Pgina modificada da Wikipedia: Converso de unidades.

 

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:

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 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
ngstrm 110−10
 m
≡ 0.1 nm
astronomical unit AU ≈ Distance from Earth to Sun ≈ 149597871464 m [1]
barleycorn (H)   = ⅓ in (see note above about rounding) ≈ 8.4610−3 m
bohr, atomic unit of length a0 Bohr radius of hydrogen 5.291772085910−11
  3.610−20
 m
[2]
cable length (Imperial)   ≡ 608 ft ≈ 185.3184 m
cable length (International)   ≡ 1/10 nmi ≡ 185.2 m
cable length (U.S.)   ≡ 720 ft = 219.456 m
chain (Gunter's; Surveyor's) ch ≡ 66 ft(US) ≡ 4 rods [3] 20.11684 m
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 fm ≡ 6 ft [4] = 1.8288 m
fermi fm 110−15
 m
[4]
110−15
 m
finger   ≡ 7/8 in = 0.022225 m
finger (cloth)   ≡ 4 in = 0.1143 m
foot (Benot) (H) ft (Ben) 0.304799735 m
foot (Clarke's; Cape) (H) ft (Cla) 0.3047972654 m
foot (Indian) (H) ft Ind 0.304799514 m
foot (International) ft ≡ 1/3 yd ≡ 0.3048 m ≡ 12 inches ≡ 0.3048 m
foot (Sear's) (H) ft (Sear) 0.30479947 m
foot (U.S. Survey) ft (US) 12003937 m [5] 0.304800610 m
french; charriere F 13 mm = 0.3 10−3 m
furlong fur ≡ 10 chains = 660 ft = 220 yd [4] = 201.168 m
hand   ≡ 4 in [4] ≡ 0.1016 m
inch (International) in ≡ 1/36 yd ≡ 1/12 ft ≡ 0.0254 m
league (land) lea ≡ 3 US Statute miles [3] = 4828.032 m
light-day   ≡ 24 light-hours 2.590206837121013
 m
light-hour   ≡ 60 light-minutes 1.07925284881012
 m
light-minute   ≡ 60 light-seconds 1.7987547481010
 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 [6] = 9.46073047258081015
 m
line ln ≡ 1/12 in [7] = 0.002116 m
link (Gunter's; Surveyor's) lnk ≡ 1/100 ch [4] ≡ 0.66 ft ≡ 7.92in = 0.201168 m
link (Ramsden's; Engineer's) lnk ≡ 1 ft [4] = 0.3048 m
metre (SI base unit) m ≡ Distance light travels in 1299792458 of a second in vacuum.[8]
110000000 of the distance from equator to pole.
≡ 1 m
mickey   1200 in = 1.2710−4
 m
micron 110−6
 m
mil; thou mil 110−3
 in
2.5410−5
 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 (U.S. Survey) mi 5280 US Survey feet ≡ (5280 12003937) m ≈ 1609.347219 m
nail (cloth)   ≡ 2 in [4] = 0.057 15 m
nanometer nm 110−9
 m
110−9
 m
nautical league NL; nl ≡ 3 nmi [4] = 5556 m
nautical mile (Admiralty) NM (Adm); nmi (Adm) = 6080 ft = 1853.184 m
nautical mile (international) NM; nmi 1852 m [9] 1852 m
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 Distance of star with parallax shift of one arc second from a base of one astronomical unit 3.085 677 821016 6106 m [10]
pica   ≡ 12 points Dependent on point measures.
point (American, English) [11][12] pt ≡ 1/72.272 in 0.000 351 450 m
point (Didot; European) [12][13] pt ≡ 1/12 1/72 of pied du roi;

After 1878:
≡ 5/133 cm
0.000 375 97 m;

