List of conversion factors
This section needs additional citations for verification. (January 2011) |
This article gives a list of
The following quantities are considered:
.Symbol | Definition |
---|---|
≡ | exactly equal |
≈ | approximately equal to |
≘ | (exactly) corresponds to (different types of quantity describing the same phenomenon) |
digits | indicates that digits repeat infinitely (e.g. 8.294369 corresponds to 8.294369369369369...) |
(H) | of chiefly historical interest |
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 [1] |
attometre |
am | ≡ 1×10−18 m | ≡ 1×10−18 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(17)×10−11 m[2] |
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 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 | ftm | ≡ 6 ft [4] | = 1.8288 m |
femtometre | fm | ≡ 1×10−15 m | ≡ 1×10−15 m |
fermi |
fm | ≡ 1×10−15 m[4] | ≡ 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, metric |
mf | ≡ 300 mm | ≡ 0.3 m |
foot, metric (Mesures usuelles) (H) | ≡ 1⁄3 m | ≡ 0.3 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 [5] | ≈ 0.304800610 m |
french; charriere | F | ≡ 1⁄3 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 | ≡ 2.54 cm ≡ 1⁄36 yd ≡ 1⁄12 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 | ≈ 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 [6] | ≡ 9.4607304725808×1015 m |
line | ln | ≡ 1⁄12 in [7] | = 0.002116 m |
link (Gunter's; Surveyor's) | lnk | ≡ 1⁄100 ch [4] ≡ 0.66 ft (US) ≡ 7.92 in | ≈ 0.2011684 m |
link (Ramsden's; Engineer's) | lnk | ≡ 1 ft [4] | = 0.3048 m |
metre (SI base unit) (meter) |
m | ≡ Distance light travels in 1⁄299792458 of a second in vacuum.[8] | (SI base unit) |
mickey | ≡ 1⁄200 in | = 1.27×10−4 m | |
micrometre (old: micron) | μ; μm | ≡ 1×10−6 m | ≡ 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 [4] | = 0.05715 m | |
nanometre | nm | ≡ 1×10−9 m | ≡ 1×10−9 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 | Distant point with a parallax shift of one arc second from a base of one astronomical unit. ≡ 648000/π |
≈ 30856775814913700 m[12] |
pica | ≡ 12 points | Dependent on point measures. | |
picometre | pm | ≡ 1×10−12 m | ≡ 1×10−12 m |
point (American, English)[13][14] | pt | ≡ 1⁄72.272 in | ≈ 0.000351450 m |
point (Didot; European) [14][15] | pt | ≡ 1⁄12 × 1⁄72 of pied du roi; After 1878: ≡ 5⁄133 cm |
≈ 0.00037597 m; After 1878: ≈ 0.00037593985 m |
point (PostScript) [13] | pt | ≡ 1⁄72 in | = 0.0003527 m |
point (TeX) [13] | 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 [4] | = 6.096 m |
shaku (Japan) | ≡ 10/33 m | ≈ 0.303 0303 m | |
span (H) | ≡ 9 in [4] | = 0.2286 m | |
spat[16] | ≡ 1×1012 m | ||
stick (H) | ≡ 2 in | = 0.0508 m | |
toise (French, post 1667) (H) | T | ≡ 27000/13853 m | ≈ 1.949 0363 m |
twip | twp | ≡ 1⁄1440 in | = 1.7638×10−5 m |
x unit; siegbahn | xu | ≈ 1.0021×10−13 m [4] | |
yard (International) | yd | ≡ 0.9144 m [5] ≡ 3 ft ≡ 36 in | ≡ 0.9144 m |
yoctometre |
ym | ≡ 1×10−24 m | ≡ 1×10−24 m |
zeptometre |
zm | ≡ 1×10−21 m | ≡ 1×10−21 m |
Area
Name of unit | Symbol | Definition | Relation to SI units |
---|---|---|---|
acre (international) | ac | ≡ 1 ch × 10 ch = 4840 sq yd | ≡ 4046.8564224 m2 |
acre (US survey) | ac | ≡ 10 sq ch = 4840 sq yd, also 43560 sq ft | ≈ 4046.873 m2[17] |
are | a | ≡ 100 m2 | ≡ 100 m2 |
barn | b | ≡ 10−28 m2 | ≡ 10−28 m2 |
barony | ≡ 4000 ac | ≡ 1.61874256896×107 m2 | |
board | bd | ≡ 1 in × 1 ft | ≡ 7.74192×10−3 m2 |
boiler horsepower equivalent direct radiation | bhp EDR | ≡ 1 ft2 × 1 bhp / (240 BTUIT/h) | ≈ 12.958174 m2 |
circular inch | circ in | ≡ π⁄4 sq in | ≈ 5.067075×10−4 m2 |
circular mil; circular thou | circ mil | ≡ π⁄4 mil2 | ≈ 5.067075×10−10 m2 |
cord | ≡ 192 bd | ≡ 1.48644864 m2 | |
cuerda (PR Survey) | cda | ≡ 1 cda x 1 cda = 0.971222 acre | ≡ 3930.395625 m2 |
dunam | ≡ 1000 m2 | ≡ 1000 m2 | |
guntha (India) |
≡ 121 sq yd | ≈ 101.17 m2 | |
hectare | ha | ≡ 10000 m2 | ≡ 10000 m2 |
hide | ≈ 120 ac (variable) | ≈ 5×105 m2 | |
rood | ro | ≡ 1⁄4 ac | = 1011.7141056 m2 |
ping | ≡ 20⁄11 m × 20⁄11 m | ≈ 3.306 m2 | |
section | ≡ 1 mi × 1 mi | = 2.589988110336×106 m2 | |
shed |
≡ 10−52 m2 | = 10−52 m2 | |
square (roofing) | ≡ 10 ft × 10 ft | = 9.290304 m2 | |
square chain (international) | sq ch | ≡ 66 ft × 66 ft = 1⁄10 ac | ≡ 404.68564224 m2 |
