Standard SI Prefixes

Note: The standard SI prefixes are always given with the exponent as a multiple of three. However the prefix names ‘centi’, ‘deci’, ‘deca’ and ‘hecto’ are in common use, and so also shown below. The table below shows these non-standard prefixes in grey to differentiate them from the standard prefixes. Wherever possible, you should use the standard prefixes.

SI prefix	Symbol	Value (Engineering)	Value (Decimal)
quetta	Q	\(10^{30}\)	1 000 000 000 000 000 000 000 000 000 000
ronna	R	\(10^{27}\)	1 000 000 000 000 000 000 000 000 000
yotta	Y	\(10^{24}\)	1 000 000 000 000 000 000 000 000
zetta	Z	\(10^{21}\)	1 000 000 000 000 000 000 000
exa	E	\(10^{18}\)	1 000 000 000 000 000 000
peta	P	\(10^{15}\)	1 000 000 000 000 000
tera	T	\(10^{12}\)	1 000 000 000 000
giga	G	\(10^{9}\)	1 000 000 000
mega	M	\(10^{6}\)	1 000 000
kilo	k	\(10^{3}\)	1 000
hecto	h	\(10^{2}\)	10
deca	da	\(10^{1}\)	10
		\(\mathbf{10^{0}}\)	1
deci	d	\(10^{-1}\)	0.1
centi	c	\(10^{-2}\)	0.01
milli	m	\(10^{-3}\)	0.001
micro	µ	\(10^{-6}\)	0.000 001
nano	n	\(10^{-9}\)	0.000 000 001
pico	p	\(10^{-12}\)	0.000 000 000 001
femto	f	\(10^{-15}\)	0.000 000 000 000 001
atto	a	\(10^{-18}\)	0.000 000 000 000 000 001
zepto	z	\(10^{-21}\)	0.000 000 000 000 000 000 001
yocto	y	\(10^{-24}\)	0.000 000 000 000 000 000 000 001
ronto	r	\(10^{-27}\)	0.000 000 000 000 000 000 000 000 001
quecto	q	\(10^{-30}\)	0.000 000 000 000 000 000 000 000 000 001

SI Brochure: The International System of Units (SI) (2019). Bureau International des Poids et Mesures. Ninth Edition. Table 7 (SI Prefixes). pg. 143.