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

The above SI prefixes can be applied to all SI units, except those associated with computer binary data. For example:

Old Definitions:
• 1 kb = (2¹⁰) bits = 1,024 bits
• 1 MB = (2¹⁰)² Bytes = 1,048,576 Bytes

To make the SI prefixes universal and to avoid confusion in the future, International Electrotechnical Commission (IEC), the leading international organization for worldwide standardization in electrotechnology, approved in December 1998 standard names and symbols of prefixes for binary multiples to be used in the fields of data processing and transmission. The prefixes are:

Name	Prefix	Symbol	Factor
kilobinary	kibi	Ki	210
megabinary	mebi	Mi	(210)2
gigabinary	gibi	Gi	(210)3
terabinary	tebi	Ti	(210)4
petabinary	pebi	Pi	(210)5
exabinary	exbi	Ei	(210)6

Based on the new definitions, the SI prefixes, k, M, and G, are back to their original meaning of 1,000, 1,000,000, and 1,000,000,000, respectively. The commonly known binary prefixes are written as Ki, Mi, and Gi and pronounced as kibi, mebi, and gibi, respectively.

New Definitions: (See the unit conversion calculator for more binary data units.)
• 1 kilo-bit = 1 kb = 10³ bits = 1,000 bits
• 1 kilobinarybit = 1 kibibit = 1 Kib = (2¹⁰) bits = 1,024 bits
• 1 megabyte = 1 MB = 10⁶ Bytes = 1,000,000 Bytes
• 1 megabinarybyte = 1 mebibyte = 1 MiB = (2¹⁰)² Bytes = 1,048,576 Bytes

The IEEE Standards Board decided that IEEE standards will be using the conventional, internationally adopted, definitions of the base-ten SI prefixes, except that the base-two definition may be used if such usage is explicitly pointed out on a case-by-case basis.