square chain (US Survey) | sq ch | ≡ 66 ft (US) × 66 ft (US) = 1⁄10 US survey acre | ≈ 404.6873 m2 |
square foot | sq ft | ≡ 1 ft × 1 ft | ≡ 9.290304×10−2 m2 |
square foot (US Survey) | sq ft | ≡ 1 ft (US) × 1 ft (US) | ≈ 9.2903411613275×10−2 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 | = 4.0468564224×10−2 m2 |
square link (Gunter's)(US Survey) | sq lnk | ≡ 1 lnk × 1 lnk ≡ 0.66 ft (US) × 0.66 ft (US) | ≈ 4.046872×10−2 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 | ≡ 2.589988110336×106 m2 |
square mile (US Survey) | sq mi | ≡ 1 mi (US) × 1 mi (US) | ≈ 2.58999847×106 m2 |
square rod/pole/perch | sq rd | ≡ 1 rd × 1 rd | = 25.29285264 m2 |
square yard (International) | sq yd | ≡ 1 yd × 1 yd | ≡ 0.83612736 m2 |
stremma | ≡ 1000 m2 | = 1000 m2 | |
township | ≡ 36 sq mi (US) | ≈ 9.323994×107 m2 | |
yardland | ≈ 30 ac | ≈ 1.2×105 m2 |
Volume
Name of unit | Symbol | Definition | Relation to SI units |
---|---|---|---|
acre-foot | ac ft | ≡ 1 ac x 1 ft = 43560 cu ft | = 1233.48183754752 m3 |
acre-inch | ≡ 1 ac × 1 in | = 102.79015312896 m3 | |
barrel (imperial) | bl (imp) | ≡ 36 gal (imp) | = 0.16365924 m3 |
barrel (petroleum); archaic blue-barrel | bl; bbl | ≡ 42 gal (US) | ≡ 0.158987294928 m3 |
barrel (US dry) | bl (US) | ≡ 105 qt (US) = 105/32 bu (US lvl) | = 0.115628198985075 m3 |
barrel (US fluid) | fl bl (US) | ≡ 31+1⁄2 gal (US) | = 0.119240471196 m3 |
board-foot |
bdft | ≡ 144 cu in | ≡ 2.359737216×10−3 m3 |
bucket (imperial) | bkt | ≡ 4 gal (imp) | = 0.01818436 m3 |
bushel (imperial) | bu (imp) | ≡ 8 gal (imp) | = 0.03636872 m3 |
bushel (US dry heaped) | bu (US) | ≡ 1+1⁄4 bu (US lvl) | = 0.0440488377086 m3 |
bushel (US dry level) | bu (US lvl) | ≡ 2150.42 cu in | = 0.03523907016688 m3 |
butt, pipe | ≡ 126 gal (US) (wine) | = 0.476961884784 m3 | |
coomb | ≡ 4 bu (imp) | = 0.14547488 m3 | |
cord ( firewood ) |
≡ 8 ft × 4 ft × 4 ft | = 3.624556363776 m3 | |
cord-foot | ≡ 16 cu ft | = 0.453069545472 m3 | |
cubic fathom | cu fm | ≡ 1 fm × 1 fm × 1 fm | = 6.116438863872 m3 |
cubic foot | ft3 | ≡ 1 ft × 1 ft × 1 ft | ≡ 0.028316846592 m3 |
cubic inch | in3 | ≡ 1 in × 1 in × 1 in | ≡ 16.387064×10−6 m3 |
cubic metre (SI unit) | m3 | ≡ 1 m × 1 m × 1 m | ≡ 1 m3 |
cubic mile | cu mi | ≡ 1 mi × 1 mi × 1 mi | ≡ 4168181825.440579584 m3 |
cubic yard | yd3 | ≡ 27 cu ft | ≡ 0.764554857984 m3 |
cup (breakfast) | ≡ 10 fl oz (imp) | = 284.130625×10−6 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) | = 236.5882365×10−6 m3 |
cup (US food nutrition labeling) | c (US) | ≡ 240 mL[18] | = 2.4×10−4 m3 |
dash (imperial) | ≡ 1⁄192 gi (imp) = 1/8 tsp (imp) | = 739.92350260416×10−9 m3 | |
dash (US) | ≡ 1⁄48 US fl oz = 1/8 US tsp | = 616.11519921875×10−9 m3 | |
dessertspoon (imperial) |
≡ 1⁄12 gi (imp) | = 11.8387760416×10−6 m3 | |
drop (imperial) | gtt | ≡ 1⁄288 fl oz (imp) | = 98.6564670138×10−9 m3 |
drop (imperial) (alt) | gtt | ≡ 1⁄1824 gi (imp) | ≈ 77.886684×10−9 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 | = 82.14869322916×10−9 m3 |
drop (US) (alt) | gtt | ≡ 1⁄456 US fl oz | ≈ 64.85423149671×10−9 m3 |
drop (US) (alt) | gtt | ≡ 1⁄576 US fl oz | ≈ 51.34293326823×10−9 m3 |
fifth | ≡ 1⁄5 US gal | = 757.0823568×10−6 m3 | |
firkin | ≡ 9 gal (imp) | = 0.04091481 m3 | |
fluid drachm (imperial) | fl dr | ≡ 1⁄8 fl oz (imp) | = 3.5516328125×10−6 m3 |
fluid dram (US); US fluidram | fl dr | ≡ 1⁄8 US fl oz | = 3.6966911953125×10−6 m3 |
fluid scruple (imperial) |
fl s | ≡ 1⁄24 fl oz (imp) | = 1.18387760416×10−6 m3 |
gallon (beer) | beer gal | ≡ 282 cu in | = 4.621152048×10−3 m3 |
gallon (imperial) | gal (imp) | ≡ 4.54609 L | ≡ 4.54609×10−3 m3 |
gallon (US dry) | gal (US) | ≡ 1⁄8 bu (US lvl) | = 4.40488377086×10−3 m3 |
gallon (US fluid; Wine) | gal (US) | ≡ 231 cu in | ≡ 3.785411784×10−3 m3 |
gill (imperial); Noggin | gi (imp); nog | ≡ 5 fl oz (imp) | = 142.0653125×10−6 m3 |
gill (US) | gi (US) | ≡ 4 US fl oz | = 118.29411825×10−6 m3 |
hogshead (imperial) | hhd (imp) | ≡ 2 bl (imp) | = 0.32731848 m3 |
hogshead (US) | hhd (US) | ≡ 2 fl bl (US) | = 0.238480942392 m3 |
jigger (bartending) |
≡ 1+1⁄2 US fl oz | ≈ 44.36×10−6 m3 | |
kilderkin |
≡ 18 gal (imp) | = 0.08182962 m3 | |
lambda | λ | ≡ 1 mm3 | = 1×10−9 m3 |
last | ≡ 80 bu (imp) | = 2.9094976 m3 | |
