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SI Prefixes Table

Example: 1 TW=1000 GW (W=Watt)

Symbol Prefix Factor
Y Yotta 1024
Z Zetta 1021
E Exa 1018
P peta 1015
T tera 1012
G giga 109
M Mega 106
k kilo 103
h hecto 102
da deca 101
d deci 10-1
c centi 10-2
m milli 10-3
µ u micro 10-6
n nano 10-9
p pico 10-12
f femto 10-15
a atto 10-18
z zepto 10-21
y yokto 10-24

Note: In the computer world things are a bit different:

Symbol Prefix Factor Factor
P peta 250 1125899906842624
T tera 240 1099511627776
G giga 230 1073741824
M Mega 220 1048576
k kilo 210 1024

There is also the prefixes adopted by IEC in order to cope with the digital world. These are not widely used (yet).

Symbol Prefix Factor Factor
Ei exbi 260 1152921504606846976
Pi pebi 250 1125899906842624
Ti tebi 240 1099511627776
Gi gibi 230 1073741824
Mi mebi 220 1048576
Ki kibi 210 1024
Contributor: Joakim Ögren, Haudy Kazemi, Knut Kristan Weber Daniel Nilsson
Source: Farnell Components Catalogue

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Document last modified: 2002-01-13