SI Prefixes List

An SI prefix (also known as a metric prefix) is a name or associated symbol that precedes a unit of measure (or its symbol) to form a decimal multiple or submultiple. The abbreviation SI is from the French language name Système International d’Unités (also known as International System of Units). SI prefixes are used to reduce the quantity of zeroes in numerical equivalencies. Twenty SI prefixes are available to combine with units of measure. On this page you can see SI Prefix Chart.

SI Prefixes List
Below, you can find the chart of 24 prefixes introduced and governed by Bureau International des Poids et Mesures (eng. International Bureau of Weights and Measures ) .The abbreviation SI is from the French language name Système International d’Unités (eng: International System of Units )

Prefix Symbol 10n Long/Short Scale
yotta (gr. okto - eight) Y 1024 Quadrillion/Septillion
zetta (lat. septem - seven) Z 1021 Trilliard/Sextillion
exa (gr. ex - six) E 1018 Trillion/Quintillion
peta (gr. penta - five) P 1015 Billiard/Quadrillion
tera (gr. teras – monster) T 1012 Billion/Trillion
giga (gr. gigas – giant) G 109 Milliard/Billion
mega (gr. megas – great) M 106 Million/Million
kilo (gr. khilioi – thousand) k 10³ Thousand/Thousand
hecto (gr. hekaton – hundred) h 10² Hundred/Hundred
deca (gr. deka – ten) da 101 Ten/Ten
100 One/One
decy (lat. decimus – tenth) d 10-1 Tenth/Tenth
centy (lac. centum – hundredth) c 10-2 Hundredth/Hundredth
milli (lac. mille – thousand) m 10-3 Thousandth/Thousandth
mikro (gr. mikros – small) µ 10-6 Millionth/Millionth
nano (gr. nanos – dwarf) n 10-9 Milliardth/Billionth
pico (it. piccolo – small) p 10-12 Billionth/Trillionth
femto (den. femten – fifteen) f 10-15 Billiardth/Quadrillionth
atto (den. atten – eighteen) a 10-18 Trillionth/Quintillionth
zepto (lat. septem - seven) z 10-21 Trilliardth/Sextillionth
yokto (gr. okto - eight) y 10-24 Quadrillionth/Septillionth
Short And Long Scale
In most English-speaking countries short scale is used. In short scale Billion prefix (109) is giga, Trillion prefix (1012) is tera, Billionth prefix (10-9) is nano, Trillionth prefix (10-12 is pico, and so on.

In most European countries long scale is used. In long scale Billion prefix (1012) is tera, Trillion prefix (1018) is exa, Billionth prefix (10-12) is pico, Trillionth prefix (10-18) is atto, and so on.
Prefixes In Computing
Prefixes K,M,G,T,P (kilo,mega,giga,tera,peta) are commonly used in computing, where they are applied to information and storage units. Since informational systems are based on power of 2, this led to following meaning of prefixes in computer science:

PrefixSymbol2nDecimal Value
kiloK2101 024
megaM2201 048 576
gigaG230 1 073 741 824
teraT2401 099 511 627 776
petaP2501 125 899 906 842 624
See also: Data Capacity Converter

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