litre (liter) |
L or l | ≡ 1 dm3 [19] | ≡ 0.001 m3 |
load | ≡ 50 cu ft | = 1.4158423296 m3 | |
minim (imperial) | min | ≡ 1⁄480 fl oz (imp) = 1/60 fl dr (imp) | = 59.1938802083×10−9 m3 |
minim (US) | min | ≡ 1⁄480 US fl oz = 1⁄60 US fl dr | = 61.611519921875×10−9 m3 |
ounce (fluid imperial) | fl oz (imp) | ≡ 1⁄160 gal (imp) | ≡ 28.4130625×10−6 m3 |
ounce (fluid US customary) | US fl oz | ≡ 1⁄128 gal (US) | ≡ 29.5735295625×10−6 m3 |
ounce (fluid US food nutrition labeling) | US fl oz | ≡ 30 mL[18] | ≡ 3×10−5 m3 |
peck (imperial) | pk | ≡ 2 gal (imp) | = 9.09218×10−3 m3 |
peck (US dry) | pk | ≡ 1⁄4 US lvl bu | = 8.80976754172×10−3 m3 |
perch |
per | ≡ 16+1⁄2 ft × 1+1⁄2 ft × 1 ft | = 0.700841953152 m3 |
pinch (imperial) | ≡ 1⁄384 gi (imp) = 1⁄2 dash (imp) | = 369.961751302083×10−9 m3 | |
pinch (US) | ≡ 1⁄96 US fl oz = 1⁄2 US dash | = 308.057599609375×10−9 m3 | |
pint (imperial) | pt (imp) | ≡ 1⁄8 gal (imp) | = 568.26125×10−6 m3 |
pint (US dry) | pt (US dry) | ≡ 1⁄64 bu (US lvl) ≡ 1⁄8 gal (US dry) | = 550.6104713575×10−6 m3 |
pint (US fluid) | pt (US fl) | ≡ 1⁄8 gal (US) | = 473.176473×10−6 m3 |
pony | ≡ 3⁄4 US fl oz | = 22.180147171875×10−6 m3 | |
pottle; quartern | ≡ 1⁄2 gal (imp) = 80 fl oz (imp) | = 2.273045×10−3 m3 | |
quart (imperial) | qt (imp) | ≡ 1⁄4 gal (imp) | = 1.1365225×10−3 m3 |
quart (US dry) | qt (US) | ≡ 1⁄32 bu (US lvl) = 1⁄4 gal (US dry) | = 1.101220942715×10−3 m3 |
quart (US fluid) | qt (US) | ≡ 1⁄4 gal (US fl) | = 946.352946×10−6 m3 |
quarter; pail | ≡ 8 bu (imp) | = 0.29094976 m3 | |
register ton | ≡ 100 cu ft | = 2.8316846592 m3 | |
sack (US) | ≡ 3 bu (US lvl) | = 0.10571721050064 m3 | |
seam | ≡ 8 bu [16] | = 0.29095 m3 | |
shot (US) | usually 1.5 US fl oz[16] | ≈ 44.4×10−6 m3 | |
strike (imperial) | ≡ 2 bu (imp) | = 0.07273744 m3 | |
strike (US) | ≡ 2 bu (US lvl) | = 0.07047814033376 m3 | |
tablespoon (Australian metric) | ≡ 20.0×10−6 m3 | ||
tablespoon (Canadian) | tbsp | ≡ 1⁄2 fl oz (imp) | = 14.20653125×10−6 m3 |
tablespoon (imperial) | tbsp | ≡ 5⁄8 fl oz (imp) | = 17.7581640625×10−6 m3 |
tablespoon (metric) | ≡ 15×10−6 m3 | ||
tablespoon (US customary) | tbsp | ≡ 1⁄2 US fl oz | = 14.78676478125×10−6 m3 |
tablespoon (US food nutrition labeling) | tbsp | ≡ 15 mL[18] | = 15×10−6 m3 |
teaspoon (Canadian) | tsp | ≡ 1⁄6 fl oz (imp) | = 4.735510416×10−6 m3 |
teaspoon (imperial) | tsp | ≡ 1⁄24 gi (imp) | = 5.91938802083×10−6 m3 |
teaspoon (metric) | ≡ 5.0×10−6 m3 | ≡ 5.0×10−6 m3 | |
teaspoon (US customary) | tsp | ≡ 1⁄6 US fl oz | = 4.92892159375×10−6 m3 |
teaspoon (US food nutrition labeling) | tsp | ≡ 5 mL[18] | = 5×10−6 m3 |
timber foot |
≡ 1 cu ft | = 0.028316846592 m3 | |
ton (displacement) | ≡ 35 cu ft | = 0.99108963072 m3 | |
ton (freight) | ≡ 40 cu ft | = 1.13267386368 m3 | |
ton (water) | ≡ 28 bu (imp) | = 1.01832416 m3 | |
tun | ≡ 252 gal (wine) | = 0.953923769568 m3 | |
wey (US) | ≡ 40 bu (US lvl) | = 1.4095628066752 m3 |
Plane angle
Name of unit | Symbol | Definition | Relation to SI units |
---|---|---|---|
NATO mil | (various) | ≡ 2π⁄6400 rad | ≈ 0.981748×10−3 rad |
Swedish streck | ≡ 2π⁄6300 rad | ≈ 0.997302×10−3 rad | |
milliradian | mrad | ≡ 1⁄1000 rad | ≈ 1×10−3 rad |
Warsaw Pact mil | ≡ 2π⁄6000 rad | ≈ 1.047167×10−3 rad | |
arcminute ; MOA |
' | ≡ 1°⁄60 | ≈ 0.290888×10−3 rad |
arcsecond |
" | ≡ 1°⁄3600 | ≈ 4.848137×10−6 rad |
centesimal minute of arc |
' | ≡ 1⁄100 grad | ≈ 0.157080×10−3 rad |
centesimal second of arc |
" | ≡ 1⁄10000 grad | ≈ 1.570796×10−6 rad |
degree (of arc) | ° | ≡ 1⁄360 of a revolution ≡ π⁄180 rad | ≈ 17.453293×10−3 rad |
grad ; gradian; gon |
grad | ≡ 1⁄400 of a revolution ≡ π⁄200 rad ≡ 0.9° | ≈ 15.707963×10−3 rad |
octant |
≡ 45° | ≈ 0.785398 rad | |
quadrant | ≡ 90° | ≈ 1.570796 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° | ≈ 1.047198 rad | |
sign | ≡ 30° | ≈ 0.523599 rad |
Solid angle
Name of unit | Symbol | Definition | Relation to SI units |
---|---|---|---|
spat | ≡ 4π sr[16] – The solid angle subtended by a sphere at its centre. | ≈ 12.56637 sr | |
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 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.
- The symbol g0 is used to denote standard gravity in order to avoid confusion with the (upright) g symbol for gram.
