| Name of unit |
Symbol |
Relation to SI units |
|
Length, l
|
| metre (SI base unit) |
m |
1 |
| fermi |
fm |
≡ 10-15m |
| x unit; siegbahn |
xu |
≈ 1.0021×10-13m |
| Bohr radius |
a0; b |
≡ α/(4πR∞) ≈ 5.291 772 083×10-11 ± 19×10-20 m |
| atomic unit of
length |
au |
≡ a0 ≈ 5.291 772 083×10-11 ± 19×10-20 m |
| ångström |
Å |
≡ 10-10m = 0.1 nm |
| micron |
μ |
≡ 10-6m = 1 μm |
| mil; thou |
mil |
≡ 10-3 in = 2.54×10-5 m |
| inch |
in |
≡ 0.0254 m = 25.4 mm |
| foot |
ft |
≡ 12 in = 0.3048 m |
| yard |
yd |
≡ 3 ft = 0.9144 m |
| fathom |
fm |
≡ 6 ft = 1.8288 m
(sometimes ≡ 1/1000 NM = 1.852 m) |
| rod |
rd |
≡ 16 1/2 ft = 5,0292 m |
| chain (Gunter's) |
ch |
≡ 66 ft = 20.1168 m |
| chain (Ramden's; Engineer's) |
ch |
≡ 100 ft = 30.48 m |
| mile |
mi |
≡ 1760 yd = 5280 ft = 1609.344 m |
| nautical mile |
NM |
≡ 1852 m |
| geographical mile |
mi |
≡ 1855 m or
≡6082 ft = 1853.7936 m |
| light second |
|
≡ 2.997 924 58×108 m |
| astronomical unit |
AU |
= 149 597 870.691 ± 0.030 km |
| light year |
l.y. |
≡ c0×86 400×365.25
= 9.460 730 472 580 8×1015 m |
| parsec |
pc |
≈ 180×60×60/π AU
≈ 206 264.806 25 AU
= 3.261 563 776 9 ± 6×10-10 light-years
= 3.085 677 581 3×1016 ± 6×106 m |
|
|
| square metre (SI unit) |
m2 |
1 |
| barn |
b |
≡ 10-28 m2 |
| are |
a |
≡ 100 m2 |
| hectare |
ha |
≡ 10 000 m2 = 0.01 km2 |
| acre |
ac |
≡ 10 sq ch = 4840 sq yd = 4046.856 422 4 m2 |
|
|
| cubic metre (SI unit) |
m3 |
≡ 1 |
| litre |
L |
≡ 1 dm3 |
| lambda |
λ |
≡ 1 mm3 = 1 μL |
| dram (Imperial fluid); Imperial fluidram |
fl dr |
≡ 1/8 fl oz = 3.551 632 812 5 mL |
| dram (U.S. fluid); U.S. fluidram |
fl dr |
≡ 1/8 US fl oz = 3.696 691 195 312 5 mL |
| teaspoon (Canadian) |
tsp |
≡ 1/6 fl oz ≈ 4.735 510 416 667 mL |
| teaspoon (U.S.) |
tsp |
≡ 1/6 US fl oz = 4.928 921 593 75 mL |
| teaspoon (metric) |
|
≡ 5 mL |
| tablespoon (Canadian) |
tbsp |
≡ 1/2 fl oz = 14.206 531 25 mL |
| tablespoon (U.S.) |
tbsp |
≡ 1/2 US fl oz = 14.786 764 781 25 mL |
| tablespoon (metric) |
|
≡ 15 mL |
| cubic inch |
cu in |
≡ 1 in3 = 16.387 064 mL |
| tablespoon (Imperial) |
tbsp |
≡ 5/8 fl oz = 17.758 164 062 5 mL |
| fluid ounce (Imperial) |
fl oz (Imp) |
≡ 1/160 gal (Imp) = 28.413 062 5 mL |
| fluid ounce (U.S.) |
fl oz (US) |
≡ 1/128 gal (US) = 29.573 529 562 5 mL |
| pint (U.S. fluid) |
pt (US fl) |
≡ 1/8 gal (US) = 473.176 473 mL |
| pint (U.S. dry) |
pt (US dry) |
≡ 1/4 bu (US lvl) = 550.610 471 357 5 mL |
| pint (Imperial) |
pt (Imp) |
≡ 1/8 gal (Imp) = 568.261 25 mL |
| quart (U.S. fluid) |
qt (US) |
