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International System of Units (SI) Prefixes
The International System of Units (SI) prefixes are conveniently used to express fractions or multiples of any given unit, and are particularly useful when working with very large or very small numbers. For example, 100 kilometers (km) can be used instead of 100,000 meters (m). As another example, it is more convenient to state that the diameter of a typical mammalian cell is approximately 10 μm rather than 0.00001 m (or 10 × 10-6 m). The table below provides a complete list of the accepted SI prefixes.
Table of International System of Units (SI) prefixes for reporting multiples and fractions
Prefix Symbol 10n Factor Decimal Factor
Yocto y 10-24 0.000 000 000 000 000 000 000 001
Zepto z 10-21 0.000 000 000 000 000 000 001
Atto a 10-18 0.000 000 000 000 000 001
Femto f 10-15 0.000 000 000 000 001
Pico p 10-12 0.000 000 000 001
Nano n 10-9 0.000 000 001
Micro μ 10-6 0.000 001
Milli m 10-3 0.001
Centi c 10-2 0.01
Deci d 10-1 0.1
    100 1
Deka da 101 10
Hecto h 102 100
Kilo k 103 1000
Mega M 106 1000 000
Giga G 109 1000 000 000
Tera T 1012 1000 000 000 000
Peta P 1015 1000 000 000 000 000
Exa E 1018 1000 000 000 000 000 000
Zetta Z 1021 1000 000 000 000 000 000 000
Yotta Y 1024 1000 000 000 000 000 000 000 000






Posted: Monday, May 2, 2005
Last updated: Monday, May 16, 2011