Name of unit | Symbol | Definition | Relation to SI units |
---|---|---|---|
atomic mass unit, unified |
u; AMU | Same as dalton (see below) | ≈ 1.660539040(20)×10−27 kg[3] |
atomic unit of mass, electron rest mass | me | ≈ 9.10938291(40)×10−31 kg[20] | |
bag (coffee) | ≡ 60 kg | = 60 kg | |
bag (Portland cement) | ≡ 94 lb av | = 42.63768278 kg | |
barge | ≡ 22+1⁄2 short ton | = 20411.65665 kg | |
carat |
kt | ≡ 3+1⁄6 gr | = 205.1965483 mg |
carat (metric) |
ct | ≡ 200 mg | = 200 mg |
clove |
≡ 8 lb av | = 3.62873896 kg | |
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 | ≈ 1.660538921(73)×10−27 kg[3] |
dram (apothecary; troy) | dr t | ≡ 60 gr | = 3.8879346 g |
dram (avoirdupois) | dr av | ≡ 27+11⁄32 gr | = 1.7718451953125 g |
electronvolt mass-equivalent | eV/c2 | ≡ 1 eV / c2 | = 1.78266184(45)×10−36 kg[3] |
gamma | γ | ≡ 1 μg | = 1 μg |
grain |
gr | ≡ 1⁄7000 lb av | ≡ 64.79891 mg |
grave | gv | grave was the original name of the kilogram | ≡ 1 kg |
hundredweight (long) | long cwt or cwt | ≡ 112 lb av | = 50.80234544 kg |
hundredweight (short); cental | sh cwt | ≡ 100 lb av | = 45.359237 kg |
hyl ; metric slug |
≡ 1 kgf / 1 m/s2 | = 9.80665 kg | |
kilogram (kilogramme) |
kg | ≈ mass of the prototype near Paris ≈ mass of 1 litre of water |
(SI base unit)[8] |
kip | kip | ≡ 1000 lb av | = 453.59237 kg |
mark | ≡ 8 oz t | = 248.8278144 g | |
mite | ≡ 1⁄20 gr | = 3.2399455 mg | |
mite (metric) | ≡ 1⁄20 g | = 50 mg | |
ounce (apothecary; troy) |
oz t | ≡ 1⁄12 lb t | = 31.1034768 g |
ounce (avoirdupois) | oz av | ≡ 1⁄16 lb | = 28.349523125 g |
ounce (US food nutrition labelling) | oz | ≡ 28 g[18] | = 28 g |
pennyweight | dwt; pwt | ≡ 1⁄20 oz t | = 1.55517384 g |
point |
≡ 1⁄100 ct | = 2 mg | |
pound (avoirdupois) | lb av | ≡ 0.45359237 kg = 7000 grains | ≡ 0.45359237 kg |
pound (metric) | ≡ 500 g | = 500 g | |
pound (troy) | lb t | ≡ 5760 grains | = 0.3732417216 kg |
quarter (imperial) | ≡ 1⁄4 long cwt = 2 st = 28 lb av | = 12.70058636 kg | |
quarter (informal) | ≡ 1⁄4 short ton | = 226.796185 kg | |
quarter, long (informal) | ≡ 1⁄4 long ton | = 254.0117272 kg | |
quintal (metric) |
q | ≡ 100 kg | = 100 kg |
scruple (apothecary) | s ap | ≡ 20 gr | = 1.2959782 g |
sheet | ≡ 1⁄700 lb av | = 647.9891 mg | |
slug; geepound | slug | ≡ g0 × 1 lb av × 1 s2/ft | ≈ 14.593903 kg |
stone |
st | ≡ 14 lb av | = 6.35029318 kg |
ton, assay (long) |
AT | ≡ 1 mg × 1 long ton ÷ 1 oz t | = 32.6 g |
ton, assay (short) |
AT | ≡ 1 mg × 1 short ton ÷ 1 oz t | = 29.16 g |
ton, long | long tn or ton | ≡ 2240 lb | = 1016.0469088 kg |
ton, short | sh tn | ≡ 2000 lb | = 907.18474 kg |
mts unit) |
t | ≡ 1000 kg | = 1000 kg |
wey | ≡ 252 lb = 18 st | = 114.30527724 kg (variants exist) | |
zentner | Ztr. | Definitions vary.[16][21] |
Density
Name of unit | Symbol | Definition | Relation to SI units |
---|---|---|---|
gram per millilitre | g/mL | ≡ g/mL | = 1000 kg/m3 |
kilogram per cubic metre (SI unit) | kg/m3 | ≡ kg/m3 | = 1 kg/m3 |
kilogram per litre | kg/L | ≡ kg/L | = 1000 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
Name of unit | Symbol | Definition | Relation to SI units |
---|---|---|---|
atomic unit of time | a.u. | ≡ a0/(α⋅c) | ≈ 2.418884254×10−17 s |
Callippic cycle | ≡ 441 mo (hollow) + 499 mo (full) = 76 a of 365.25 d | = 2.396736 Gs or 2.3983776 Gs[note 1] | |
century | c | ≡ 100 years (100 a) | = 3.1556952 Gs[note 2][note 3] |
day | d | = 24 h = 1440 min | = 86.4 ks[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 )
|
≈ 86.1641 ks |
decade | dec | ≡ 10 years (10 a) | = 315.569520 Ms[note 2][note 3] |
fortnight | fn | ≡ 2 wk | = 1.2096 Ms[note 3] |
helek | ≡ 1⁄1080 h | = 3.3 s | |
Hipparchic cycle | ≡ 4 Callippic cycles - 1 d | = 9.593424 Gs | |
hour | h | ≡ 60 min | = 3.6 ks[note 3] |
jiffy | j | ≡ 1⁄60 s | = 16.6 ms |
jiffy (alternative) | ja | ≡ 1⁄100 s | = 10 ms |
kè (quarter of an hour) | ≡ 1⁄4 h = 1⁄96 d = 15 min | = 900 s | |
kè (traditional) | ≡ 1⁄100 d = 14.4 min | = 864 s | |
lustre; lūstrum | ≡ 5 a of 365 d[note 4] | = 157.68 Ms | |
Metonic cycle; enneadecaeteris | ≡ 110 mo (hollow) + 125 mo (full) = 6940 d ≈ 19 a | = 599.616 Ms | |
millennium | ≡ 1000 years (1000 a) | = 31.556952 Gs[note 2][note 3] | |
milliday | md | ≡ 1⁄1000 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] | = 2.592×106 s[note 3] |
month (Greg. av.) | mo | = 30.436875 d | ≈ 2.6297 Ms[note 3] |
month (hollow) | mo | ≡ 29 d[22] | = 2.5056 Ms[note 3] |
Month ( synodic ) |
mo | Cycle time of moon phases ≈ 29.530589 d (average) | ≈ 2.551 Ms |
octaeteris | = 48 mo (full) + 48 mo (hollow) + 3 mo (full)[23][24] = 8 a of 365.25 d = 2922 d | = 252.4608 Ms[note 3] | |