After 1878:
0.000 375 939 85 m
point (PostScript) [11] pt ≡ 1/72 in = 0.000 352 7 m
point (TeX) [11] pt ≡ 1/72.27 in = 0.000 351 4598 m
quarter   ≡ yd = 0.2286 m
rod; pole; perch (H) rd ≡ 16 ft = 5.0292 m
rope (H) rope ≡ 20 ft [4] = 6.096 m
span (H)   ≡ 9 in [4] = 0.2286 m
spat [14] ≡ 11012 m
stick (H)   ≡ 2 in = 0.0508 m
stigma; bicron (picometre) pm ≡ 110−12 m
twip twp 1/1440 in = 1.763810−5 m
x unit; siegbahn xu ≈ 1.002110−13 m [4]
yard (International) yd ≡ 0.9144 m [5] ≡ 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 [15]
are a ≡ 100 m2 = 100 m2
barn b ≡ 10−28 m2 = 10−28 m2
barony   4000 ac 1.618 742107 m2
board bd ≡ 1 in 1 ft = 7.741 9210−3 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 07510−4 m2
circular mil; circular thou circ mil ≡ π/4 mil2 5.067 07510−10 m2
cord   ≡ 192 bd = 1.486 448 64 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) 5105 m2
rood ro ≡ ac = 1 011.714 1056 m2
section ≡ 1 mi 1 mi = 2.589 988 110 336106 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 (U.S. 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 30410−2 m2
square foot (U.S. Survey) sq ft ≡ 1 ft (US) 1 ft (US) 9.290 341 161 327 4910−2 m2
square inch sq in ≡ 1 in 1 in ≡ 6.451610−4 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 422410−2 m2
square link (Gunter's)(US Survey) sq lnk ≡ 1 lnk 1 lnk ≡ 0.66 ft(US) 0.66 ft(US) 4.046 87210−2 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 = 6.451610−10 m2
square mile sq mi ≡ 1 mi 1 mi = 2.589 988 110 336106 m2
square mile (U.S. Survey) sq mi ≡ 1 mi (US) 1 mi (US) 2.589 998 47106 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 994107 m2
yardland   ≈ 30 ac 1.2105 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 (U.S. dry) bl (US) ≡ 105 qt (US) = 105/32 bu (US lvl) = 0.115 628 198 985 075 m3
barrel (U.S. fluid) fl bl (US) ≡ 31 gal (US) = 0.119 240 471 196 m3
board-foot fbm ≡ 144 cu in 2.359 737 21610−3 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 (U.S. dry heaped) bu (US) ≡ 1 bu (US lvl) = 0.044 048 837 7086 m3
bushel (U.S. 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 06410−6 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 62510−6 m3
cup (Canadian) c (CA) ≡ 8 fl oz (Imp) = 227.304510−6 m3
cup (metric) c ≡ 250.010−6 m3 = 250.010−6 m3
cup (U.S. customary) c (US) ≡ 8 US fl oz ≡ 1/16 gal (US) = 236.588 236510−6 m3
cup (U.S. food nutrition labeling) c (US) ≡ 240 mL[16] = 2.410−4
 m3
dash (Imperial)   ≡ 1/384 gi (Imp) = pinch (Imp) = 369.961 751 302 08 310−9 m3
dash (U.S.)   ≡ 1/96 US fl oz = US pinch = 308.057 599 609 37510−9 m3
dessertspoon (Imperial)   ≡ 1/12 gi (Imp) = 11.838 776 041610−6 m3
drop (Imperial) gtt ≡ 1/288 fl oz (Imp) = 98.656 467 013 810−9 m3
drop (Imperial) (alt) gtt 1/1 824 gi (Imp) 77.886 68410−9 m3
drop (medical)   ≡ 1/12 ml = 83.0310−9 m3
drop (metric)   ≡ 1/20 mL = 50.010−9 m3
drop (U.S.) gtt ≡ 1/360 US fl oz = 82.148 693 2291610−9 m3
drop (U.S.) (alt) gtt ≡ 1/456 US fl oz 64.854 23110−9 m3
fifth   ≡ 1/5 US gal = 757.082 356810−6 m3
firkin   ≡ 9 gal (US) = 0.034 068 706 056 m3
fluid drachm (Imperial) fl dr ≡ ⅛ fl oz (Imp) = 3.551 632 812510−6 m3
fluid dram (U.S.); U.S. fluidram fl dr ≡ ⅛ US fl oz = 3.696 691 195 312510−6 m3
fluid scruple (Imperial) fl s ≡ 1/24 fl oz (Imp) = 1.183 877 6041610−6 m3
gallon (beer) beer gal ≡ 282 cu in = 4.621 152 04810−3 m3
gallon (Imperial) gal (Imp) 4.546  09 L 4.546 0910−3 m3