≡ 1/4 gal (US fl) = 0.946 352 946 L |
| quart (U.S. dry) |
qt (US) |
≡ 1/32 bu (US lvl) = 1/4 gal (US dry) = 1.101 220 942 715 L |
| quart (Imperial) |
qt (Imp) |
≡ 1/4 gal (Imp) = 1.136 522 5 L |
| gallon (U.S. fluid) |
gal (US) |
≡ 231 cu in = 3.785 411 784 L |
| gallon (U.S. dry) |
gal (US) |
≡ 1/8 bu (US lvl) = 4.404 883 770 86 L |
| gallon (Imperial) |
gal (Imp) |
≡ 4.546 09 L |
| cubic foot |
cu ft |
≡ 1728 cu in = 28.316 846 592 L |
| bushel (U.S. dry level) |
bu (US lvl) |
≡ 2150.42 cu in = 35.239 070 166 88 L |
| bushel (Imperial) |
bu (Imp) |
≡ 8 gal (Imp) = 36.368 72 L |
| bushel (U.S. dry heaped) |
bu (US) |
≡ 1 1/4 bu (US lvl) = 44.048 837 708 6 L |
| barrel (U.S. oil) |
bl |
≡ 42 gal (US) = 158.987 294 928 L |
| barrel (Imperial) |
bl (Imp) |
≡ 36 gal (Imp) = 163.659 24 L |
| cubic yard |
cu yd |
≡ 27 cu ft = 0.764 554 857 984 m3 |
| freight ton |
|
≡ 40 cu ft = 1.132 673 863 68 m3 |
| load |
|
≡ 50 cu ft = 1.415 842 329 6 m3 |
| register ton |
|
≡ 100 cu ft = 2.831 684 659 2 m3 |
|
|
| radian |
rad |
≡ 1 m/m |
| centesimal second of arc |
" |
≡ 1 gr/10000 ≈ 1.570 796 µrad |
| second of arc |
" |
≡ 1°/3600 ≈ 4.848 137 µrad |
| centesimal minute of arc |
' |
≡ 1 gr/100 ≈ 0.157 080 mrad |
| minute of arc |
' |
≡ 1°/60 ≈ 0.290 888 mrad |
| angular mil |
µ |
≡ 2π/6400 rad ≈ 0.981 748 mrad |
| gradian; gon |
gr |
≡ 2π/400 rad = 0.9° ≈ 15.707 963 mrad |
| degree (of arc) |
° |
≡ π/180 rad ≈ 17.453 293 mrad |
| sign |
|
≡ 30° ≈ 0.523 599 rad |
| octant |
|
≡ 45° ≈ 0.785 398 rad |
| sextant |
|
≡ 60° ≈ 1.047 198 rad |
| quadrant |
|
≡ 90° ≈ 1.570 796 rad |
|
|
| kilogram |
kg |
(SI base unit) |
| electron rest mass |
me |
≈ 9.109 381 88×10-31 ± 72×10-39 kg |
| atomic unit of
mass |
au |
≡ me ≈ 9.109 381 88×10-31 ± 72×10-39 kg |
| unified atomic mass unit; dalton |
u; Da |
≈ 1.660 538 73×10-27 ± 13×10-35 kg |
| gamma |
γ |
≡ 1 μg |
| grain |
gr |
≡ 64.798 91 mg |
| carat (metric) |
kt |
≡ 200 mg |
| carat |
kt |
≡ 3 1/6 gr ≈ 205.196 548 333 mg |
| ounce (avoirdupois) |
oz |
≡ 1/16 lb = 28.349 523 125 g |
| ounce (troy) |
oz (troy) |
≡ 31.103 476 8 g |
| pound (avoirdupois) |
lb ("lbm" in physics) |
≡ 7000 gr = 0.453 592 37 kg |
| short hundredweight; cental |
sh cwt |
≡ 100 lb av = 45.359 237 kg |
| long hundredweight |
long cwt |
≡ 112 lb av = 50.802 345 44 kg |
| quintal (metric) |
|
≡ 100 kg |
| short ton |
sh tn |
≡ 2000 lb = 907.184 74 kg |
| tonne |
t |
≡ 1000 kg |
| long ton |
long tn |
≡ 2240 lb = 1016.046 908 8 kg |
|
|
| second |
s |
(SI base unit) |
| Planck time |
|
