Metric Prefixes

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A metric prefix precedes a unit of measurement and indicates a multiple or fraction of that unit. For example, kilo may be added to metre to indicate 1000 metres, i.e. there are 1000 metres in a kilometre (km). Likewise, milli may be added may be added to metre to form the word millimetre, i.e. one thousandth of a metre (mm). The table below gives the names and symbols of all metric prefixes in common use, together with their multiple or fraction quantity. These are given in the form 10^n, where, for example, 10 3 is written as 10^3, and 10 -3 is written as 10^-3. In addition, the short and long scale names are given. The short scale names are now used in most English speaking countries. Note that there are some exceptions. For example, as a consequence of binary mathematics, when discussing a computer’s memory or storage capacity a kilobyte is 1,024 bytes, i.e. 2^10 bytes. Likewise, most standards bodies now regard a megabyte as being 1,024,000 bytes, i.e. 1000 x 1024 bytes.

Name / Symbol 10^n Short scale Long scale

yotta Y 10^24 septillion quadrillion Decimal = 1000000000000000000000000 zetta Z 10^21 sextillion thousand trillion (trilliard) Decimal = 1000000000000000000000 exa E 10^18 quintillion trillion Decimal = 1000000000000000000 peta P 10^15 quadrillion thousand billion (billiard) Decimal = 1000000000000000 tera T 10^12 trillion billion Decimal = 1000000000000 giga G 10^9 billion thousand million (milliard) Decimal = 1000000000 mega M 10^6 million million Decimal = 1000000 kilo k 10^3 thousand thousand Decimal = 1000 hecto h 10^2 hundred hundred Decimal = 100 deca h 10^1 ten ten Decimal = 10 Un-named 10^0 one one Decimal = 1 deci d 10^-1 tenth tenth Decimal = 0.1 centi c 10^-2 hundredth hundredth Decimal = 0.01 milli m 10^-3 thousandth thousandth Decimal = 0.001 micro μ 10^-6 millionth millionth Decimal = 0.000001 nano n 10^-9 billionth thousand millionth Decimal = 0.000000001 pico p 10^-12 trillionth billionth Decimal = 0.000000000001 femto f 10^-15 quadrillionth thousand billionth Decimal = 0.000000000000001 atto a 10^-18 quintillionth trillionth Decimal = 0.000000000000000001 zepto z 10^-21 sextillionth thousand trillionth Decimal = 0.000000000000000000001 yocto y 10^-24 septillionth quadrillionth Decimal = 0.000000000000000000000001