gallon (U.S. dry) gal (US) ≡ ⅛ bu (US lvl) = 4.404 883 770 8610−3 m3
gallon (U.S. fluid; Wine) gal (US) ≡ 231 cu in 3.785 411 78410−3 m3
gill (Imperial); Noggin gi (Imp); nog ≡ 5 fl oz (Imp) = 142.065 312510−6 m3
gill (U.S.) gi (US) ≡ 4 US fl oz = 118.294 118 2510−6 m3
hogshead (Imperial) hhd (Imp) ≡ 2 bl (Imp) = 0.327 318 48 m3
hogshead (U.S.) hhd (US) ≡ 2 fl bl (US) = 0.238 480 942 392 m3
jigger (bartending)   ≡ 1 US fl oz ≈ 44.3610−6 m3
kilderkin   ≡ 18 gal (Imp) = 0.081 829 62 m3
lambda λ ≡ 1 mm3 = 110−9 m3
last   ≡ 80 bu (Imp) = 2.909 4976 m3
litre L ≡ 1 dm3 [17] ≡ 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) = 59.193 880 208 310−9 m3
minim (U.S.) min ≡ 1/480 US fl oz = 1/60 US fl dr = 61.611 519 921 87510−9 m3
ounce (fluid Imperial) fl oz (Imp) ≡ 1/160 gal (Imp) 28.413 062510−6 m3
ounce (fluid U.S. customary) US fl oz ≡ 1/128 gal (US) 29.573 529 562510−6 m3
ounce (fluid U.S. food nutrition labeling) US fl oz ≡ 30 mL[16] 310−5
 m3
peck (Imperial) pk ≡ 2 gal (Imp) = 9.092 1810−3 m3
peck (U.S. dry) pk ≡ US lvl bu = 8.809 767 541 7210−3 m3
perch per ≡ 16 ft 1 ft 1 ft = 0.700 841 953 152 m3
pinch (Imperial)   ≡ 1/192 gi (Imp) = ⅛ tsp (Imp) = 739.923 502 6041610−9 m3
pinch (U.S.)   ≡ 1/48 US fl oz = ⅛ US tsp = 616.115 199 218 7510−9 m3
pint (Imperial) pt (Imp) ≡ ⅛ gal (Imp) = 568.261 2510−6 m3
pint (U.S. dry) pt (US dry) ≡ 1/64 bu (US lvl) ≡ ⅛ gal (US dry) = 550.610 471 357510−6 m3
pint (U.S. fluid) pt (US fl) ≡ ⅛ gal (US) = 473.176 47310−6 m3
pony   ≡ 3/4 US fl oz = 22.180 147 171 87510−6 m3
pottle; quartern   ≡ gal (Imp) = 80 fl oz (Imp) = 2.273 04510−3 m3
quart (Imperial) qt (Imp) ≡ gal (Imp) = 1.136 522510−3 m3
quart (U.S. dry) qt (US) ≡ 1/32 bu (US lvl) = gal (US dry) = 1.101 220 942 71510−3 m3
quart (U.S. fluid) qt (US) ≡ gal (US fl) = 946.352 94610−6 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 (U.S.)   ≡ 3 bu (US lvl) = 0.105 717 210 500 64 m3
seam   ≡ 8 bu (US lvl) = 0.281 912 561 335 04 m3
shot   ≡ 1 US fl oz ≈ 29.5710−6 m3
strike (Imperial)   ≡ 2 bu (Imp) = 0.072 737 44 m3
strike (U.S.)   ≡ 2 bu (US lvl) = 0.070 478 140 333 76 m3
tablespoon (Australian metric)   ≡ 20.010−6 m3
tablespoon (Canadian) tbsp ≡ fl oz (Imp) = 14.206 531 2510−6 m3
tablespoon (Imperial) tbsp ≡ 5/8 fl oz (Imp) = 17.758 164 062510−6 m3
tablespoon (metric)   ≡ 15.010−6 m3
tablespoon (U.S. customary) tbsp ≡ US fl oz = 14.786 764 782510−6 m3
tablespoon (U.S. food nutrition labeling) tbsp ≡ 15 mL[16] = 1.510−5
 m3
teaspoon (Canadian) tsp ≡ 1/6 fl oz (Imp) = 4.735 510 41610−6 m3
teaspoon (Imperial) tsp ≡ 1/24 gi (Imp) = 5.919 388 0208310−6 m3
teaspoon (metric)   ≡ 5.010−6 m3 = 5.010−6 m3
teaspoon (U.S. customary) tsp ≡ 1/6 US fl oz = 4.928 921 59510−6 m3
teaspoon (U.S. food nutrition labeling) tsp ≡ 5 mL[16] = 510−6
 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 (U.S.)   ≡ 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 2π/6400 rad 0.981 74810−3 rad
arcminute; moa ' ≡ 1/60 0.290 88810−3 rad
arcsecond " 1/3600 4.848 13710−6 rad
centesimal minute of arc ' ≡ 1 grad/100 0.157 08010−3 rad
centesimal second of arc " 1 grad/(10 000) 1.570 79610−6 rad
degree (of arc) ≡ 1/360 of a revolution ≡ π/180 rad 17.453 29310−3 rad
grad; gradian; gon grad ≡ 1/400 of a revolution ≡ 2π/400 rad ≡ 0.9 ≈ 15.707 96310−3 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
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.[14] = 1 sr

