Prefixes for SI Units and Derived SI Units

Prefix--------

Symbol

-------------------------------------Factor-------------------

---------------

----------

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yotta	Y	1 000 000 000 000 000 000 000 000	= 10 24	(e+24)
zetta	Z	1 000 000 000 000 000 000 000	= 10 21	(e+21)
exa	E	1 000 000 000 000 000 000	= 10 18	(e+18)
peta	P	1 000 000 000 000 000	= 10 15	(e+15)
tera	T	1 000 000 000 000	= 10 12	(e+12)
giga	G	1 000 000 000	= 10 9	(e+9)
mega	M	1 000 000	= 10 6	(e+6)
kilo	k	1 000	= 10 3	(e+3)
hecto	h	100	= 10 2	(e+2)
deca	da	10	= 10 1	(e+1)
------------------	------------	1 --------------------------------------------------------------	---------------	----------
deci	d	0.1	= 10 -1	(e-1)
centi	c	0.01	= 10 -2	(e-2)
milli	m	0.001	= 10 -3	(e-3)
micro	µ	0.000 001	= 10 -6	(e-6)
nano	n	0.000 000 001	= 10 -9	(e-9)
pico	p	0.000 000 000 001	= 10 -12	(e-12)
femto	f	0.000 000 000 000 001	= 10 -15	(e-15)
atto	a	0.000 000 000 000 000 001	= 10 -18	(e-18)
zepto	z	0.000 000 000 000 000 000 001	= 10 -21	(e-21)
yocto	y	0.000 000 000 000 000 000 000 001	= 10 -24	(e-24)

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Table 11. Prefixes for SI Units and Derived SI Units.

The table lists the prefixes used to denote decimal fractions and multiples of SI units and derived SI units. The factos are 10³ⁿ except around unity where additional prefixes are permitted to denote 10^-2 10^-1 10⁰ 10¹ 10². Compound prefixes are not permitted (e.g. millimicro). The prefix attaches directly to the name of a unit, and a prefix symbol attaches directly to the symbol for a unit.

Prefixes and the kilogram

For historical reasons, the name "kilogram" for the SI base unit of mass contains the name "kilo," the SI prefix for 10³. Thus, because compound prefixes are unacceptable, symbols for decimal multiples and submultiples of the unit of mass are formed by attaching SI prefix symbols to g, the unit symbol for gram, and the names of such multiples and submultiples are formed by attaching SI prefixes to the name "gram."
Example: 10^-3 kg = 1 g (1 gram) but not: 10^-3 kg = 1 mkg (1 millikilogram)