Planck time |
≡ ( ℏ⁄c 5)1⁄2
|
≈ 5.39116×10−44 s[25] | |
second (SI base unit) | s | ≡ Time of 9192631770 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 299792458 metres. | (SI base unit) |
shake |
≡ 10−8 s | = 10 ns | |
sigma | ≡ 10−6 s | = 1 μs | |
Sothic cycle | ≡ 1461 a of 365 d | = 46.074096 Gs | |
svedberg | S | ≡ 10−13 s | = 100 fs |
week | wk | ≡ 7 d = 168 h = 10080 min | = 604.8 ks[note 3] |
year (common) | a, y, or yr | 365 d | = 31.536 Ms[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. | = 31.556952 Ms[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 | = 31.5576 Ms |
year (leap) | a, y, or yr | 366 d | = 31.6224 Ms[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 365.24219 d, each day being 86400 SI seconds[27] | ≈ 31.556925 Ms |
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 365.256363 d | ≈ 31.5581497632 Ms |
Notes:
|
Frequency
Name of unit | Symbol | Definition | Relation to SI units |
---|---|---|---|
actions per minute | APM | ≡ 1/60 Hz | ≈ 0.0167 Hz |
cycle per second | cps | ≡ 1 Hz | = 1 cps = 1 Hz |
degree per second | deg/s | ≡ 1 °/s ≡ 1/360 Hz | = 0.0027 Hz |
hertz (SI unit) | Hz | ≡ One cycle per second | = 1 Hz = 1/s |
radian per second | rad/s | ≡ 1/(2π) Hz | ≈ 0.159155 Hz |
revolution per minute |
rpm | ≡ One rpm equals one rotation completed around a fixed axis in one minute of time. | ≈ 0.104719755 rad/s |
Speed or velocity
Name of unit | Symbol | Definition | Relation to SI units |
---|---|---|---|
foot per hour | fph | ≡ 1 ft/h | = 8.46×10−5 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 | ≈ 1.663095×10−4 m/s | |
inch per hour | iph | ≡ 1 in/h | = 7.05×10−6 m/s |
inch per minute | ipm | ≡ 1 in/min | = 4.23×10−4 m/s |
inch per second | ips | ≡ 1 in/s | = 2.54×10−2 m/s |
kilometre per hour |
km/h | ≡ 1 km/h | = 2.7×10−1 m/s |
knot | kn | ≡ 1 nmi/h = 1.852 km/h | = 0.514 m/s |
knot (Admiralty) | kn | ≡ 1 NM (Adm)/h = 1.853184 km/h[28] | = 0.514773 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 | = 0.44704 m/s |
mile per minute | mpm | ≡ 1 mi/min | = 26.8224 m/s |
mile per second | mps | ≡ 1 mi/s | = 1609.344 m/s |
speed of light in vacuum | c | ≡ 299792458 m/s | = 299792458 m/s |
speed of sound in air | s | 1225 to 1062 km/h (761–660 mph or 661–574 kn)[note 1] | ≈ 340 to 295 m/s |
|
A velocity consists of a speed combined with a direction; the speed part of the velocity takes units of speed.
Flow (volume)
Name of unit | Symbol | Definition | Relation to SI units |
---|---|---|---|
cubic foot per minute | CFM[citation needed] | ≡ 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[citation needed] | ≡ 1 gal/d | = 4.381263638×10−8 m3/s |
gallon (US fluid) per hour | GPH[citation needed] | ≡ 1 gal/h | = 1.051503273×10−6 m3/s |
gallon (US fluid) per minute | GPM[citation needed] | ≡ 1 gal/min | = 6.30901964×10−5 m3/s |
litre per minute | l/min or L/min | ≡ 1 L/min | = 1.6×10−5 m3/s |
Acceleration
Name of unit | Symbol | Definition | Relation to SI units |
---|---|---|---|
foot per hour per second | fph/s | ≡ 1 ft/(h⋅s) | = 8.46×10−5 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) | = 4.23×10−4 m/s2 |
inch per second squared | ips2 | ≡ 1 in/s2 | = 2.54×10−2 m/s2 |
knot per second | kn/s | ≡ 1 kn/s | ≈ 5.14×10−1 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 | = 1.609344×103 m/s2 |
standard gravity | g0 | ≡ 9.80665 m/s2 | = 9.80665 m/s2 |
Force
Name of unit | Symbol | Definition | Relation to SI units |
---|---|---|---|
atomic unit of force | ≡ me⋅α2⋅c2⁄a0 | ≈ 8.23872206×10−8 N[30] | |
CGS unit ) |
dyn | ≡ g⋅cm/s2 | = 10−5 N |
kilogram-force; kilopond; grave-force | kgf; kp; gvf | ≡ g0 × 1 kg | = 9.80665 N |
kip; kip-force | kip; kipf; klbf | ≡ g0 × 1000 lb | = 4.4482216152605×103 N |
milligrave-force, gravet-force | mgvf; gvtf | ≡ g0 × 1 g | = 9.80665 mN |
long ton-force | tnf[citation needed] | ≡ g0 × 1 long ton | = 9.96401641818352×103 N |
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 | = 0.27801385095378125 N |
pound-force |
lbf
|
≡ g0 × 1 lb | = 4.4482216152605 N |
poundal | pdl | ≡ 1 lb⋅ft/s2 | = 0.138254954376 N |
short ton-force | tnf[citation needed] | ≡ g0 × 1 short ton | = 8.896443230521×103 N |
sthene ( mts unit) |
sn | ≡ 1 t⋅m/s2 | = 103 N |
Pressure or mechanical stress
Name of unit | Symbol | Definition | Relation to SI units |
---|---|---|---|
atmosphere (standard) |
atm | ≡ 101325 Pa[32] | |
atmosphere (technical) |
at | ≡ 1 kgf/cm2 | = 9.80665×104 Pa[32] |
bar | bar | ≡ 100000 Pa | ≡ 105 Pa |
barye ( CGS unit ) |
≡ 1 dyn/cm2 | = 0.1 Pa | |
centimetre of mercury | cmHg | ≡ 13595.1 kg/m3 × 1 cm × g0 | ≈ 1.33322×103 Pa[32] |