Mass

Notes:

Mass
Name of unit Symbol Definition Relation to SI units
atomic mass unit, unified u; AMU 1.660 538 7310−27 1.310−36 kg
atomic unit of mass, electron rest mass me 9.109 382 1510−31 4510−39 kg [18]
bag (coffee)   ≡ 60 kg = 60 kg
bag (Portland cement)   ≡ 94 lb av = 42.637 682 78 kg
barge   ≡ 22 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 1010−27 1.310−36 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 = 1.782610−36 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
hyl (CGS unit)   ≡ 1 gee 1 g 1 s2/m = 9.806 65 g
hyl (MKS unit)   ≡ 1 gee 1 kg 1 s2/m = 9.806 65 kg
kilogram kg ≡ mass of the prototype near Paris (≈ mass of 1L of water) ≡ 1 kg (SI base unit)[8]
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 (U.S. food nutrition labeling) oz ≡ 28 g[16] = 28 g
pennyweight dwt; pwt ≡ 1/20 oz t = 1.555 173 84 g
point   ≡ 1/100 ct = 2 mg
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)   ≡ short tn = 226.796 185 kg
quarter, long (informal)   ≡ 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 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 [19] and.[14]

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 1.729994044103
 kg/m3
ounce (avoirdupois) per gallon (Imperial) oz/gal ≡ oz/gal 6.236023291 kg/m3
ounce (avoirdupois) per gallon (U.S. 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 2.767990471104
 kg/m3
pound (avoirdupois) per gallon (Imperial) lb/gal ≡ lb/gal 99.77637266 kg/m3
pound (avoirdupois) per gallon (U.S. fluid) lb/gal ≡ lb/gal 119.8264273 kg/m3
slug per cubic foot slug/ft3 ≡ slug/ft3 515.3788184 kg/m3

Time

Time, t
Name of unit Symbol Definition Relation to SI units
atomic unit of time au a0/(αc) 2.418 884 25410−17 s
Callippic cycle   ≡ 441 mo (hollow) + 499 mo (full) = 76 a of 365.25 d = 2.398 3776109 s
century c ≡ 100 a (see below for definition of year length) = 100 year
day d = 24 h = 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 year
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 424109 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)   ≡ 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 = 1.5768108 s
Metonic cycle; enneadecaeteris   ≡ 110 mo (hollow) + 125 mo (full) = 6940 d ≈ 19 a = 5.996 16108 s
millennium   1 000 a (see below for definition of year length) = 1000 year
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[20] = 2 592 000 s
month (Greg. av.) mo Average Gregorian month = 365.2425/12 d = 30.436875 d 2.6297106 s
month (hollow) mo ≡ 29 d[20] = 2 505 600 s
month (synodic) mo Cycle time of moon phases ≈ 29.530589 days (Average) 2.551106 s
octaeteris   = 48 mo (full) + 48 mo (hollow) + 3 mo (full)[21][22] = 8 a of 365.25 d = 2922 d = 2.524 608108 s
Planck time   ≡ (G/c5) 1.351 211 86810−43 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[8] (but other seconds are sometimes used in astronomy) (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 40961010 s
svedberg S ≡ 10−13 s = 100 fs
week wk ≡ 7 d = 604 800 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 (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
year (tropical) a, y, or yr ≡ Length of time it takes for the Sun to return to the same position in the cycle of seasons 365.242 190 d ≈ 31 556 925 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 66710−5 m/s
foot per minute fpm ≡ 1 ft/min = 5.0810−3 m/s
foot per second fps ≡ 1 ft/s = 3.04810−1 m/s
furlong per fortnight   ≡ furlong/fortnight 1.663 09510−4 m/s
inch per minute ipm ≡ 1 in/min 4.23 33310−4 m/s
inch per second ips ≡ 1 in/s = 2.5410−2 m/s
kilometre per hour km/h ≡ 1 km/h 2.777 77810−1 m/s
knot kn ≡ 1 NM/h = 1.852 km/h 0.514 444 m/s
knot (Admiralty) kn ≡ 1 NM (Adm)/h = 1.853 184 km/h[citation needed] = 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. 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 = 4.71947443210−4
 m3/s
cubic foot per second ft3/s ≡ 1 ft3/s = 0.028316846592 m3/s
cubic inch per minute in3/min ≡ 1 in3/min = 2.731177310−7 m3/s
cubic inch per second in3/s ≡ 1 in3/s = 1.638706410−5
 m3/s
cubic metre per second (SI unit) m3/s ≡ 1 m3/s = 1 m3/s
gallon (U.S. fluid) per day GPD ≡ 1 gal/d = 4.38126363810−8 m3/s
gallon (U.S. fluid) per hour GPH ≡ 1 gal/h = 1.05150327310−6 m3/s
gallon (U.S. fluid) per minute GPM ≡ 1 gal/min = 6.3090196410−5
 m3/s
litre per minute LPM ≡ 1 L/min = 1.610−5 m3/s

