This article describes the SI prefix. For other meanings, see Kilo.
kilo- (symbol: k) is a prefix in the SI and other systems of units denoting 103 or 1,000. For example:
Officially adopted in 1795 (though in common use before that), it comes from the Greek χίλιοι ("khilioi"), meaning thousand.
SI prefixes
| 1000m |
10n |
Prefix |
Symbol |
Since[1] |
Short scale |
Long scale |
Decimal |
| 10008 |
1024 |
yotta- |
Y |
1991 |
Septillion |
Quadrillion |
1 000 000 000 000 000 000 000 000 |
| 10007 |
1021 |
zetta- |
Z |
1991 |
Sextillion |
Trilliard |
1 000 000 000 000 000 000 000 |
| 10006 |
1018 |
exa- |
E |
1975 |
Quintillion |
Trillion |
1 000 000 000 000 000 000 |
| 10005 |
1015 |
peta- |
P |
1975 |
Quadrillion |
Billiard |
1 000 000 000 000 000 |
| 10004 |
1012 |
tera- |
T |
1960 |
Trillion |
Billion |
1 000 000 000 000 |
| 10003 |
109 |
giga- |
G |
1960 |
Billion |
Milliard |
1 000 000 000 |
| 10002 |
106 |
mega- |
M |
1960 |
Million |
1 000 000 |
| 10001 |
103 |
kilo- |
k |
1795 |
Thousand |
1 000 |
| 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 |
0.000 001 |
| 1000−3 |
10−9 |
nano- |
n |
1960 |
Billionth |
Milliardth |
0.000 000 001 |
| 1000−4 |
10−12 |
pico- |
p |
1960 |
Trillionth |
Billionth |
0.000 000 000 001 |
| 1000−5 |
10−15 |
femto- |
f |
1964 |
Quadrillionth |
Billiardth |
0.000 000 000 000 001 |
| 1000−6 |
10−18 |
atto- |
a |
1964 |
Quintillionth |
Trillionth |
0.000 000 000 000 000 001 |
| 1000−7 |
10−21 |
zepto- |
z |
1991 |
Sextillionth |
Trilliardth |
0.000 000 000 000 000 000 001 |
| 1000−8 |
10−24 |
yocto- |
y |
1991 |
Septillionth |
Quadrillionth |
0.000 000 000 000 000 000 000 001 |
- The metric system was introduced in 1795 with six prefixes. The other dates relate to recognition by a resolution of the CGPM.
- The 1948 recognition of the micron by the CGPM was abrogated in 1967.
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Use in computing
In binary computing, kilo does not always denote 1,000 but is sometimes equal to 1,024 (210), most often when discussing memory and file sizes. See binary prefix for more details.
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