centimetre of water (4 °C) | cmH2O | ≈ 999.972 kg/m3 × 1 cm × g0 | ≈ 98.0638 Pa[32] |
foot of mercury (conventional) | ftHg | ≡ 13595.1 kg/m3 × 1 ft × g0 | ≈ 4.063666×104 Pa[32] |
foot of water (39.2 °F) | ftH2O | ≈ 999.972 kg/m3 × 1 ft × g0 | ≈ 2.98898×103 Pa[32] |
inch of mercury (conventional) | inHg | ≡ 13595.1 kg/m3 × 1 in × g0 | ≈ 3.386389×103 Pa[32] |
inch of water (39.2 °F) | inH2O | ≈ 999.972 kg/m3 × 1 in × g0 | ≈ 249.082 Pa[32] |
kilogram-force per square millimetre | kgf/mm2 | ≡ 1 kgf/mm2 | = 9.80665×106 Pa[32] |
kip per square inch | ksi | ≡ 1 kipf/sq in | ≈ 6.894757×106 Pa[32] |
long ton per square foot | ≡ 1 long ton × g0 / 1 sq ft | ≈ 1.0725178011595×105 Pa | |
micrometre of mercury | μmHg | ≡ 13595.1 kg/m3 × 1 μm × g0 ≈ 0.001 torr | ≈ 0.1333224 Pa[32] |
millimetre of mercury | mmHg
|
≡ 13595.1 kg/m3 × 1 mm × g0 ≈ 1 torr | ≈ 133.3224 Pa[32] |
millimetre of water (3.98 °C) | mmH2O | ≈ 999.972 kg/m3 × 1 mm × g0 = 0.999972 kgf/m2 | = 9.80638 Pa |
pascal (SI unit) | Pa | ≡ N/m2 = kg/(m⋅s2) | = 1 Pa[33] |
pièze ( mts unit) |
pz | ≡ 1000 kg/m⋅s2 | = 103 Pa = 1 kPa |
pound per square foot |
psf | ≡ 1 lbf/ft2 | ≈ 47.88026 Pa[32] |
pound per square inch |
psi | ≡ 1 lbf/in2 | ≈ 6.894757×103 Pa[32] |
poundal per square foot | pdl/sq ft | ≡ 1 pdl/sq ft | ≈ 1.488164 Pa[32] |
short ton per square foot | ≡ 1 short ton × g0 / 1 sq ft | ≈ 9.5760518×104 Pa | |
torr | torr | ≡ 101325⁄760 Pa | ≈ 133.3224 Pa[32] |
Torque or moment of force
Name of unit | Symbol | Definition | Relation to SI units |
---|---|---|---|
pound-force-foot | lbf⋅ft | ≡ g0 × 1 lb × 1 ft | = 1.3558179483314004 N⋅m |
poundal-ft | pdl⋅ft | ≡ 1 lb⋅ft2/s2 | = 4.21401100938048×10−2 N⋅m |
pound force-inch |
lbf⋅in | ≡ g0 × 1 lb × 1 in | = 0.1129848290276167 N⋅m |
kilogram force-meter | kgf⋅m | ≡ g0 × N × m | = 9.80665 N⋅m |
newton-metre (SI unit) | N⋅m | ≡ N × m = kg⋅m2/s2 | = 1 N⋅m |
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 | = 1.05505585262×103 J | |
British thermal unit (mean) | BTUmean | ≈ 1.05587×103 J | |
British thermal unit (thermochemical) | BTUth | ≈ 1.054350×103 J | |
British thermal unit (39 °F) | BTU39 °F | ≈ 1.05967×103 J | |
British thermal unit (59 °F) | BTU59 °F | ≡ 1.054804×103 J | = 1.054804×103 J |
British thermal unit (60 °F) | BTU60 °F | ≈ 1.05468×103 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 at a pressure of 1 atm | ≈ 4.19002 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 | = 1.899100534716×103 J |
cubic centimetre of atmosphere ; standard cubic centimetre |
cc atm; scc | ≡ 1 atm × 1 cm3 | = 0.101325 J |
cubic foot of atmosphere; standard cubic foot | cu ft atm; scf | ≡ 1 atm × 1 ft3 | = 2.8692044809344×103 J |
cubic foot of natural gas | ≡ 1000 BTUIT | = 1.05505585262×106 J | |
cubic yard of atmosphere; standard cubic yard | cu yd atm; scy | ≡ 1 atm × 1 yd3 | = 77.4685209852288×103 J |
electronvolt |
eV | ≡ e × 1 V | ≡ 1.602176634×10−19 J |
CGS unit ) |
erg | ≡ 1 g⋅cm2/s2 | = 10−7 J |
foot-pound force |
ft lbf | ≡ g0 × 1 lb × 1 ft | = 1.3558179483314004 J |
foot-poundal | ft pdl | ≡ 1 lb⋅ft2/s2 | = 4.21401100938048×10−2 J |
gallon-atmosphere (imperial) | imp gal atm | ≡ 1 atm × 1 gal (imp) | = 460.63256925 J |
gallon-atmosphere (US) | US gal atm | ≡ 1 atm × 1 gal (US) | = 383.5568490138 J |
hartree, atomic unit of energy | Eh | ≡ me⋅α2⋅c2 (= 2 Ry) | ≈ 4.359744×10−18 J |
horsepower-hour | hp⋅h | ≡ 1 hp × 1 h | = 2.684519537696172792×106 J |
inch-pound force |
in lbf | ≡ g0 × 1 lb × 1 in | = 0.1129848290276167 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.[31] | = 1 J = 1 m⋅N = 1 kg⋅m2/s2 = 1 C⋅V = 1 W⋅s |
kilocalorie; large calorie | kcal; Cal | ≡ 1000 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 |
atmosphere |
l atm; sl | ≡ 1 atm × 1 L | = 101.325 J |
quad |
≡ 1015 BTUIT | = 1.05505585262×1018 J | |
rydberg | Ry | ≡ R∞⋅ℎ⋅c | ≈ 2.179872×10−18 J |
therm (E.C.) | ≡ 100000 BTUIT | = 105.505585262×106 J | |
therm (US) | ≡ 100000 BTU59 °F | = 105.4804×106 J | |
thermie | th | ≡ 1 McalIT | = 4.1868×106 J |
tonne of coal equivalent |
TCE | ≡ 7 Gcalth | = 29.288×109 J |
tonne of oil equivalent | toe | ≡ 10 GcalIT | = 41.868×109 J |
TNT |
tTNT | ≡ 1 Gcalth | = 4.184×109 J |
watt-hour |
W⋅h | ≡ 1 W × 1 h | = 3.6×103 J |
watt-second |
W⋅s | ≡ 1 J | = 1×100 J |
Power or heat flow rate
Name of unit | Symbol | Definition | Relation to SI units |
---|---|---|---|
atmosphere-cubic centimetre per minute |
atm ccm[citation needed] | ≡ 1 atm × 1 cm3/min | = 1.68875×10−3 W |
atmosphere-cubic centimetre per second | atm ccs[citation needed] | ≡ 1 atm × 1 cm3/s | = 0.101325 W |
atmosphere-cubic foot per hour | atm cfh[citation needed] | ≡ 1 atm × 1 cu ft/h | = 0.79700124704 W |