Acceleration

Acceleration
Name of unit Symbol Definition Relation to SI units
foot per hour per second fph/s ≡ 1 ft/(hs) 8.466 66710−5 m/s2
foot per minute per second fpm/s ≡ 1 ft/(mins) = 5.0810−3 m/s2
foot per second squared fps2 ≡ 1 ft/s2 = 3.04810−1 m/s2
gal; galileo Gal ≡ 1 cm/s2 = 10−2 m/s2
inch per minute per second ipm/s ≡ 1 in/(mins) 4.233 33310−4 m/s2
inch per second squared ips2 ≡ 1 in/s2 = 2.5410−2 m/s2
knot per second kn/s ≡ 1 kn/s 5.144 44410−1 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/(hs) = 4.470410−1 m/s2
mile per minute per second mpm/s ≡ 1 mi/(mins) = 26.8224 m/s2
mile per second squared mps2 ≡ 1 mi/s2 = 1.609 344103 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 ≡ meα2c2/a0 8.238 722 0610−8 N [23]
dyne (cgs unit) dyn ≡ gcm/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 2605103 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.[24] = 1 N = 1 kgm/s2
ounce-force ozf g 1 oz = 0.278 013 850 953 7812 N
pound lb ≡ slugft/s2 = 4.448 230 531 N
pound-force lbf g 1 lb = 4.448 221 615 2605 N
poundal pdl ≡ 1 lbft/s2 = 0.138 254 954 376 N
sthene (mts unit) sn ≡ 1 tm/s2 = 1103 N
ton-force tnf g 1 sh tn = 8.896 443 230 521103 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 [25]
atmosphere (technical) at ≡ 1 kgf/cm2 = 9.806 65104 Pa [25]
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 22103 Pa [25]
centimetre of water (4 C) cmH2O ≈ 999.972 kg/m3 1 cm g ≈ 98.063 8 Pa [25]
foot of mercury (conventional) ftHg 13 595.1 kg/m3 1 ft g 40.636 66103 Pa [25]
foot of water (39.2 F) ftH2O ≈ 999.972 kg/m3 1 ft g 2.988 98103 Pa [25]
inch of mercury (conventional) inHg 13 595.1 kg/m3 1 in g 3.386 389103 Pa [25]
inch of water (39.2 F) inH2O ≈ 999.972 kg/m3 1 in g ≈ 249.082 Pa [25]
kilogram-force per square millimetre kgf/mm2 ≡ 1 kgf/mm2 = 9.806 65106 Pa [25]
kip per square inch ksi ≡ 1 kipf/sq in 6.894 757106 Pa [25]
micron (micrometre) of mercury μmHg 13 595.1 kg/m3 1 μm g ≈ 0.001 torr 0.133 322 4 Pa [25]
millimetre of mercury mmHg 13 595.1 kg/m3 1 mm g ≈ 1 torr ≈ 133.3224 Pa [25]
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/(ms2) = 1 Pa [26]
pize (mts unit) pz 1 000 kg/ms2 = 1103 Pa = 1 kPa
pound per square foot psf ≡ 1 lbf/ft2 47.880 26 Pa [25]
pound per square inch psi ≡ 1 lbf/in2 6.894 757103 Pa [25]
poundal per square foot pdl/sq ft ≡ 1 pdl/sq ft 1.488 164 Pa [25]
short ton per square foot   ≡ 1 sh tn g / 1 sq ft 95.760 518103 Pa
torr torr 101 325/760 Pa ≈ 133.322 4 Pa [25]

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 Nm
foot-poundal ft pdl ≡ 1 lbft2/s2 = 4.214 011 009 380 4810−2 Nm
inch-pound force in lbf g 1 lb 1 in = 0.112 984 829 027 6167 Nm
metre kilogram m kg ≡ N m / g 0.101 971 621 Nm
Newton metre (SI unit) Nm ≡ N m = kgm2/s2 = 1 Nm

