SI Prefixes

The SI is a decimal system so there are no fractions and the multiples and submultiples are being formed using a series of prefixes ranging from yotta (\(10^{24}\)) up to yocto (\(10^{-24}\)). The range of prefixes is shown in following table. Each prefix beyond \(10^{\pm 3}\) represents a change in magnitude of \(10^3\).

Multiple			Submultiple
Prefix (Etymology)	Symbol	Multiply by	Prefix (Etymology)	Symbol	Multiply by
yotta	Y	\(10^{24}\)	deci	d	\(10^{-1}\)
zetta	Z	\(10^{21}\)	centi	c	\(10^{-2}\)
exa	E	\(10^{18}\)	milli	m	\(10^{-3}\)
peta	P	\(10^{15}\)	micro	µ	\(10^{-6}\)
tera	T	\(10^{12}\)	nano	n	\(10^{-9}\)
giga	G	\(10^9\)	pico	p	\(10^{-9}\)
mega	M	\(10^{6}\)	femto	f	\(10^{-15}\)
kilo	k	\(10^{3}\)	atto	a	\(10^{-18}\)
hecto	h	\(10^2\)	zepto	z	\(10^{-21}\)
deca	da	\(10\)	yocto	y	\(10^{-24}\)

In computing, a custom arose of using the metric prefixes to specify the powers of 2. For example, a kilobit is usually equal to \(2^{10} = 1024\) bits instead of 1000 bits. This practice still leads to considerable confusion. In 1998 the International Electrotechnical Commission (IEC) approved new prefixes especially dedicated to the powers of 2.