Pico-

This article is about the SI prefix. For other uses, see Pico (disambiguation).

Pico- (symbol p) is a unit prefix in the metric system denoting one trillionth, a factor of 10⁻¹² (0.000000000001).

Derived from the Spanish pico, meaning peak, beak, bit, this was one of the original 12 prefixes defined in 1960 when the International System of Units was established.

The radius of atoms range from 25 picometers (hydrogen) to 260 picometers (caesium). One picolight-year is about nine kilometers (six miles).

SI prefixes

Prefix Base 1000 Base 10 Decimal English word Adoption Name Symbol Short scale Long scale yotta Y  10008  1024 1000000000000000000000000  septillion  quadrillion 1991 zetta Z  10007  1021 1000000000000000000000  sextillion  trilliard 1991 exa E  10006  1018 1000000000000000000  quintillion  trillion 1975 peta P  10005  1015 1000000000000000  quadrillion  billiard 1975 tera T  10004  1012 1000000000000  trillion  billion 1960 giga G  10003  109 1000000000  billion  milliard 1960 mega M  10002  106 1000000  million 1873 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 1873 nano n  1000−3  10−9 0.000000001  billionth  milliardth 1960 pico p  1000−4  10−12 0.000000000001  trillionth  billionth 1960 femto f  1000−5  10−15 0.000000000000001  quadrillionth  billiardth 1964 atto a  1000−6  10−18 0.000000000000000001  quintillionth  trillionth 1964 zepto z  1000−7  10−21 0.000000000000000000001  sextillionth  trilliardth 1991 yocto y  1000−8  10−24  0.000000000000000000000001  septillionth  quadrillionth 1991