Conversion of units

This article lists conversion factors between a number of units.

Name of unit Symbol Relation to SI units
Length, l
meter (SI base unit) m  
micron μ = μm = 10-6 m
ångström Å = 10-10 m
bohr (au) a0, b ~ 5.291 77 × 10-11 m
x unit X ~ 1.002 × 10-13 m
Fermi   = 1×10-15 m
inch in = 2.54 × 10-2 m
foot ft = 12 in = 0.3048 m
yard yd = 3 ft = 0.9144 m
mile mi = 1760 yd = 1609.344 m
nautical mile   = 1852 m ~ 6076.1 feet
geographical mile   = 1855 m = 6087.15 feet
astronomical unit AU = 1.495 978 706 6 × 1011 m
parsec pc = 3.085 677 580 666 31 × 1016 m
light year l.y. = 9.460 730 473 × 1015 m
light second   = 2.997 924 58 × 108 m
mil   = 1×10-3 in = 2.54 ×10-5 m m
Rod   = 5.029 210 058 42 m
Chain   = 20.116 840 233 7 m
Fathom   = 1.8288 m
Area, A
square metre (SI unit) m2  
barn b 10-28 m2
acre   ~ 4046.856 m2
are a = 100 m2
hectare ha = 104 m2
Volume, V
cubic metre (SI unit) m3  
litre l, L = dm3 = 10-3 m3
lambda λ = μl = 10-6 dm3
barrel (US)   ~ 158.987 dm3
gallon (US) gal (US) ≅ 3.785 41 dm3
gallon (UK) gal (UK) = 4.546 09 dm3
fluid ounce (US) fl. oz. (US) ≅ 29.57 ml
fluid ounce (Imperial) fl. oz. (Imp.) ≅ 28.41 ml
Mass, m
kilogram (SI base unit) kg  
electron mass (au) me ~ 9.109 39 × 10-31 kg
unified atomic mass unit, dalton u, Da ~ 1.660 540 × 10-27 kg
gamma γ = μg
tonne t = 103 kg
pound (avoirdupois) lb, in physics "lbm" = 0.453 592 37 kg
ounce (avoirdupois) oz ~ 28.349 5 g
ounce (troy) oz (troy) ~ 31.103 5 g
grain gr = 64.798 91 mg
Time, t
second (SI base unit) s  
au of time   ~ 2.418 88 × 10-17 s
minute min = 60 s
hour h = 3600 s
day d = 86 400 s (not exactly defined due to leap seconds)
year a ~ 31 556 952 s
svedberg Sv ~ 10-13 s
Acceleration, a
(SI unit) m·s-2  
standard acceleration of free fall gn = 9.806 65 m·s-2
galileo Gal = 10-2 m·s-2
Force, F
newton (SI unit) N = kg·m·s-2
dyne (cgs unit) dyn = 10-5N
au of force   ~ 8.238 73 × 10-8N
pound-force lbf ≅ 4.448 22 N
kilogram-force kgf = 9.806 65 N
Pressure, p
pascal (SI unit) Pa = N·m-2 = kg·m-1·s-2
atmosphere atm = 101 325 Pa
bar bar = 105 Pa
torr Torr = (101 325/760) Pa ~ 133.322 Pa
millimetre of mercury (conventional) mmHg = 13.5951 × 980.655 × 10-2 Pa ~ 133.322 Pa (= 1 torr)
millimetre of water (4C) mm H2O = 9.806 38 Pa
pounds per square inch psi ~ 6.894 757 × 103 Pa
Electric current, I
ampere (SI base unit) A  
esu per second (cgs unit) esu.s-1 ~ ?? A
electromagnetic unit (cgs unit) abamp 10 A
Electric charge, Q
coulomb (SI unit) C = A.s
statcoulomb, electrostatic unit (cgs unit) statC, esu ~ 3.335 6 × 10-10 C
Voltage, Electromotive force, U
volt (SI unit) V = N·m·C-1
statvolt (cgs unit) statV =299.792458 V
Electrical resistance, R
ohm (SI unit) ohm = V·A-1
Energy, U
joule (SI unit) J = N·m = kg·m2·s-2
erg (cgs unit) erg = 10-7 J
hartee (au) Eh ~ 4.359 75 × 10-18 J
rydberg Ry ~ 2.179 87 × 10-18 J
electronvolt eV = e × V ~ 1.602 18 × 10-19 J
calorie, thermochemical calth = 4.184 J
calorie, international calIT = 4.1868 J
15 °C calorie calIT ~ 4.1855 J
litre atmosphere l atm = 101.325 J
British thermal unit Btu ≅ 1055.06 J
Board of Trade Unit or kilowatt-hour B.O.T.U. or kWh = 3.6 × 106 J
Power, P
watt (SI unit) W = J·s-1 = N·m·s-1 = kg·m2·s-3
horsepower hp ≅ 745.7 W
Action, Angular momentum, L, J
SI unit J·s = N·m·s = kg·m2·s-1
cgs unit erg·s = 10-7 J·s
au of action h = h/2&pi ≅ 1.054 57 × 10-34 J·s
Dynamic viscosity, η
SI unit Pa·s = N·m-2·s = kg·m-1·s-1
poise P = 10-1Pa·s
centipoise cP = mPa·s
Kinematic viscosity, ν
SI unit m2·s-1  
stokes St = 10-4m2·s-1
Temperature, T
kelvin (SI base unit) K  
degree Celsius °C T[°C] = T[K] - 273.15
degree Fahrenheit °F T [°F] = 1.8 (T [°C]) + 32
degree Rankine °R = (5/9) K

Note that lbm is pound mass, not pound meter!

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