SI System

The SI system (International System of Units) is the modern metric system of measurement and the dominant system of international commerce and trade. This tool provides comprehensive information about SI base units, derived units, prefixes, and non-SI units accepted for use with SI.

Quantity	Name of Unit	Symbol
Length	metre	m
Mass	kilogram	kg
Time	second	s
Electrical current	ampere	A
Thermodynamic temperature	kelvin	K
Luminous intensity	candela	cd
Amount of substance	mole	mol

Quantity	Name of Unit	Symbol	Expression in SI Base Units	Other Units
Plane angle	radian	rad
Solid angle	steradian	sr
Absorbed radiation	gray	Gy	m2s-2	J/kg
Electrical capacitance	farad	F	m-2 kg-1 s4 A2	C/V
Celsius temperature	degree Celsius	°C	K
Electrical charge	coulomb	C	A s
Electrical conductance	siemens	S	m-2 kg-1 s3 A2	A/V
Electrical inductance	henry	H	m2 kg s-2 A-2
Electrical potential	volt	V	m2 kg s-3 A-1	W/A
Electrical resistance	ohm	Ω	m2 kg s-3 A-2	V/A
Force	newton	N	kg m s-2
Frequency	hertz	Hz	s-1
Illuminance	lux	lx	m-2 cd sr	lm/m2
Luminous flux	lumen	lm	cd sr
Magnetic flux	weber	Wb	m2 kg s-2 A-1	V s
Magnetic flux density	tesla	T	kg s-2 A-1	Wb/m2
Power or radiant flux	watt	W	kg m2 s-3	J/s
Pressure	pascal	Pa	kg/(m s2)	N/m2
Radioactivity	becquerel	Bq	s-1
Work, energy, heat	joule	J	m2 kg s-2	N m
Dose equivalent	sievert	Sv		J/kg
Catalytic activity	katal	kat		mol/s

Power of 10	Prefix	Symbol
1024	yotta	Y
1021	zetta	Z
1018	exa	E
1015	peta	P
1012	tera	T
109	giga	G
106	mega	M
103	kilo	k
102	hecto	h
101	deca	da
10-1	deci	d
10-2	centi	c
10-3	milli	m
10-6	micro	μ
10-9	nano	n
10-12	pico	p
10-15	femto	f
10-18	atto	a
10-21	zepto	z
10-24	yocto	y

Name	Symbol	Value in SI Units
minute	min	1 min = 60 s
hour	h	1 h = 3600 s
day	d	1 d = 86400 s
degree	°	1° = (π/180) rad
liter	L	1 L = 10-3 m3
metric ton	t	1 t = 103 kg
nautical mile	nm	1 nautical mile = 1852 m
knot	knot	1 knot = (1852/3600) m/s
hectare	ha	1 ha = 104 m2
bar	bar	1 bar = 105 Pa
ångström	Å	1 Å = 10-10 m
barn	b	1 b = 10-28 m2