Exa-

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

Exa- (symbol E) is a prefix in the metric system denoting 10¹⁸ or 1000000000000000000.

Adopted in 1975, it comes from the Greek ἕξ, used as a prefix ἑξά-, meaning six (like hexa-), because it is equal to 1000⁶.

Examples:

• Multiplying the 10240 megabytes of storage each Gmail user has (as of April 2012) with the estimated 260 million Gmail users, the total storage needed for Gmail is more than an exabyte (not considering backups and how Google might compress the stored data).
• 1 EeV = 10¹⁸ electronvolts = 0.1602 joule
• 1 exasecond is approximately 32 billion years
• 1 exametre is approximately 110 light years
• 0.43 Es ≈ the approximate age of the Universe
• 1.6 Em — 172 ± 12.5 light years — Diameter of Omega Centauri (one of the largest known globular clusters, perhaps containing over a million stars)

Metric prefixes

Prefix Symbol 1000m 10n Decimal Short scale Long scale Since 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 1960 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 1960 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

See also

• 1 exametre
• Binary prefix
• Exabyte
• Exasecond
• Orders of magnitude (numbers)
• SI prefix

References

• International Bureau of Weights and Measures (2006), The International System of Units (SI) (8th ed.), ISBN 92-822-2213-6, http://www.bipm.org/utils/common/pdf/si_brochure_8_en.pdf

External links

• BIPM website
• Exa Corporation
• Exa Proxy Test