≡ √Gh/c5 ≈ 1.351 211 818×10-43 s |
| atomic unit of
time |
au |
≡ a0/(α·c) ≈ 2.418
884 254×10-17 s |
| svedberg |
S |
≡ 10-13 s = 100 fs |
| shake |
|
≡ 10-8 s = 10 ns |
| sigma |
|
≡ 10-6 s = 1 μs |
| jiffy |
|
≡ 1/60 s ≈ 16.666 667 ms (sometimes ≡ 1/100 s = 10 ms) |
| minute |
min |
≡ 60 s |
| hour |
h |
≡ 60 min = 3600 s |
| day |
d |
≡ 24 h = 86 400 s |
| week |
wk |
≡ 7 d = 604 800 s |
| fortnight |
|
≡ 2 wk = 1 209 600 s |
| month (hollow) |
mo |
≡ 29 d = 2 505 600 s |
| month (full) |
mo |
≡ 30 d = 2 592 000 s |
| year (Calendar) |
a |
≡ 365 d = 31 536 000 s |
| year (Gregorian) |
a |
≡ 365.2425 d = 31 556 952 s |
| year (Julian) |
a |
≡ 365.25 d = 31 557 600 s |
| lustre; lustrum |
|
≡ 5 a of 365 d = 1.5768×108 s |
| octaeteris |
|
≡ 8 a of 365 d = 2.522 88×108 s |
| decade |
|
≡ 10 a of 365 d = 3.1536×108 s |
| enneadecaeteris; Metonic cycle |
|
≡ 110 mo (hollow) + 125 mo (full) = 19 a of 365 d = 5.996 16×108 s |
| Callippic cycle |
|
≡ 441 mo (hollow) + 499 mo (full) = 76 a of 365.25 d = 2.398 377 6×109 s |
| century (Calendar) |
|
≡ 100 a of 365 d = 3.1536×109 s |
| century (Julian) |
|
≡ 100 a of 365.25 d = 3.155 76×109 s |
| Hipparchic cycle |
|
≡ 4 Callippic cycles - 1 d = 9.593 424×109 s |
| millennium (Calendar) |
|
≡ 1000 a of 365 d = 3.1536×1010 s |
| millennium (Gregorian) |
|
≡ 1000 a of 365.2425 d = 3.155 695 2×1010 s |
| millennium (Julian) |
|
≡ 1000 a of 365.25 d = 3.155 76×1010 s |
| Sothic cycle |
|
≡ 1461 a of 365 d = 4.607 409 6×1010 s |
|
|
| metre per second |
m/s |
≡ 1 m/s |
| foot per hour |
fph |
≡ 1 ft/h ≈ 8.466 667×10-5 m/s |
| furlong per fortnight |
|
≈ 1.663 095×10-4 m/s |
| inch per minute |
ipm |
≡ 1 in/min ≈ 4.23 333×10-4 m/s |
| foot per minute |
fpm |
≡ 1 ft/min = 5.08×10-3 m/s |
| inch per second |
ips |
≡ 1 in/s = 2.54×10-2 m/s |
| kilometre per hour |
km/h |
≡ 1 km/h ≈ 2.777 778×10-1 m/s |
| foot per second |
fps |
≡ 1 ft/s = 3.048×10-1 m/s |
| mile per hour |
mph |
≡ 1 mi/h = 0.447 04 m/s |
| statute mile per hour |
mph |
≈ 0.447 041 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 ≈ 0.514 773 m/s |
| mile per minute |
mpm |
≡ 1 mi/min = 26.8224 m/s |
| mile per second |
mps |
≡ 1 mi/s = 1.609 344 km/s |
| speed of light in vacuum |
c |
≡ 2.997 924 58×108 m/s |
|
|
| metre per second squared |
m/s² |
≡ 1 m/s² |
| foot per hour per second |
fph/s |
≡ 1 ft/h·s ≈ 8.466 667×10-5 m/s² |
| inch per minute per second |
ipm/s |
≡ 1 in/min·s ≈ 4.233 333×10-4 m/s² |
| foot per minute per second |
fpm/s |
≡ 1 ft/min·s = 5.08×10-3 m/s² |
| galileo |
Gal |
