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Numerical Prefixes: Mathematical, Digital, IEC

These are the commonly used numerical prefixes in the English language, but most seem to have bases similar to words in European languages; e.g., French, Latin, and Greek. * These prefixes were declared in 2022 by the General Conference on Weights and Measures in Versailles, France.

Prefix Symbol Name Multiplier
vendeko v decillionth 10-33
quecto*   nonillionth 10-30
x octillionth 10-27
yocto y septillionth 10-24
zepto z sextillionth 10-21
atto a quintillionth 10-18
femto f quadrillionth 10-15
pico p trillionth 10-12
nano n billionth 10-9
micro µ millionth 10-6
milli m thousandth 10-3
centi c hundredth 10-2
deci d tenth 10-1
deka da ten 101
hecto h hundred 102
kilo k thousand 103
mega M million 106
giga G billion 109
tera T trillion 1012
peta P quadrillion 1015
exa E quintillion 1018
zetta Z sextillion 1021
yotta Y septillion 1024
X octillion 1027
quetta* V nonillion 1030
vendeka V decillion 1033
    undecillion 1036
    duodecillion 1039
    tredecillion 1042
    quattodecillion 1045
    quindecillion 1048
    sexdecillion 1051
    septendecillion 1054
    octodecillion 1057
    novemdecillion 1060
    vigindecillion 1063
    googol 10100
    googolplex 10google
Digital (Base 2)
Prefix Symbol Multiplier Value
peta P 250 1,125,899,906,842,624
tera T 240 1,099,511,627,776
giga G 230 1,073,741,824
Mega M 220 1,048,576
kilo k 210 1,024


IEC Version
Prefix Symbol Multiplier Value
exbi Ei 260 1,152,921,504,606,846,976
pebi Pi 250 1,125,899,906,842,624
tebi Ti 240 1,099,511,627,776
gibi Gi 230 1,073,741,824
mebi Mi 220 1,048,576
kibi Ki 210 1,024


Non-Technical Writing
Prefix Value
uni,  mono 1
 bi 2
  tri 3
quadr 4
quint, penta 5
  hex, sex 6
hept, sept 7
octo 8
novem 9
deca, deka 10



† 1,000,000,000 is called "one billion" in the U.S., U.K., France (before May 3, 1961), Brazil, Puerto Rico, Greece, and in Italy, Russia and Turkey it is referred to as "one billion" when written out, but as "one milliard" when written as 109. 1,000,000,000,000 is called "one trillion" in the U.S., but is called "one billion" in Germany, the Netherlands, Austria, Sweden, Norway, Denmark, Finland, France (after May 3, 1961), Portugal, Poland. It is best to check for current definitions for each country to be certain to get it right, or better yet, just write it out numerically to avoid confusion.

Thanks to Duncan for the zepto info.



Posted April 17, 2004

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