre of mercury	mmHg	≡ 13 595.1 kg/m3 × 1 mm × g ≈ 1 torr	≈ 133.3224 Pa
millimetre of water (3.98 °C)	mmH2O	≈ 999.972 kg/m3 × 1 mm × g = 0.999 972 kgf/m2	= 9.806 38 Pa
pascal (SI unit)	Pa	≡ N/m2 = kg/(m·s2)	= 1 Pa
pièze (mts unit)	pz	≡ 1 000 kg/m·s2	= 1×103 Pa = 1 kPa
pound per square foot	psf	≡ 1 lbf/ft2	≈ 47.880 26 Pa
pound per square inch	psi	≡ 1 lbf/in2	≈ 6.894 757×103 Pa
poundal per square foot	pdl/sq ft	≡ 1 pdl/sq ft	≈ 1.488 164 Pa
short ton per square foot		≡ 1 sh tn × g / 1 sq ft	≈ 95.760 518×103 Pa
torr	torr	≡ 101 325/760 Pa	≈ 133.322 4 Pa

Torque or moment of force

Torque

Name of unit	Symbol	Definition	Relation to SI units
foot-pound force	ft lbf	≡ g × 1 lb × 1 ft	= 1.355 817 948 331 4004 N·m
foot-poundal	ft pdl	≡ 1 lb·ft2/s2	= 4.214 011 009 380 48×10−2 N·m
inch-pound force	in lbf	≡ g × 1 lb × 1 in	= 0.112 984 829 027 6167 N·m
metre kilogram	m kg	≡ N × m / g	≈ 0.101 971 621 N·m
Newton metre (SI unit)	N·m	≡ N × m = kg·m2/s2	= 1 N·m

Energy

Energy

Name of unit	Symbol	Definition	Relation to SI units
barrel of oil equivalent	boe	≈ 5.8×106 BTU59 °F	≈ 6.12×109 J
British thermal unit (ISO)	BTUISO	≡ 1.0545×103 J	= 1.0545×103 J
British thermal unit (International Table)	BTUIT		= 1.055 055 852 62×103 J
British thermal unit (mean)	BTUmean		≈ 1.055 87×103 J
British thermal unit (thermochemical)	BTUth		≈ 1.054 350×103 J
British thermal unit (39 °F)	BTU39 °F		≈ 1.059 67×103 J
British thermal unit (59 °F)	BTU59 °F	≡ 1.054 804×103 J	= 1.054 804×103 J
British thermal unit (60 °F)	BTU60 °F		≈ 1.054 68×103 J
British thermal unit (63 °F)	BTU63 °F		≈ 1.0546×103 J
calorie (International Table)	calIT	≡ 4.1868 J	= 4.1868 J
calorie (mean)	calmean	1⁄100 of the energy required to warm one gram of air-free water from 0 °C to 100 °C @ 1 atm	≈ 4.190 02 J
calorie (thermochemical)	calth	≡ 4.184 J	= 4.184 J
Calorie (US; FDA)	Cal	≡ 1 kcal	= 1000 cal = 4184 J
calorie (3.98 °C)	cal3.98 °C		≈ 4.2045 J
calorie (15 °C)	cal15 °C	≡ 4.1855 J	= 4.1855 J
calorie (20 °C)	cal20 °C		≈ 4.1819 J
Celsius heat unit (International Table)	CHUIT	≡ 1 BTUIT × 1 K/°R	= 1.899 100 534 716×103 J
cubic centimetre of atmosphere; standard cubic centimetre	cc atm; scc	≡ 1 atm × 1 cm3	= 0.101 325 J
cubic foot of atmosphere; standard cubic foot	cu ft atm; scf	≡ 1 atm × 1 ft3	= 2.869 204 480 9344×103 J
cubic foot of natural gas		≡ 1 000 BTUIT	= 1.055 055 852 62×106 J
cubic yard of atmosphere; standard cubic yard	cu yd atm; scy	≡ 1 atm × 1 yd3	= 77.468 520 985 2288×103 J
electronvolt	eV	≡ e × 1 V	≈ 1.602 177 33×10−19 ± 4.9×10−26 J
erg (cgs unit)	erg	≡ 1 g·cm2/s2	= 10−7 J
foot-pound force	ft lbf	≡ g × 1 lb × 1 ft	= 1.355 817 948 331 4004 J
foot-poundal	ft pdl	≡ 1 lb·ft2/s2	= 4.214 011 009 380 48×10−2 J
gallon-atmosphere (imperial)	imp gal atm	≡ 1 atm × 1 gal (imp)	= 460.632 569 25 J
gallon-atmosphere (US)	US gal atm	≡ 1 atm × 1 gal (US)	= 383.556 849 0138 J
hartree, atomic unit of energy	Eh	≡ me·α2·c2 (= 2 Ry)	≈ 4.359 744×10−18 J
horsepower-hour	hp·h	≡ 1 hp × 1 h	= 2.684 519 537 696 172 792×106 J
inch-pound force	in lbf	≡ g × 1 lb × 1 in	= 0.112 984 829 027 6167 J
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.	= 1 J = 1 m·N = 1 kg·m2/s2 = 1 C·V = 1 W·s
kilocalorie; large calorie	kcal; Cal	≡ 1 000 calIT	= 4.1868×103 J
kilowatt-hour; Board of Trade Unit	kW·h; B.O.T.U.	≡ 1 kW × 1 h	= 3.6×106 J
litre-atmosphere	l atm; sl	≡ 1 atm × 1 L	= 101.325 J
quad		≡ 1015 BTUIT	= 1.055 055 852 62×1018 J
rydberg	Ry	≡ R∞·ℎ·c	≈ 2.179 872×10−18 J
therm (E.C.)		≡ 100 000 BTUIT	= 105.505 585 262×106 J
therm (US)		≡ 100 000 BTU59 °F	= 105.4804×106 J
thermie	th	≡ 1 McalIT	= 4.1868×106 J
ton of coal equivalent	TCE	≡ 7 Gcalth	= 29.288×109 J
ton of oil equivalent	TOE	≡ 10 Gcalth	= 41.84×109 J
ton of TNT	tTNT	≡ 1 Gcalth	= 4.184×109 J