≡ 1 cm/s² = 0.01 m/s² |
| inch per second squared |
ips² |
≡ 1 in/s² = 2.54×10-2 m/s² |
| foot per second squared |
fps² |
≡ 1 ft/s² = 3.048×10-1 m/s² |
| mile per hour per second |
mph/s |
≡ 1 mi/h·s = 4.4704×10-1 m/s² |
| knot per second |
kn/s |
≡ 1 kn/s ≈ 5.144 444×10-1 m/s² |
| standard gravity |
g |
≡ 9.806 65 m/s² |
| mile per minute per second |
mpm/s |
≡ 1 mi/min·s = 26.8224 m/s² |
| mile per second squared |
mps² |
≡ 1 mi/s² = 1.609 344×103 m/s² |
|
|
| newton (SI unit) |
N |
≡ kg·m/s² |
| atomic unit of
force |
au |
≡ me·α²·c²/a0 ≈ 8.238 722 241×10-8 N |
| dyne (cgs unit) |
dyn |
≡ g·cm/s² = 10-5 N |
| gravet |
|
≡ g × 1 g = 9.806 65 mN |
| poundal |
pdl |
≡ 1 lb·ft/s² = 0.138 254 954 376 N |
| ounce-force]] |
ozf |
≡ g × 1 oz = 0.278 013 850 953 781 2 N |
| pound-force |
lbf |
≡ g × 1 lb = 4.448 221 615 260 5 N |
| kilogram-force; kilopond; grave |
kgf; kp |
≡ g × 1 kg = 9.806 65 N |
| sthene (mts unit) |
sn |
≡ 1 t·m/s² = 1 kN |
| kip-force |
kipf |
≡ g × 1 kip = 4.448 221 615 260 5 kN |
| ton-force |
tnf |
≡ g × 1 sh tn = 8.896 443 230 521 kN |
|
|
| pascal (SI unit) |
Pa |
≡ N/m² = kg/m·s² |
| barye (cgs unit) |
|
≡ 1 dyn/cm² = 0.1 Pa |
| poundal per square foot |
pdl/sq ft |
≡ 1 pdl/sq ft ≈ 1.488 164 Pa |
| millimetre of water (4°C) |
mmH2O |
≡ 1000 kg/m³ × 1 mm × g = 9.806 65 Pa (= 1 kgf/m²) |
| pound per square foot |
psf |
≡ 1 lb/sq ft × g ≈ 47.880 259 Pa |
| centimetre of water (4°C) |
cmH2O |
≡ 1000 kg/m³ × 1 cm × g = 98.0665 Pa |
| torr |
torr |
≡ (101 325/760) Pa ≈ 133.322 Pa |
| millimetre of mercury (conventional) |
mmHg |
≈ 13 595.1 kg/m³ × 1 mm × g ≈ 133.322 Pa (= 1 torr) |
| inch of water (4°C) |
inH2O |
≡ 1000 kg/m³ × 1 in × g = 249.088 91 Pa |
| pièze (mts unit) |
pz |
≡ 1000 kg/m·s² = 1 kPa |
| centimetre of mercury |
cmHg |
≈ 13 595.1 kg/m³ × 1 cm × g ≈ 1.333 224 kPa (= 10 torr) |
| foot of water (4°C) |
ftH2O |
≡ 1000 kg/m³ × 1 ft × g = 2.989 066 92 kPa |
| inch of mercury |
inHg |
≈ 13 595.1 kg/m³ × 1 in × g ≈ 3.386 388 kPa |
| pound per square inch |
psi |
≡ 1 lb × g / 1 sq in ≈ 6.894 757×103 Pa |
| foot of mercury |
ftHg |
≈ 13 595.1 kg/m³ × 1 ft × g ≈ 40.636 658 kPa |
| ton per square foot |
|
≡ 1 sh tn × g / 1 sq ft ≈ 95.760 518 kPa |
| atmosphere (technical) |
atm |
≡ 1 kgf/cm² = 98.0665 kPa |
| bar |
bar |
≡ 105 Pa |
| atmosphere (standard) |
atm |
≡ 101 325 Pa |
| kip per square inch |
ksi |
≡ 1 kip/sq in ≈ 703.069 580 kPa |
| kilogram-force per square millimetre |
kgf/mm² |
≡ 1 kgf/mm² = 9.806 65 MPa |
|
|
| joule (SI unit) |
J |
≡ N·m = kg·m²/s² |