Energy, work, or amount of heat

Energy
Name of unit Symbol Definition Relation to SI units
barrel of oil equivalent bboe ≈ 5.8106 BTU59 F ≈ 6.12109 J
British thermal unit (ISO) BTUISO ≡ 1.0545103 J = 1.0545103 J
British thermal unit (International Table) BTUIT = 1.055 055 852 62103 J
British thermal unit (mean) BTUmean 1.055 87103 J
British thermal unit (thermochemical) BTUth 1.054 350103 J
British thermal unit (39 F) BTU39 F 1.059 67103 J
British thermal unit (59 F) BTU59 F 1.054 804103 J = 1.054 804103 J
British thermal unit (60 F) BTU60 F 1.054 68103 J
British thermal unit (63 F) BTU63 F ≈ 1.0546103 J
calorie (International Table) calIT ≡ 4.1868 J = 4.1868 J
calorie (mean) calmean 1100 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 (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 716103 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 9344103 J
cubic foot of natural gas   1 000 BTUIT = 1.055 055 852 62106 J
cubic yard of atmosphere; standard cubic yard cu yd atm; scy ≡ 1 atm 1 yd3 = 77.468 520 985 2288103 J
electronvolt eV e 1 V 1.602 177 3310−19 4.910−26 J
erg (cgs unit) erg ≡ 1 gcm2/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 lbft2/s2 = 4.214 011 009 380 4810−2 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 ≡ meα2c2 (= 2 Ry) 4.359 74410−18 J
horsepower-hour hph ≡ 1 hp 1 h = 2.684 519 537 696 172 792106 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.[24] = 1 J = 1 mN = 1 kgm2/s2 = 1 CV = 1 Ws
kilocalorie; large calorie kcal; Cal 1 000 calIT = 4.1868103 J
kilowatt-hour; Board of Trade Unit kWh; B.O.T.U. ≡ 1 kW 1 h = 3.6106 J
litre-atmosphere l atm; sl ≡ 1 atm 1 L = 101.325 J
quad   ≡ 1015 BTUIT = 1.055 055 852 621018 J
rydberg Ry Rc 2.179 87210−18 J
therm (E.C.)   100 000 BTUIT = 105.505 585 262106 J
therm (U.S.)   100 000 BTU59 F = 105.4804106 J
thermie th ≡ 1 McalIT = 4.1868106 J
ton of coal equivalent TCE ≡ 7 Gcalth = 29.3076109 J
ton of oil equivalent TOE ≡ 10 Gcalth = 41.868109 J
ton of TNT tTNT ≡ 1 Gcalth = 4.184109 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 7510−3 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 atmcfm ≡ 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 9344103 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 62103 W
calorie (International Table) per second calIT/s ≡ 1 calIT/s = 4.1868 W
foot-pound-force per hour ft lbf/h ≡ 1 ft lbf/h 3.766 16110−4 W
foot-pound-force per minute ft lbf/min ≡ 1 ft lbf/min = 2.259 696 580 552 33410−2 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 657103 W
horsepower (European electrical) hp ≡ 75 kpm/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 Latm/min ≡ 1 atm 1 L/min = 1.688 75 W
litre-atmosphere per second Latm/s ≡ 1 atm 1 L/s = 101.325 W
lusec lusec ≡ 1 LmHg/s [14] ≈ 1.33310−4 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   ≡ 1 t ice melted / 24 h 3 504 W
ton of refrigeration (Imperial)   ≡ 1 BTUIT 1 lng tn/lb 10 min/s 3.938 875103 W
ton of refrigeration (IT)   ≡ 1 BTUIT 1 sh tn/lb 10 min/s 3.516 853103 W
watt (SI unit) W The power which in one second of time gives rise to one joule of energy.[24] = 1 W = 1 J/s = 1 Nm/s = 1 kgm2/s3

Action

Action
Name of unit Symbol Definition Relation to SI units
atomic unit of action au /2π 1.054 571 6810−34 Js[27]

Dynamic viscosity

Dynamic viscosity
Name of unit Symbol Definition Relation to SI units
pascal second (SI unit) Pas ≡ Ns/m2 , kg/(ms) = 1 Pas
poise (cgs unit) P ≡ 10−1 Pas = 0.1 Pas
pound per foot hour lb/(fth) ≡ 1 lb/(fth) 4.133 78910−4 Pas
pound per foot second lb/(fts) ≡ 1 lb/(fts) 1.488164 Pas
pound-force second per square foot lbfs/ft2 ≡ 1 lbfs/ft2 47.88026 Pas
pound-force second per square inch lbfs/in2 ≡ 1 lbfs/in2 6,894.757 Pas

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.[8] = 1 A
electromagnetic unit; abampere (cgs unit) abamp ≡ 10 A = 10 A
esu per second; statampere (cgs unit) esu/s ≡ (0.1 Am/s) / c 3.33564110−10
 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 46210−19 C
coulomb (SI unit) C ≡ The amount of electricity carried in one second of time by one ampere of current.[24] = 1 C = 1 As
faraday F ≡ 1 mol NAe 96 485.3383 C
statcoulomb; franklin; electrostatic unit (cgs unit) statC; Fr; esu ≡ (0.1 Am) / c 3.335 64110−10 C