Power or heat flow rate

Power

Name of unit	Symbol	Definition	Relation to SI units
atmosphere-cubic centimetre per minute	atm ccm	≡ 1 atm × 1 cm3/min	= 1.688 75×10−3 W
atmosphere-cubic centimetre per second	atm ccs	≡ 1 atm × 1 cm3/s	= 0.101 325 W
atmosphere-cubic foot per hour	atm cfh	≡ 1 atm × 1 cu ft/h	= 0.797 001 244 704 W
atmosphere-cubic foot per minute	atm·cfm	≡ 1 atm × 1 cu ft/min	= 47.820 074 682 24 W
atmosphere-cubic foot per second	atm cfs	≡ 1 atm × 1 cu ft/s	= 2.869 204 480 9344×103 W
BTU (International Table) per hour	BTUIT/h	≡ 1 BTUIT/h	≈ 0.293 071 W
BTU (International Table) per minute	BTUIT/min	≡ 1 BTUIT/min	≈ 17.584 264 W
BTU (International Table) per second	BTUIT/s	≡ 1 BTUIT/s	= 1.055 055 852 62×103 W
calorie (International Table) per second	calIT/s	≡ 1 calIT/s	= 4.1868 W
erg per second	erg/s	≡ 1 erg/s	= 10−7 W
foot-pound-force per hour	ft lbf/h	≡ 1 ft lbf/h	≈ 3.766 161×10−4 W
foot-pound-force per minute	ft lbf/min	≡ 1 ft lbf/min	= 2.259 696 580 552 334×10−2 W
foot-pound-force per second	ft lbf/s	≡ 1 ft lbf/s	= 1.355 817 948 331 4004 W
horsepower (boiler)	bhp	≈ 34.5 lb/h × 970.3 BTUIT/lb	≈ 9.810 657×103 W
horsepower (European electrical)	hp	≡ 75 kp·m/s	= 736 W
horsepower (imperial electrical)	hp	≡ 746 W	= 746 W
horsepower (imperial mechanical)	hp	≡ 550 ft lbf/s	= 745.699 871 582 270 22 W
horsepower (metric)	hp	≡ 75 m kgf/s	= 735.498 75 W
litre-atmosphere per minute	L·atm/min	≡ 1 atm × 1 L/min	= 1.688 75 W
litre-atmosphere per second	L·atm/s	≡ 1 atm × 1 L/s	= 101.325 W
lusec	lusec	≡ 1 L·µmHg/s	≈ 1.333×10−4 W
poncelet	p	≡ 100 m kgf/s	= 980.665 W
square foot equivalent direct radiation	sq ft EDR	≡ 240 BTUIT/h	≈ 70.337 057 W
ton of air conditioning		≡ 2000 lbs of ice melted / 24 h	≈ 3 504 W
ton of refrigeration (imperial)		≡ 2240 lb × iceIT / 24 h: iceIT = 144°F × 2326 J/kg.°F	≈ 3.938 875×103 W
ton of refrigeration (IT)		≡ 200 lbs × iceIT / 24 h: iceIT = 144° × 2326 J/kg.°F	≈ 3.516 853×103 W
watt (SI unit)	W	The power which in one second of time gives rise to one joule of energy.	= 1 W = 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	≡ ℏ ≡ ℎ/2π	≈ 1.054 571 68×10−34 J·s

