Physics reference
SI prefixes
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A comphrensive table of all SI multiples and submultiples.
SI prefixes.
prefixsymbolvalueexpanded valueEnglish nameadopted
(obsoleted)
quettaQ10301 000 000 000 000 000 000 000 000 000 000U.S. nonillion2022
rontaR10271 000 000 000 000 000 000 000 000 000U.S. octillion2022
yottaY10241 000 000 000 000 000 000 000 000U.S. septillion1991
zettaZ10211 000 000 000 000 000 000 000U.S. sextillion1991
exaE10181 000 000 000 000 000 000U.S. quintillion1975
petaP10151 000 000 000 000 000U.S. quadrillion1975
teraT10121 000 000 000 000U.S. trillion1960
gigaG1091 000 000 000U.S. billion1960
megaM1061 000 000million1960
myria/myriomy [footnote 1] 10410 000ten thousand1795/1889 (1960)
kilok1031 000thousand1795/1889
hectoh102100hundred1795/1889
deca/dekada [footnote 2] 10110ten1795/1889
1001one
decid10-10.1tenth1795/1889
centic10-20.01hundredth1795/1889
millim10-30.001thousandth1795/1889
microμ (u) [footnote 3] 10-60.000 001millionth1960
nanon10-90.000 000 001U.S. billionth1960
picop10-120.000 000 000 001U.S. trillionth1960
femtof10-150.000 000 000 000 001U.S. quadrillionth1964
attoa10-180.000 000 000 000 000 001U.S. quintillionth1964
zeptoz10-210.000 000 000 000 000 000 001U.S. sextillionth1991
yoctoy10-240.000 000 000 000 000 000 000 001U.S. septillionth1991
rontor10-270.000 000 000 000 000 000 000 000 001U.S. octillionth2022
quectoq10-300.000 000 000 000 000 000 000 000 000 001U.S. nonillionth2022
Legend.
prefix
The name of the prefix, which is prepended directly before a unit name with no spaces. For instance, prepending the prefix mega to the SI unit joule gives the word megajoule.
symbol
The symbol of the prefix, to be used in conjunction with the symbol for a unit, following the rules above. For instance, one would write MJ for megajoule.
value, expanded value
The value of the prefix, written in an abbreviated matter and then expanded.
English name
The English name for the unit; if U.S. and U.K. nomenclature differs, then both versions are shown.
adopted (obsoleted)
The year of adoption (with the year of becoming obsoleted in parentheses).
Footnotes.
1.
The myria prefix (also spelled myrio) was originally introduced in the metric system in 1795 and approved in the first General Conference on Weights and Measures (GCPM) in 1889, but was declared obsolete in 1960.

footnote 1
2.
The deca prefix is spelled deka in British English. Spellings may vary, but its official symbol is always da, not dk.

footnote 2
3.
The micro prefix is actually represented by the Greek letter mu, but is often written in ASCII as u.

footnote 3
Cross-references.
Physics reference: Binary prefixes
     A comphrensive table of all binary multiples.
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