Electric dipole

Electric dipole
Name of unit Symbol Definition Relation to SI units
atomic unit of electric dipole moment ea0   8.478 352 8110−30 Cm[28]
coulomb meter Cm   = 1 C 1 m
debye D = 10−10 esu = 3.3356409510−30 Cm [29]

Electromotive force, electric potential difference

Voltage, electromotive force
Name of unit Symbol Definition Relation to SI units
abvolt (cgs unit) abV ≡ 110−8 V = 110−8 V
statvolt (cgs unit) statV c (1 μJ/Am) = 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.[24] = 1 V = 1 W/A = 1 kgm2/(As3)

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.[24] = 1 Ω = 1 V/A = 1 kgm2/(A2s3)

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.[24] = 1 F = 1 C/V = 1 A2s4/(kgm2)

Magnetic flux

magnetic flux
Name of unit Symbol Definition Relation to SI units
maxwell (CGS unit) Mx ≡ 10−8 Wb[30] = 110−8 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.[24] = 1 Wb = 1 Vs = 1 kgm2/(As2)

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 = 110−4 T [31]
tesla (SI unit) T Wb/m2 = 1 T = 1 Wb/m2 = 1 kg/(As2)

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.[24] = 1 H = 1 Wb/A = 1 kgm2/(As)2

Temperature

Temperature
Name of unit Symbol Definition Conversion to kelvin
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 Raumur R [K] = [R] 5/4 + 273.15
degree Rmer R [K] = ([R] − 7.5) 40/21 + 273.15
kelvin (SI base unit) K ≡ 1/273.16 of the thermodynamic temperature of the triple point of water.[8] ≡ 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 = 8103 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 5401012 hertz and that has a radiant intensity in that direction of 1/683 watt per steradian.[8] = 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.[32] Approximately 0.981 cd.[14] ≈ 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[14]) 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 ≈ 1104 cd/m2

Luminous flux

Luminous flux
Name of unit Symbol Definition Relation to SI units
lumen (SI unit) lm ≡ cdsr = 1 lm = 1 cdsr

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 = 1104 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 ≡ 3.71010 Bq = 3.71010 Bq [33]
rutherford (H) rd ≡ 1 MBq = 1106 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.[34]

Radiation - exposure

Radiation - exposure
Name of unit Symbol Definition Relation to SI units
roentgen R 1 R ≡ 2.5810−4 C/kg[30] = 2.5810−4 C/kg

The roentgen is not a SI unit and the NIST strongly discourages its continued use.[35]

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 [36] = 1 Gy
rad rad ≡ 0.01 Gy[30] = 0.01 Gy

Radiation - equivalent dose

Radiation - equivalent dose
Name of unit Symbol Definition Relation to SI units
Rntgen equivalent man rem ≡ 0.01 Sv = 0.01 Sv
sievert (SI unit) Sv ≡ 1 J/kg[34] = 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.[37]