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)	≈ 4.133 789×10−4 Pa·s
pound per foot second	lb/(ft·s)	≡ 1 lb/(ft·s)	≈ 1.488164 Pa·s
pound-force second per square foot	lbf·s/ft2	≡ 1 lbf·s/ft2	≈ 47.88026 Pa·s
pound-force second per square inch	lbf·s/in2	≡ 1 lbf·s/in2	≈ 6,894.757 Pa·s

Kinematic viscosity

Kinematic viscosity

Name of unit	Symbol	Definition	Relation to SI units
square foot per second	ft2/s	≡ 1 ft2/s	= 0.09290304 m2/s
square metre per second (SI unit)	m2/s	≡ 1 m2/s	= 1 m2/s
stokes (cgs unit)	St	≡ 10−4 m2/s	= 10−4 m2/s

Electric current

Electric current

Name of unit	Symbol	Definition	Relation to SI units
ampere (SI base unit)	A	≡ The constant current needed to produce a force of 2 ×10−7 newton per metre between two straight parallel conductors of infinite length and negligible circular cross-section placed one metre apart in a vacuum.	= 1 A = 1 C/s
electromagnetic unit; abampere (cgs unit)	abamp	≡ 10 A	= 10 A
esu per second; statampere (cgs unit)	esu/s	≡ (0.1 A·m/s) / c	≈ 3.335641×10−10 A

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	≈ 1.602 176 462×10−19 C
coulomb	C	≡ The amount of electricity carried in one second of time by one ampere of current.	= 1 C = 1 A·s
faraday	F	≡ 1 mol × NA·e	≈ 96 485.3383 C
milliampere hour	mA·h	≡ 0.001 A × 1 h	= 3.6 C
statcoulomb; franklin; electrostatic unit (cgs unit)	statC; Fr; esu	≡ (0.1 A·m) / c	≈ 3.335 641×10−10 C

Electric dipole

Electric dipole

Name of unit	Symbol	Definition	Relation to SI units
atomic unit of electric dipole moment	ea0		≈ 8.478 352 81×10−30 C·m
coulomb meter	C·m		= 1 C · 1 m
debye	D	= 10−10 esu·Å	= 3.33564095×10−30 C·m

Electromotive force, electric potential difference

Voltage, electromotive force

Name of unit	Symbol	Definition	Relation to SI units
abvolt (cgs unit)	abV	≡ 1×10−8 V	= 1×10−8 V
statvolt (cgs unit)	statV	≡ c· (1 μJ/A·m)	= 299.792 458 V
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.	= 1 V = 1 W/A = 1 kg·m2/(A·s3)

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.	= 1 Ω = 1 V/A = 1 kg·m2/(A2·s3)

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.	= 1 F = 1 C/V = 1 A2·s4/(kg·m2)

Magnetic flux

magnetic flux

Name of unit	Symbol	Definition	Relation to SI units
maxwell (CGS unit)	Mx	≡ 10−8 Wb	= 1×10−8 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.	= 1 Wb = 1 V·s = 1 kg·m2/(A·s2)

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	= 1×10−4 T
tesla (SI unit)	T	≡ Wb/m2	= 1 T = 1 Wb/m2 = 1 kg/(A·s2)

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.	= 1 H = 1 Wb/A = 1 kg·m2/(A·s)2

Temperature

Further information: Conversion of units of temperature

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] × 2/3
degree Fahrenheit	°F	°F ≡ °C × 9/5 + 32	[K] ≡ ([°F] + 459.67) × 5/9
degree Newton	°N		[K] = [°N] × 100/33 + 273.15
degree Rankine	°R;	°R ≡ K × 9/5	[K] ≡ [°R] × 5/9
degree Réaumur	°Ré		[K] = [°Ré] × 5/4 + 273.15
degree Rømer	°Rø		[K] = ([°Rø] − 7.5) × 40/21 + 273.15
Regulo Gas Mark	GM;	°F ≡ GM × 25 + 300	[K] ≡ [GM] × 125/9 + 422.038
kelvin (SI base unit)	K	≡ 1/273.16 of the thermodynamic temperature of the triple point of water.	≡ 1 K

