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 (4°C)	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	~ ?? 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 kW·h	= 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!

See also

• The Unix program units, a useful tool for unit conversion.
• Informal conversion of common units.

• A Dictionary of Units of Measurement
• Frink, a converter, calculator, and programming language
• An online converter
• Various unit converters
• Google, including calculator with unit converter (for the unit converter, type in the first box e.g. "3 mile in km"), calculator help