atmosphere-cubic foot per minute | atm cfm[citation needed] | ≡ 1 atm × 1 cu ft/min | = 47.82007468224 W |
atmosphere-cubic foot per second | atm cfs[citation needed] | ≡ 1 atm × 1 cu ft/s | = 2.8692044809344×103 W |
BTU (International Table) per hour |
BTUIT/h | ≡ 1 BTUIT/h | ≈ 0.293071 W |
BTU (International Table) per minute | BTUIT/min | ≡ 1 BTUIT/min | ≈ 17.584264 W |
BTU (International Table) per second | BTUIT/s | ≡ 1 BTUIT/s | = 1.05505585262×103 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 | ≈ 3.766161×10−4 W |
foot-pound-force per minute | ft⋅lbf/min | ≡ 1 ft lbf/min | = 2.259696580552334×10−2 W |
foot-pound-force per second | ft⋅lbf/s | ≡ 1 ft lbf/s | = 1.3558179483314004 W |
horsepower (boiler) | hp | ≈ 34.5 lb/h × 970.3 BTUIT/lb | ≈ 9809.5 W[34] |
horsepower (European electrical) | hp | ≡ 75 kp⋅m/s | = 736 W[citation needed] |
horsepower (electrical) | hp | ≡ 746 W | = 746 W[34] |
horsepower (mechanical) | hp | ≡ 550 ft⋅lbf/s[34] | = 745.69987158227022 W |
horsepower (metric) | hp or PS | ≡ 75 m⋅kgf/s | = 735.49875 W[34] |
litre-atmosphere per minute | L·atm/min | ≡ 1 atm × 1 L/min | = 1.68875 W |
litre-atmosphere per second | L·atm/s | ≡ 1 atm × 1 L/s | = 101.325 W |
lusec | lusec | ≡ 1 L·µmHg/s [16] | ≈ 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 | ≈ 70.337057 W |
ton of air conditioning | ≡ 2000 lb of ice melted / 24 h | ≈ 3504 W | |
ton of refrigeration (imperial) | ≡ 2240 lb × iceIT / 24 h: iceIT = 144 °F × 2326 J/kg⋅°F | ≈ 3.938875×103 W | |
ton of refrigeration (IT) | ≡ 2000 lb × iceIT / 24 h: iceIT = 144 °F × 2326 J/kg⋅°F | ≈ 3.516853×103 W | |
watt (SI unit) | W | The power which in one second of time gives rise to one joule of energy.[31] | = 1 W = 1 J/s = 1 N⋅m/s = 1 kg⋅m2/s3 |
Action
Name of unit | Symbol | Definition | Relation to SI units |
---|---|---|---|
atomic unit of action | au | ≡ | ≈ 1.05457168×10−34 J⋅s[35] |
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 |
CGS unit ) |
P | ≡ 1 barye⋅s | = 0.1 Pa⋅s |
pound per foot hour | lb/(ft⋅h) | ≡ 1 lb/(ft⋅h) | ≈ 4.133789×10−4 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 | ≈ 6894.757 Pa⋅s |
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 |
CGS unit ) |
St | ≡ 1 cm2/s | = 10−4 m2/s |
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) |
CGS unit ) |
abamp | ≘ 10 A | = 10 A |
esu per second; CGS unit ) |
esu/s | ≘ (10 A⋅cm/s) / c | ≈ 3.335641×10−10 A |
Electric charge
Name of unit | Symbol | Definition | Relation to SI units |
---|---|---|---|
CGS unit ) |
abC; emu | ≘ 10 C | = 10 C |
atomic unit of charge | au | ≡ e | = 1.602176634×10−19 C |
coulomb | C | ≡ charge of exactly 1/(1.602176634×10−19) elementary charges[36] | = 1 C = 1 A⋅s |
faraday | F | ≡ 1 mol × NA⋅e | ≈ 96485.3383 C |
milliampere hour |
mA⋅h | ≡ 0.001 A × 1 h | = 3.6 C |
CGS unit ) |
statC; Fr; esu | ≘ (10 A⋅cm) / c | ≈ 3.335641×10−10 C |
Electric dipole
Name of unit | Symbol | Definition | Relation to SI units |
---|---|---|---|
atomic unit of electric dipole moment | ea0 | ≈ 8.47835281×10−30 C⋅m[37] | |
coulomb-meter | C⋅m | = 1 C⋅m | |
debye | D | ≡ 10−10 esu⋅Å | ≘ 3.33564095×10−30 C⋅m[38] |
Electromotive force, electric potential difference
Name of unit | Symbol | Definition | Relation to SI units |
---|---|---|---|
CGS unit ) |
abV | ≘ 10−8 V | = 10−8 V |
CGS unit ) |
statV | ≘ c⋅(1 μJ/A⋅m) | = 299.792458 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.[31] | = 1 V = 1 W/A = 1 kg⋅m2/(A⋅s3) = 1 J/C |
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 = 1 kg⋅m2/(A2⋅s3) |
Capacitance
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 = 1 A2⋅s4/(kg⋅m2) |
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 = 1 kg⋅m2/(A⋅s2) |
Magnetic flux density
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 = 1 kg/(A⋅s2) |
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 = 1 kg⋅m2/(A⋅s)2 |
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 + 250 | [K] ≡ [GM] × 125⁄9 + 394.26 |
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
Name of unit | Symbol | Definition | Relation to SI units | Relation to bits |
---|---|---|---|---|
natural unit of information; nit; nepit | nat | |||
shannon | Sh | ≡ ln(2) × nat | ≈ 0.693147 nat | = 1 bit |
hartley; ban | Hart; ban | ≡ ln(10) × nat | ≈ 2.302585 nat | |
bit | bit; b | = 1 bit | ||
nibble | ≡ 4 bits | = 22 bit | ||
byte | B | ≡ 8 bits | = 23 bit | |
kilobyte (decimal) | kB | ≡ 1000 B | = 8000 bit | |
kibibyte (kilobyte ) |
KiB | ≡ 1024 B | = 213 bit = 8192 bit |
Modern standards (such as
Luminous intensity
The candela is the preferred nomenclature for the SI unit.