| electronvolt |
eV |
≡ e × 1 V = 1/6.241 509 629 152 65×1018 J ≈ 1.602 176×10-19 J |
| rydberg |
Ry |
≡ R∞·h·c ≈ 2.179 872×10-18 J |
| hartree |
Eh |
≡ me·α²·c² ≈ 4.359 744×10-18 J (= 2Ry) |
| atomic unit of
energy |
au |
≡ Eh ≈ 4.359 744×10-18 J |
| erg (cgs unit) |
erg |
≡ 1 g·cm²/s² = 10-7 J |
| foot-poundal |
ft pdl |
≡ 1 ft·pdl = 4.214 011 009 380 48×10-2 J |
| cubic centimetre of atmosphere; standard cubic centimetre |
cc atm; scc |
≡ 1 atm × 1 cm³ = 0.101 325 J |
| inch-pound force |
in lbf |
≡ g × 1 lb × 1 in = 0.112 984 829 027 616 7 J |
| foot-pound force |
ft lbf |
≡ g × 1 lb × 1 ft = 1.355 817 948 331 400 4 J |
| calorie (20°C) |
cal20°C |
≈ 4.1819 J |
| calorie (thermochemical) |
calth |
≡ 4.184 J |
| calorie (15°C) |
cal15°C |
≡ 4.1855 J |
| calorie (International Table) |
calIT |
≡ 4.1868 J |
| calorie (mean) |
calmean |
≈ 4.190 02 J |
| calorie (4°C) |
cal4°C |
≈ 4.2045 J |
| litre of atmosphere; standard
litre |
l atm; sl |
≡ 1 atm × 1 L = 101.325 J |
| gallon of atmosphere (U.S.) |
gal atm |
≡ 1 atm × 1 gal (US) = 383.556 849 013 8 J |
| gallon of atmosphere (Imperial) |
gal atm |
≡ 1 atm × 1 gal (Imp) = 460.632 569 25 J |
| British thermal unit (thermochemical) |
BTUth |
≡ 1 lb/g × 1 calth × 1 °F/°C ≈ 1.054 350 kJ |
| British thermal unit (59°F) |
BTU59°F |
≡ 1.054 804 kJ |
| British thermal unit (International Table) |
BTUIT |
≡ 1 lb/g × 1 calIT × 1 °F/°C = 1.055 055 852 62 kJ |
| British thermal unit (mean) |
BTUmean |
≈ 1.055 87 kJ |
| Celsius heat unit (International Table) |
CHUIT |
≡ 1 BTUIT × 1 °C/°F = 1.899 100 534 716 kJ |
| cubic foot of atmosphere; standard cubic foot |
cu ft atm; scf |
≡ 1 atm × 1 cu ft = 2.869 204 480 934 4 kJ |
| kilocalorie; large calorie |
kcal; Cal |
≡ 1000 calIT = 4.1868 kJ |
| cubic yard of atmosphere; standard cubic yard |
cu yd atm; scy |
≡ 1 atm × 1 cu yd = 77.468 520 985 228 8 kJ |
| cubic foot of natural gas |
|
≡ 1000 BTUIT = 1.055 055 852 62 MJ |
| horsepower-hour |
hph |
≡ 1 hp (electrical imperial) × 1 h = 2.6856 MJ |
| Board of Trade Unit; kilowatt-hour |
B.O.T.U.; kWh |
≡ 1 kW × 1 h = 3.6 MJ |
| thermie |
th |
≡ 1 McalIT = 4.1868 MJ |
| therm (U.S.) |
|
≡ 100 000 BTU59°F = 105.4804 MJ |
| therm (E.C.) |
|
≡ 100 000 BTUIT = 105.505 585 262 MJ |
| ton of TNT |
tTNT |
≡ 1 Gcalth = 4.184 GJ |
| barrel of oil equivalent |
bboe |
≈ 5.8 MBTU59°F ≈ 6.12 GJ |
| ton of coal equivalent |
TCE |
≡ 7 Gcalth = 29.3076 GJ |
| ton of oil equivalent |
TOE |
≡ 10 Gcalth = 41.868 GJ |
| quad |
|
≡ 1015 BTUIT = 1.055 055 852 62 EJ |