Kilo-

For other uses, see Kilo (disambiguation).

kilo is a unit prefix in the metric system denoting multiplication by one thousand. It has been used in the International System of Units where it has the unit symbol k, in lower case.

The prefix kilo is derived from the Greek word χίλιοι (chilioi), meaning "thousand". It was originally adopted by Antoine Lavoisier's research group in 1795, and introduced into the metric system in France with its establishment in 1799.

Examples:

• one kilogram is 1000 grams
• one kilometer is 1000 metres
• one kilojoule is 1000 joules
• one kilobaud is 1000 bauds
• one kilobit is 1000 bits
• one kilobyte is 1000 bytes.

A second definition has been in common use in some fields of computer science and information technology, which is, however, inconsistent with the SI. It uses kilo as meaning 2¹⁰ = 1024, because of the mathematical coincidence that 2¹⁰ is approximately 10^{3</�sup>. The NIST comments on this confusion: "Faced with this reality, the IEEE Standards Board decided that IEEE standards will use the conventional, internationally adopted, definitions of the SI prefixes."}

• one kilohertz is 1000 hertz

Exponentiation

When units occur in exponentiation, such as in square and cubic forms, any multiplier prefix is considered part of the unit, and thus included in the exponentiation.

• 1 km² means one square kilometre or the area of a square of 1000 m by 1000 m or 10⁶ m².
• 1 km³ means one cubic kilometre or the volume of a cube of 1000 m by 1000 m by 1000 m or 10⁹ m³.

See also

• International System of Units

References

Metric prefixes

Prefix Symbol 1000m 10n Decimal English word Since yotta Y  10008  1024 1000000000000000000000000 septillion 1991 zetta Z  10007  1021 1000000000000000000000 sextillion 1991 exa E  10006  1018 1000000000000000000 quintillion 1975 peta P  10005  1015 1000000000000000 quadrillion 1975 tera T  10004  1012 1000000000000 trillion 1960 giga G  10003  109 1000000000 billion 1960 mega M  10002  106 1000000 million 1960 kilo k  10001  103 1000 thousand 1795 hecto h  10002/3  102 100 hundred 1795 deca da  10001/3  101 10 ten 1795  10000  100 1 one – deci d  1000−1/3  10−1 0.1 tenth 1795 centi c  1000−2/3   10−2 0.01 hundredth 1795 milli m  1000−1  10−3 0.001 thousandth 1795 micro µ  1000−2  10−6 0.000001 millionth 1960 nano n  1000−3  10−9 0.000000001 billionth 1960 pico p  1000−4  10−12 0.000000000001 trillionth 1960 femto f  1000−5  10−15 0.000000000000001 quadrillionth 1964 atto a  1000−6  10−18 0.000000000000000001 quintillionth 1964 zepto z  1000−7  10−21 0.000000000000000000001 sextillionth 1991 yocto y  1000−8  10−24  0.000000000000000000000001 septillionth 1991