Meter (m) for length: The length of the path traveled by light in a vacuum during a time interval of 1/299,792,458 of a second.

Kilogram (kg) for mass: Equal to the mass of the international prototype of the kilogram.

Second (s) for time: The duration of 9,192,631,770 periods of radiation corresponding to the transition between the two hyperfine levels of the ground state of the cesium 133 atom.

Ampere (A) for electric current: A constant current which, if maintained in two straight parallel conductors of infinite length, of negligible circular cross-section, and placed 1 meter apart in a vacuum, would produce between these conductors a force equal to 2 x 10^-7 newton per meter of length.

Kelvin (K) for thermodynamic temperature: The fraction 1/273.16 of the thermodynamic temperature of the triple point of water.

Candela (cd) for luminous intensity: A source that emits monochromatic radiation of frequency 540 x 10¹² hertz and that has a radiant intensity in that direction of 1/683 watt per steradian.

Mole (mol) for quantity of matter: The amount of substance of a system which contains as many elementary entities as there are atoms in 0.012 kilogram of carbon 12.

Ångström (Å) for measure of displacement: Equal to 0.0000000001 meter (10^-10m). Used to express wavelengths of visible light, UV light, gamma rays, and x-rays.

Liter (L) for volume: Equal to 1000 cm^3.

Derived Quantity	Name	Symbol	Expression in Terms of Other SI Units	Expression in Terms of SI Base Units
plane angle	radian	rad	-	m·m-1=1
solid angle	steradian	sr	-	m2·m-2=1
frequency	hertz	Hz	-	s-1
force	newton	N	-	m·kg·s-2
pressure, stress	pascal	Pa	N/m2	m-1·kg·s-2
energy, work, quantity of heat	joule	J	Nm	m2·kg·s-2
power, radiant flux	watt	W	J/s	m2·kg·s-3
electric charge, quantity of electricity	coulomb	C	-	s·A
electric potential, difference, electromotive force	volt	V	W/A	m2·kg·s-3·A-1
capacitance	farad	F	C/V	m-2·kg-1·s4·A2
electric conductance	siemens	S	A/V	m-2·kg-1·s3·A2
electric resistance	ohm	W	V/A	m2·kg·s-3·A-2
magnetic flux	weber	Wb	Vs	m2·kg·s-2·A-1
magnetic flux density	tesla	T	Wb/m2	kg·s-2·A-1
inductance	henry	H	Wb/A	m2·kg·s-2·A-2
Celsius temperature	degree Celsius	°C	-	K
luminous flux	lumen	lm	cd·sr	m2·m-2·cd = cd
illuminance	lux	lx	lm/m2	m2·m-4·cd = m-2·cd
activity (of a radionuclide)	becquerel	Bq	-	s-1
absorbed dose, specific energy (imparted), kerma	gray	Gy	J/kg	m2·s-2
dose equivalent	sievert	Sv	J/kg	m2·s-2
catalytic activity	katal	kat	-	s-1mol

 

Prefix		Symbol	Factor	Decimal
Yocto	Septillion	y	10-24		0.000000000000000000000001
Zepto	Sextillion	z	10-21		0.000000000000000000001
Atto	Quintillionth	a	10-18		0.000000000000000001
Femto	Quadrillionth	f	10-15		0.000000000000001
Pico	Trillionth	p	10-12		0.000000000001
Nano	Billionth	n	10-9		0.000000001
Micro	Millionth	µ	10-6		0.000001
Milli	Thousandth	m	10-3		0.001
Centi	Hundredth	c	10-2		0.01
Deci	Tenth	d	10-1		0.1
Base Unit	One		100	1
Deca	Ten	da	101	10
Hecto	Hundred	h	102	100
Kilo	Thousand	k	103	1 000
Mega	Million	M	106	100 0000
Giga	Billion	G	109	1000 000 000
Tera	Trillion	T	1012	1000 000 000 000
Peta	Quadrillion	P	1015	1 000 000 000 000 000
Exa	Quintillion	E	1018	1 000 000 000 000 000 000
Zetta	Sextillionth	Z	1021	1 000 000 000 000 000 000 000
Yotta	Septillionth	Y	1024	1 000 000 000 000 000 000 000 000

 

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