Information entropy

Information entropy

Name of unit	Symbol	Definition	Relation to SI units	Relation to bits
SI unit	J/K	≡ J/K	= 1 J/K
nat; nip; nepit	nat	≡ kB	= 1.380 650 5(23)×10−23 J/K
bit; shannon	bit; b; Sh	≡ ln(2) × kB	= 9.569 940 (16)×10−24 J/K	= 1 bit
ban; hartley	ban; Hart	≡ ln(10) × kB	= 3.179 065 3(53)×10−23 J/K
nibble		≡ 4 bits	= 3.827 976 0(64)×10−23 J/K	= 22 bit
byte	B	≡ 8 bits	= 7.655 952 (13)×10−23 J/K	= 23 bit
kilobyte (decimal)	kB	≡ 1 000 B	= 7.655 952 (13)×10−20 J/K	= 8×103 bit = 8000 bit
kilobyte (kibibyte)	KB; KiB	≡ 1 024 B	= 7.839 695 (13)×10−20 J/K	= 213 bit = 8192 bit

Often, information entropy is measured in shannons, 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. Other times the bit is used as a measure of information entropy and is thus a synonym of shannon.

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); candle	cd	The luminous intensity, in a given direction, of a source that emits monochromatic radiation of frequency 540×1012 hertz and that has a radiant intensity in that direction of 1/683 watt per steradian.	= 1 cd
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. Approximately 0.981 cd.	≈ 0.981 cd

Luminance

Luminance

Name of unit	Symbol	Definition	Relation to SI units
candela per square foot	cd/ft2	≡ cd/ft2	≈ 10.763910417 cd/m2
candela per square inch	cd/in2	≡ cd/in2	≈ 1,550.0031 cd/m2
candela per square metre (SI unit); nit (deprecated)	cd/m2	≡ cd/m2	= 1 cd/m2
footlambert	fL	≡ (1/π) cd/ft2	≈ 3.4262590996 cd/m2
lambert	L	≡ (104/π) cd/m2	≈ 3,183.0988618 cd/m2
stilb (CGS unit)	sb	≡ 104 cd/m2	≈ 1×104 cd/m2

Luminous flux

Luminous flux

Name of unit	Symbol	Definition	Relation to SI units
lumen (SI unit)	lm	≡ cd·sr	= 1 lm = 1 cd·sr

Illuminance

Illuminance

Name of unit	Symbol	Definition	Relation to SI units
footcandle; lumen per square foot	fc	≡ lm/ft2	= 10.763910417 lx
lumen per square inch	lm/in2	≡ lm/in2	≈ 1,550.0031 lx
lux (SI unit)	lx	≡ lm/m2	= 1 lx = 1 lm/m2
phot (CGS unit)	ph	≡ lm/cm2	= 1×104 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	≡ 3.7×1010 Bq	= 3.7×1010 Bq
rutherford (H)	rd	≡ 1 MBq	= 1×106 Bq

Please note that although becquerel (Bq) and hertz (Hz) both ultimately refer to the same SI base unit (s⁻¹), Hz is used only for periodic phenomena, and Bq is only used for stochastic processes associated with radioactivity.

Radiation - exposure

Radiation - exposure

Name of unit	Symbol	Definition	Relation to SI units
roentgen	R	1 R ≡ 2.58×10−4 C/kg	= 2.58×10−4 C/kg

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

Radiation - absorbed dose

Radiation - absorbed dose

Name of unit	Symbol	Definition	Relation to SI units
gray (SI unit)	Gy	≡ 1 J/kg = 1 m2/s2	= 1 Gy
rad	rad	≡ 0.01 Gy	= 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	= 1 Sv

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 = Q · D

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.

Software tools

Home and office computers come with converters in bundled spreadsheet applications or can access free converters via the Internet. Units and measurements can be easily converted using these tools, but only if the units are explicitly defined and the conversion is compatible (e.g., cmHg to kPa).

General commercial sources of converters

• Advanced electronic calculators have unit-conversion functionality.
• Spreadsheet programs usually provide conversion functions or formulas or the user can write their own.
• Commercial mathematical, scientific and technical applications often include converters.

See also

• Accuracy and precision
• Conversion of units of temperature
• English units
• False precision
• Imperial units
• International System of Units
• Mesures usuelles
• Metric prefix (e.g. "kilo-" prefix)

• Metric system
• Natural units
• Rounding
• Significant figures
• United States customary units
• Units (software)
• Units conversion by factor-label
• Units of measurement

Notes and references

Notes

External links

• Statutory Instrument 1995 No. 1804 Units of measurement regulations 1995 From legislation.gov.uk
• How Many? A dictionary of units of measurement
• Template:PDFlink
• NIST Guide to SI Units Many conversion factors listed.
• The Unified Code for Units of Measure
• Units, Symbols, and Conversions XML Dictionary
• Template:Dmoz
• Template:Dmoz