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 540×1012 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
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 | ≈ 1550.0031 cd/m2 |
candela per square metre (SI unit); nit (deprecated[16]) | cd/m2 | ≡ cd/m2 | = 1 cd/m2 |
footlambert | fL | ≡ (1/π) cd/ft2 | ≈ 3.4262590996 cd/m2 |
lambert | L | ≡ (104/π) cd/m2 | ≈ 3183.0988618 cd/m2 |
stilb (CGS unit)
|
sb | ≡ 104 cd/m2 | = 104 cd/m2 |
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 540×1012 hertz and that has a radiant flux of 1/683 watt.[36] | = 1 lm = 1 cd⋅sr |
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 | ≈ 1550.0031 lx |
lux (SI unit) | lx | ≡ lm/m2 | = 1 lx = 1 lm/m2 |
phot (CGS unit) | ph | ≡ lm/cm2 | = 104 lx |
Radiation
Radiation – source activity
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[42] | = 3.7×1010 Bq |
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
Name of unit | Symbol | Definition | Relation to SI units |
---|---|---|---|
roentgen | R | 1 R ≡ 2.58×10−4 C/kg[34] | = 2.58×10−4 C/kg |
The roentgen is not an SI unit and the NIST strongly discourages its continued use.[44]
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
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 = 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.[46]
Notes
- ^ The technical definition of tropical year is the period of time for the ecliptic longitude of the Sun to increase 360 degrees. (Urban & Seidelmann 2013, Glossary, s.v. year, tropical)
References
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- ^ "NIST Reference on Constants, Units, and Uncertainty."(2010). National Institute of Standards and Technology. Retrieved October 17, 2014.
- ^ a b c d e "NIST - National Institute of Standards and Technology". NIST.
- ^ 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.
- ^ 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.
- ^ "International Astronomical Union - IAU". www.iau.org.
- ^ Klein, Herbert Arthur. (1988). The Science of Measurement: a Historical Survey. Mineola, NY: Dover Publications 0-4862-5839-4.
- ^ Bureau International des Poids et Mesures, 2006, archived from the originalon October 1, 2009, retrieved August 26, 2009
- Bureau International des Poids et Mesures, Section 4.1 Table 8.
- ISBN 0387987460.
- ISBN 978-0-691-13026-2.
- ^ P. Kenneth Seidelmann, Ed. (1992). Explanatory Supplement to the Astronomical Almanac. Sausalito, CA: University Science Books. p. 716 and s.v. parsec in Glossary.
- ^ 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.
- ^ 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. 142–150.
- ^ Pasko, Wesley Washington (1894). American dictionary of printing and bookmaking. (1894). New York: Howard Lockwood. p. 521.
- ^ a b c d e f g h i Rowlett, Russ (2005), How Many? A Dictionary of Units of Measurement
- ^ 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.
- ^ a b c d e US Code of Federal Regulations, Title 21, Section 101.9, Paragraph (b)(5)(viii), archived from the original on August 13, 2009, retrieved August 29, 2009
- ^ Barry N. Taylor, Ed.,NIST Special Publication 330: The International System of Units (SI) (2001 Edition), Washington: US 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".
- ^ CODATA Value: atomic unit of mass. (2010). National Institute of Standards and Technology. Retrieved 29 May 2015.
- ^ The Swiss Federal Office for Metrology gives Zentner on a German language web page "Metas: Masseinheiten - SI-Einheiten". Archived from the original on 2006-09-28. Retrieved 2006-10-09. and quintal on the English translation of that page "OFMET: Units of measure - SI units". Archived from the original on 2001-03-09. Retrieved 2006-10-09.; the unit is marked "spécifiquement suisse !"
- ^ 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.
- ISBN 0-19-850413-6
- ISBN 0-471-29827-1
- ^ "CODATA Value: Planck time". physics.nist.gov. Retrieved 2018-06-20.
- ^ a b Richards, E. G. (2013). "Calendars" in S. E. Urban & P. K. Seidelmann, eds. Explanatory Supplement to the Astronomical Almanac. Mill Valley, CA: University Science Books.
- ^ Richards, E. G. (2013). "Calendars" in S. E. Urban & P. K. Seidelmann, eds. Explanatory Supplement to the Astronomical Almanac. Mill Valley, CA: University Science Books. p. 587.
- ^ Until 1970 the UK Admiralty (and until 1954 the US) used other definitions of the nautical mile and hence the knot. See also #Length
- ^ Tom Benson. (2010.) "Mach Number" Archived 2006-04-10 at the Wayback Machine in Beginner's Guide to Aeronautics. NASA.
- ^ CODATA Value: atomic unit of force. (2006). National Institute of Standards and Technology. Retrieved September 14, 2008.
- ^ a b c d e f g h Comité International des Poids et Mesures, Resolution 2, 1946, retrieved August 26, 2009
- ^ a b c d e f g h i j k l m n o p Barry N. Taylor, (April 1995), Guide for the Use of the International System of Units (SI) (NIST Special Publication 811), Washington, DC: US Government Printing Office, pp. 57–68.
- ^ Barry N. Taylor, (April 1995), Guide for the Use of the International System of Units (SI) (NIST Special Publication 811), Washington, DC: US Government Printing Office, p. 5.
- ^ a b c d e f g "NIST Guide to SI Units, Appendix B.9", Nist, 2 July 2009, retrieved August 27, 2009
- Bureau International des Poids et Mesures, Section 4.1 Table 7.
- ^ BIPM. p. 132. Retrieved May 23, 2019.
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- ISBN 0-12-508345-9, page 677
- American Society for Testing and Materials. Tables A.1 through A.5.
- ^ "Mise en pratique" (PDF). BIPM.
- ^ The NIST Reference on Constants, Units, and Uncertainty, retrieved August 28, 2009
- ^ 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.
- ^ Bureau International des Poids et Mesures, 2006, archived from the originalon June 18, 2007, retrieved August 27, 2009
- ^ "The NIST Guide to the SI (Special Publication 811), section 5.2", Nist, 2008, retrieved August 27, 2009
- ^ 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.
- ^ Comité international des poids et mesures, 2002, Recommendation 2, retrieved August 27, 2009