For other uses, see Kilo (disambiguation).
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Look up kilo- in Wiktionary, the free dictionary. |
Kilo (symbol: k) is a unit prefix in the International System of Units (SI) denoting 103 or 1000. For example:
- one kilogram is 1000 grams
- one kilometre is 1000 metres
- one kilojoule is 1000 joules
- one kilobyte is equal to either 1000 bytes or, according to traditional use in some fields of computer science, 1024 (210) bytes. The latter meaning is most often used when discussing computer memory and storage sizes. This usage has been officially replaced in the standardization bodies by the definition of binary prefixes.
The kilo prefix is derived from the Greek word χίλιοι ("chilioi"), meaning thousand. It was originally adopted by Antoine Lavoisier and his group in 1795, and introduced into the metric system in France with its establishment in 1799. The General Conference on Weights and Measures was formed in 1875.
Exponentiation
When units occur in exponentiation, such as in square and cubic forms, any size prefix is considered part of the unit, and thus included in the exponentiation.
- 1 km2 means one square kilometre or the size of a square of 1,000 m by 1,000 m or 106 m2.
- 1 km3 means one cubic kilometre or the size of a cube of 1,000 m by 1,000 m by 1,000 m or 109 m3.
| 1000m | 10n | Prefix | Symbol | Since[1] | Short scale | Long scale | Decimal |
|---|---|---|---|---|---|---|---|
| 10008 | 1024 | yotta | Y | 1991 | Septillion | Quadrillion | 1000000000000000000000000 |
| 10007 | 1021 | zetta | Z | 1991 | Sextillion | Trilliard | 1000000000000000000000 |
| 10006 | 1018 | exa | E | 1975 | Quintillion | Trillion | 1000000000000000000 |
| 10005 | 1015 | peta | P | 1975 | Quadrillion | Billiard | 1000000000000000 |
| 10004 | 1012 | tera | T | 1960 | Trillion | Billion | 1000000000000 |
| 10003 | 109 | giga | G | 1960 | Billion | Milliard | 1000000000 |
| 10002 | 106 | mega | M | 1960 | Million | 1 000 000 | |
| 10001 | 103 | kilo | k | 1795 | Thousand | 1000 | |
| 10002⁄3 | 102 | hecto | h | 1795 | Hundred | 100 | |
| 10001⁄3 | 101 | deca | da | 1795 | Ten | 10 | |
| 10000 | 100 | (none) | (none) | NA | One | 1 | |
| 1000−1⁄3 | 10−1 | deci | d | 1795 | Tenth | 0.1 | |
| 1000−2⁄3 | 10−2 | centi | c | 1795 | Hundredth | 0.01 | |
| 1000−1 | 10−3 | milli | m | 1795 | Thousandth | 0.001 | |
| 1000−2 | 10−6 | micro | µ | 1960[2] | Millionth | 0.000001 | |
| 1000−3 | 10−9 | nano | n | 1960 | Billionth | Milliardth | 0.000000001 |
| 1000−4 | 10−12 | pico | p | 1960 | Trillionth | Billionth | 0.000000000001 |
| 1000−5 | 10−15 | femto | f | 1964 | Quadrillionth | Billiardth | 0.000000000000001 |
| 1000−6 | 10−18 | atto | a | 1964 | Quintillionth | Trillionth | 0.000000000000000001 |
| 1000−7 | 10−21 | zepto | z | 1991 | Sextillionth | Trilliardth | 0.000000000000000000001 |
| 1000−8 | 10−24 | yocto | y | 1991 | Septillionth | Quadrillionth | 0.000000000000000000000001 |
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