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Metric Units

S.I. Base Units

The International System of Units (S.I.) defines seven base units for the seven base quantities:

Quantity	Name	Symbol
length	meter (or metre)	m
mass	kilogram	kg
time	second	s
electric current	ampere	A
thermodynamic temperature	kelvin	K
luminous intensity	candela	cd
amount of substance	mole	mol

S.I. Derived Units

Derived units are defined in terms of the seven base units.

eg.

area square meter m²

S.I. Derived Units with Special Names

Quantity	Name	Symbol	Derivation
force	newton	N	kg m s^-2
pressure, stress	pascal	Pa	N m^-2
work, energy, quantity of heat	joule	J	N m
power	watt	W	J s^-1
electric charge	coulomb	C	A s
potential difference	volt	V	W A^-1
electromotive force	volt	V	J C^-1
capacitance	farad	F	C V^-1
resistance	ohm		V A^-1
conductance	siemens	S	^-1
magnetic flux	weber	Wb	V s
magnetic flux density, magnetic induction	tesla	T	Wb m^-2
inductance	henry	H	V s A^-1
luminous flux	lumen	lm	cd sr
illumination	lux	lx	lm m^-2
frequency	hertz	Hz	s^-1

S.I. Supplementary Units

Quantity	Name	Symbol	Derivation
area	hectare	ha	10⁴ m²
volume	liter (or litre)	l	10^-3 m³
plane angle	radian	rad
solid angle	steradian	sr

S.I. Prefixes for Multiples and Submultiples

The International System of Units (S.I.) defines 20 prefixes used to form decimal multipliers for the S.I. units:

Prefix	Symbol	Meaning	Prefix	Symbol	Meaning
yotta	Y	10²⁴	milli	m	10^-3
zetta	Z	10²¹	micro	µ	10^-6
exa	E	10¹⁸	nano	n	10^-9
peta	P	10¹⁵	pico	p	10^-12
tera	T	10¹²	femto	f	10^-15
giga	G	10⁹	atto	a	10^-18
mega	M	10⁶	zepto	z	10^-21
kilo	k	10³	yocto	y	10^-24

hecto	h	10²	deci	d	10^-1
deca	da	10	centi	c	10^-2

eg.
cm = 10^-2 m = 0.01 m
km = 10³ m = 1000 m

Note:
The kilogram is the only S.I. base unit that already includes a prefix.
Therefore 1 gram (g) = 0.001 kilogram (kg).