Mega-

For other uses, see Mega (disambiguation).

Mega is a unit prefix in the metric system denoting a factor of one million (10⁶ or 1000000). It was confirmed for use in the International System of Units (SI) in 1960. Mega comes from the Greek μέγας, meaning great.

Other common examples of usage

• megapixel - 1 million pixels in a digital camera
• one megatonne (of TNT) (a unit often used in measuring the explosive power of nuclear weapons) is the approximate energy released on igniting one million tonnes of TNT.
• megahertz — frequency of electromagnetic radiation for radio and television broadcasting, GSM, etc. 1 MHz = 1,000,000 Hz.

Exponentiation

When units occur in exponentiation, such as in square and cubic forms, any size prefix is considered part of the unit, and thus included in the exponentiation.

• 1 Mm² means one square megametre or the size of a square of 1000000m by 1000000m or 10¹²m², and not 1000000square metres (10⁶ m²).
• 1 Mm³ means one cubic megametre or the size of a cube of 1000000m by 1000000m by 1000000m or 10¹⁸ m³, and not 1000000cubic metres (10⁶ m³)

Computing

In computing, mega may sometimes denote 1,048,576 (2²⁰) of information units (example: a megabyte, a megaword), but denotes 1000000 (10⁶) units of other quantities, for example, transfer rates: 1megabit/s = 1000000bit/s. The prefix mebi has been suggested as a prefix for 2²⁰ to avoid ambiguity.

Metric prefixes

Prefix Symbol 1000m 10n Decimal English word Since yotta Y  10008  1024 1000000000000000000000000 septillion 1991 zetta Z  10007  1021 1000000000000000000000 sextillion 1991 exa E  10006  1018 1000000000000000000 quintillion 1975 peta P  10005  1015 1000000000000000 quadrillion 1975 tera T  10004  1012 1000000000000 trillion 1960 giga G  10003  109 1000000000 billion 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 1960 pico p  1000−4  10−12 0.000000000001 trillionth 1960 femto f  1000−5  10−15 0.000000000000001 quadrillionth 1964 atto a  1000−6  10−18 0.000000000000000001 quintillionth 1964 zepto z  1000−7  10−21 0.000000000000000000001 sextillionth 1991 yocto y  1000−8  10−24  0.000000000000000000000001 septillionth 1991

See also

• Metric prefix
• Binary prefix
• Mebibyte
• Order of magnitude

External links

• BIPM website