SI derived unit

SI derived units are part of the SI system of measurement units and are derived from the seven SI base units.

Note that while the names of all SI units are in lowercase, the symbols of units named after people are written with an initial capital letter (eg: meter, m; hertz, Hz). The exception is degrees Celsius, which refers to degrees on the Celsius scale.

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Contents 1 Derived units with special names 2 Other quantities and units 3 See also 4 References

Derived units with special names

Base units can be put together to derive units of measurement for other quantities. In addition to the two dimensionless derived units radian (rad) and steradian (sr) there are 20 derived units having special names:

Named units derived from SI base units

Name	Symbol	Quantity	Expression in terms of other units	Expression in terms of SI base units
hertz	Hz	frequency	1/s	s-1
radian	rad	angle	m∙m-1	dimensionless
steradian	sr	solid angle	m2∙m-2	dimensionless
newton	N	force, weight	m∙kg/s2	m∙kg∙s−2
pascal	Pa	pressure, stress	N/m2	m−1∙kg∙s−2
joule	J	energy, work, heat	N∙m = C·V = W·s	m2∙kg∙s−2
watt	W	power, radiant flux	J/s = V·A	m2∙kg∙s−3
coulomb	C	electric charge or electric flux	s∙A	s∙A
volt	V	voltage, electrical potential difference, electromotive force	W/A = J/C	m2∙kg∙s−3∙A−1
farad	F	electric capacitance	C/V	m−2∙kg−1∙s4∙A2
ohm	Ω	electric resistance, impedance, reactance	V/A	m2∙kg∙s−3∙A−2
siemens	S	electrical conductance	1/Ω	m−2∙kg−1∙s3∙A2
weber	Wb	magnetic flux	J/A	m2∙kg∙s−2∙A−1
tesla	T	magnetic field strength, magnetic flux density	V∙s/m2 = Wb/m2 = N/(A∙m)	kg∙s−2∙A−1
henry	H	inductance	V∙s/A = Wb/A	m2∙kg∙s−2∙A−2
degree Celsius	°C	temperature	K − 273.15	K − 273.15
lumen	lm	luminous flux	lx·m2	cd·sr
lux	lx	illuminance	lm/m2	m−2∙cd∙sr
becquerel	Bq	radioactivity (decays per unit time)	1/s	s−1
gray	Gy	absorbed dose (of ionizing radiation)	J/kg	m2∙s−2
sievert	Sv	equivalent dose (of ionizing radiation)	J/kg	m2∙s−2
katal	kat	catalytic activity	mol/s	s−1∙mol

Note that other units such as the litre are not SI units, but are accepted for use with SI. See non-SI units accepted for use with SI.

Other quantities and units

Compound units derived from SI units
Name	Symbol	Quantity	Expression in terms of SI base units
square metre	m2	area	m2
cubic metre	m3	volume	m3
metre per second	m/s	speed, velocity	m·s−1
cubic metre per second	m3/s	volumetric flow	m3·s−1
metre per second squared	m/s2	acceleration	m·s−2
metre per second cubed	m/s3	jerk, jolt	m·s−3
metre per quartic second	m/s4	snap	m·s−4
radian per second	rad/s	angular velocity	s−1
newton second	N·s	momentum, impulse	kg·m·s−1
newton metre second	N·m·s	angular momentum	kg·m2·s−1
newton metre	N·m	torque, moment of force	kg·m2·s−2
reciprocal metre	m−1	wavenumber	m−1
kilogram per cubic metre	kg/m3	density, mass density	kg·m−3
cubic metre per kilogram	m3/kg	specific volume	kg−1·m3
mole per cubic metre	mol/m3	amount (-of-substance) concentration	m−3·mol
cubic metre per mole	m3/mol	molar volume	m3·mol−1
joule per kelvin	J/K	heat capacity, entropy	kg·m2·s−2·K−1
joule per kelvin mole	J/(K·mol)	molar heat capacity, molar entropy	kg·m2·s−2·K−1·mol−1
joule per kilogram kelvin	J/(K·kg)	specific heat capacity, specific entropy	m2·s−2·K−1
joule per mole	J/mol	molar energy	kg·m2·s−2·mol−1
joule per kilogram	J/kg	specific energy	m2·s−2
joule per cubic metre	J/m3	energy density	kg·m−1·s−2
newton per metre	N/m = J/m2	surface tension	kg·s−2
watt per square metre	W/m2	heat flux density, irradiance	kg·s−3
watt per metre kelvin	W/(m·K)	thermal conductivity	kg·m·s−3·K−1
square metre per second	m2/s	kinematic viscosity, diffusion coefficient	m2·s−1
pascal second	Pa·s = N·s/m2	dynamic viscosity	kg·m−1·s−1
coulomb per cubic metre	C/m3	electric charge density	m−3·s·A
ampere per square metre	A/m2	electric current density	A·m−2
siemens per metre	S/m	conductivity	kg−1·m−3·s3·A2
siemens square metre per mole	S·m2/mol	molar conductivity	kg-1·s3·mol−1·A2
farad per metre	F/m	permittivity	kg−1·m−3·s4·A2
henry per metre	H/m	permeability	kg·m·s−2·A−2
volt per metre	V/m	electric field strength	kg·m·s−3·A−1
ampere per metre	A/m	magnetic field strength	A·m−1
candela per square metre	cd/m2	luminance	cd·m−2
coulomb per kilogram	C/kg	exposure (X and gamma rays)	kg−1·s·A
gray per second	Gy/s	absorbed dose rate	m2·s−3
ohm metre	Ω·m	resistivity	kg·m3·s−3·A−2
kilometres per hour	km/h	speed, velocity	3.6-1·m·s-1
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See also

• Planck units
• SI prefix

References

• I. Mills, Tomislav Cvitas, Klaus Homann, Nikola Kallay, IUPAC: Quantities, Units and Symbols in Physical Chemistry, 2nd edition (June 1993), Blackwell Science Inc (p. 72)

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