Kilo-

For other uses, see Kilo (disambiguation).

Kilo- (symbol: k, lowercase) is a unit prefix in the metric system denoting multiplication of the unit by one thousand.

For example:

• one kilogram is 1000 grams
• one kilometre is 1000 metres
• one kilojoule is 1000 joules
• one kilobaud is a rate of transfer used primarily in telecommunications
• one kilobyte is formally equal to 1000 bytes. However, a second definition and usage has historically been in practice in many fields of computer science and information technology, which defines the prefix kilo when used with byte or bit units of information as 1024 (2¹⁰); this is due to the mathematical coincidence that $2^{10} \approx 10^3.$ Thus, in these fields 1 kilobyte is equal to 1 kibibyte, a new unit standardized as part of the binary prefixes to resolve the ambiguity.

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

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

SI prefixes

Prefix	Symbol	1000m	10n	Decimal	Short scale	Long scale	Scientific notation	Since
yotta	Y	10008	1024	1000000000000000000000000	Septillion	Quadrillion	1E24	1991
zetta	Z	10007	1021	1000000000000000000000	Sextillion	Trilliard	1E21	1991
exa	E	10006	1018	1000000000000000000	Quintillion	Trillion	1E18	1975
peta	P	10005	1015	1000000000000000	Quadrillion	Billiard	1E15	1975
tera	T	10004	1012	1000000000000	Trillion	Billion	1E12	1960
giga	G	10003	109	1000000000	Billion	Milliard	1E9	1960
mega	M	10002	106	1000000	Million		1E6	1960
kilo	k	10001	103	1000	Thousand		1E3	1795
hecto	h	10002/3	102	100	Hundred		1E2	1795
deca	da	10001/3	101	10	Ten		1E1	1795
		10000	100	1	One		–	–
deci	d	1000−1/3	10−1	0.1	Tenth		1E-1	1795
centi	c	1000−2/3	10−2	0.01	Hundredth		1E-2	1795
milli	m	1000−1	10−3	0.001	Thousandth		1E-3	1795
micro	μ	1000−2	10−6	0.000001	Millionth		1E-6	1960
nano	n	1000−3	10−9	0.000000001	Billionth	Milliardth	1E-9	1960
pico	p	1000−4	10−12	0.000000000001	Trillionth	Billionth	1E-12	1960
femto	f	1000−5	10−15	0.000000000000001	Quadrillionth	Billiardth	1E-15	1964
atto	a	1000−6	10−18	0.000000000000000001	Quintillionth	Trillionth	1E-18	1964
zepto	z	1000−7	10−21	0.000000000000000000001	Sextillionth	Trilliardth	1E-21	1991
yocto	y	1000−8	10−24	0.000000000000000000000001	Septillionth	Quadrillionth	1E-24	1991