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

See also

References

  1. ^ United States Naval Observatory. (2009). Selected Astronomical Constants, 2009. Accessed May 10, 2009
  2. ^ "NIST Reference on Constants, Units, and Uncertainty."(2006). National Institute of Standards and Technology. Retrieved February 22, 2008.
  3. ^ a b National Institute of Standards and Technology General Tables of Units of Measurement
  4. ^ a b c d e f g h i j k l m n Lide, D. (Ed.). (1990). Handbook of Chemistry and Physics (71st ed). Boca Raton, FL: CRC Press. Section 1.
  5. ^ a b 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.
  6. ^ The International Astronomical Union and Astronomical Units
  7. ^ Klein, Herbert Arthur. (1988). The Science of Measurement: a Historical Survey. Mineola, NY: Dover Publications 0-4862-5839-4.
  8. ^ a b c d e f The International System of Units, Section 2.1 (8 ed.), Bureau International des Poids et Mesures, 2006, http://www.bipm.org/en/si/si_brochure/chapter2/2-1/, retrieved August 26, 2009 
  9. ^ International System of Units, 8th ed. (2006), Bureau International des Poids et Mesures, Section 4.1 Table 8.
  10. ^ P. Kenneth Seidelmann, Ed. (1992). Explanatory Supplement to the Astronomical Almanac. Sausalito, CA: University Science Books. p. 716 and s.v. parsec in Glossary.
  11. ^ a b c Whitelaw, Ian. (2007). A Measure of All Things: The Story of Man and Measurement. New York: Macmillan 0-312-37026-1. p. 152.
  12. ^ a b 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 2nd ed. New York: The Century Co. p. 142150.
  13. ^ Pasko, Wesley Washington (1894). American dictionary of printing and bookmaking. (1894). New York: Howard Lockwood. p. 521.
  14. ^ a b c d e f Rowlett, Russ (2005), How Many? A Dictionary of Units of Measurement, http://www.unc.edu/~rowlett/units/index.html 
  15. ^ Thompson, A. and Taylor, B.N. (2008). Guide for the Use of the International System of Units (SI). National Institute of Standards and Technology Special Publication 811. p. 57.
  16. ^ a b c d e U.S. Code of Federal Regulations, Title 21, Section 101.9, Paragraph (b)(5)(viii), http://ecfr.gpoaccess.gov/cgi/t/text/text-idx?c=ecfr&rgn=div8&view=text&node=21:2.0.1.1.2.1.1.6&idno=21, retrieved August 29, 2009 
  17. ^ Barry N. Taylor, Ed.,NIST Special Publication 330: The International System of Units (SI) (2001 Edition), Washington: U.S. Government Printing Office, 43,"The 12th Conference Generale des Poids et Mesures (CGPM)declares that the word litre may be employed as a special name for the cubic decimetre".
  18. ^ CODATA Value: atomic uint 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 [1] and quintal on the English translation of that page [2]; the unit is marked "spcifiquement suisse !"
  20. ^ a b Pedersen O. (1983). "Glossary" in Coyne, G., Hoskin, M., and Pedersen, O. Gregorian Reform of the Calendar: Proceedings of the Vatican Conference to Commemorate its 400th Anniversary. Vatican Observatory. Available from Astrophysics Data System.
  21. ^ Richards, E.G. (1998), Mapping Time, Oxford University Press, pp. 9495, ISBN 0-19-850413-6 
  22. ^ Steel, Duncan (2000), Marking Time, John Wiley & Sons, p. 46, ISBN 0-471-29827-1 
  23. ^ CODATA Value: atomic unit of force. (2006). National Institute of Standards and Technology. Retrieved September 14, 2008.
  24. ^ a b c d e f g h i Comit International des Poids et Mesures, Resolution 2, 1946, http://www.bipm.org/en/CIPM/db/1946/2/, retrieved August 26, 2009 
  25. ^ a b c d e f g h i j k l m n o p Barry N. Taylor, (April 1 995), Guide for the Use of the International System of Units (SI) (NIST Special Publication 811), Washington, DC: U.S. Government Printing Office, pp. 5768.
  26. ^ Barry N. Taylor, (April 1995), Guide for the Use of the International System of Units (SI) (NIST Special Publication 811), Washington, DC: U.S. Government Printing Office, p. 5.
  27. ^ International System of Units, 8th ed. (2006), Bureau International des Poids et Mesures, Section 4.1 Table 7.
  28. ^ The NIST Reference on Constants, Units, and Uncertainty, 2006, http://physics.nist.gov/cgi-bin/cuu/Value?auedm, retrieved August 26, 2009 
  29. ^ Robert G. Mortimer Physical chemistry,Academic Press, 2000 ISBN 0125083459, page 677
  30. ^ a b c NIST Guide to SI Units, Appendix B.9, http://physics.nist.gov/Pubs/SP811/appenB9.html, retrieved August 27, 2009 
  31. ^ Standard for the Use of the International System of Units (SI): The Modern Metric System IEEE/ASTM SI 10-1997. (1997). New York and West Conshohocken, PA: Institute of Electrical and Electronics Engineers and American Society for Testing and Materials. Tables A.1 through A.5.
  32. ^ The NIST Reference on Constants, Units, and Uncertainty, http://physics.nist.gov/cuu/Units/candela.html, retrieved August 28, 2009 
  33. ^ Ambler Thompson & Barry N. Taylor. (2008). Guide for the Use of the International System of Units (SI). Special Publication 811. Gaithersburg, MD: National Institute of Standards and Technology. p. 10.
  34. ^ a b The International System of Units, Section 2.2.2., Table 3 (8 ed.), Bureau International des Poids et Mesures, 2006, http://www.bipm.org/en/si/si_brochure/chapter2/2-2/table3.html, retrieved August 27, 2009 
  35. ^ The NIST Guide to the SI (Special Publication 811), section 5.2, 2008, http://physics.nist.gov/Pubs/SP811/sec05.html#5.2, retrieved August 27, 2009 
  36. ^ Ambler Thompson & Barry N. Taylor. (2008). Guide for the Use of the International System of Units (SI). Special Publication 811. Gaithersburg, MD: National Institute of Standards and Technology. p. 5.
  37. ^ Comit international des poids et mesures, 2002, Recommendation 2, http://www.bipm.org/en/CIPM/db/2002/2/, retrieved August 27, 2009 

External links