Last updated

Mega is a unit prefix in metric systems of units denoting a factor of one million (106 or 1000000). It has the unit symbol M. It was confirmed for use in the International System of Units (SI) in 1960. Mega comes from Ancient Greek : μέγας, romanized: mégas, lit.  'great'. [1]


Common examples of usage


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


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

SI prefixes
PrefixBase 10 Decimal English wordAdoption [nb 1]
NameSymbol Short scale Long scale
yotta Y  1024 1000000000000000000000000 septillion quadrillion1991
zetta Z  1021 1000000000000000000000 sextillion trilliard1991
exa E  1018 1000000000000000000 quintillion trillion1975
peta P  1015 1000000000000000 quadrillion billiard1975
tera T  1012 1000000000000 trillion billion1960
giga G  109 1000000000 billion milliard1960
mega M  106 1000000 million1873
kilo k  103 1000 thousand1795
hecto h  102 100 hundred1795
deca da  101 10 ten1795
  100 1 one
deci d  10−1 0.1 tenth1795
centi c  10−2 0.01 hundredth1795
milli m  10−3 0.001 thousandth1795
micro μ  10−6 0.000001 millionth1873
nano n  10−9 0.000000001 billionth milliardth1960
pico p  10−12 0.000000000001 trillionth billionth1960
femto f  10−15 0.000000000000001 quadrillionth billiardth1964
atto a  10−18 0.000000000000000001 quintillionth trillionth1964
zepto z  10−21 0.000000000000000000001 sextillionth trilliardth1991
yocto y  10−24  0.000000000000000000000001 septillionth quadrillionth1991
  1. Prefixes adopted before 1960 already existed before SI. The introduction of the CGS system was in 1873.

See also

Related Research Articles

A binary prefix is a unit prefix for multiples of units in data processing, data transmission, and digital information, notably the bit and the byte, to indicate multiplication by a power of 2.

The British thermal unit is a unit of heat; it is defined as the amount of heat required to raise the temperature of one pound of water by one degree Fahrenheit. It is also part of the United States customary units. Its counterpart in the metric system is the calorie, which is defined as the amount of heat required to raise the temperature of one gram of water by one degree Celsius. Heat is now known to be equivalent to energy, for which the SI unit is the joule; one BTU is about 1055 joules. While units of heat are often supplanted by energy units in scientific work, they are still used in some fields. For example, in the United States the price of natural gas is quoted in dollars per million BTUs.

The gigabyte is a multiple of the unit byte for digital information. The prefix giga means 109 in the International System of Units (SI). Therefore, one gigabyte is one billion bytes. The unit symbol for the gigabyte is GB.

The kilobyte is a multiple of the unit byte for digital information.

Kilo is a decimal unit prefix in the metric system denoting multiplication by one thousand (103). It is used in the International System of Units, where it has the symbol k, in lower case.

The megabyte is a multiple of the unit byte for digital information. Its recommended unit symbol is MB. The unit prefix mega is a multiplier of 1000000 (106) in the International System of Units (SI). Therefore, one megabyte is one million bytes of information. This definition has been incorporated into the International System of Quantities.

A metric prefix is a unit prefix that precedes a basic unit of measure to indicate a multiple or submultiple of the unit. All metric prefixes used today are decadic. Each prefix has a unique symbol that is prepended to any unit symbol. The prefix kilo-, for example, may be added to gram to indicate multiplication by one thousand: one kilogram is equal to one thousand grams. The prefix milli-, likewise, may be added to metre to indicate division by one thousand; one millimetre is equal to one thousandth of a metre.

Tonne Metric unit of mass equivalent to 1,000 kilograms

The tonne is a metric unit of mass equal to 1,000 kilograms. It is commonly referred to as a metric ton in the United States. It is equivalent to approximately 2,204.6 pounds, 1.102 short tons (US) or approximately 0.984 long tons (UK). The official SI unit is the megagram, a less common way to express the same mass.

The mebibyte is a multiple of the unit byte for digital information. The binary prefix mebi means 220; therefore one mebibyte is equal to 1048576bytes, i.e., 1024 kibibytes. The unit symbol for the mebibyte is MiB.

Square metre SI-derived unit of area

The square metre or square meter is the SI derived unit of area with symbol m2.

The megabit is a multiple of the unit

  1. [[]] bit for digital information. The prefix mega (symbol M) is defined in the International System of Units (SI) as a multiplier of 106 (1 million), and therefore
1,000,000 Natural number

1,000,000, or one thousand thousand, is the natural number following 999,999 and preceding 1,000,001. The word is derived from the early Italian millione, from mille, "thousand", plus the augmentative suffix -one. It is commonly abbreviated as m or M and MM, mm, or mn in financial contexts.

A unit prefix is a specifier or mnemonic that is prepended to units of measurement to indicate multiples or fractions of the units. Units of various sizes are commonly formed by the use of such prefixes. The prefixes of the metric system, such as kilo and milli, represent multiplication by powers of ten. In information technology it is common to use binary prefixes, which are based on powers of two. Historically, many prefixes have been used or proposed by various sources, but only a narrow set has been recognised by standards organisations.

IEEE 1541-2002 is a standard issued in 2002 by the Institute of Electrical and Electronics Engineers (IEEE) concerning the use of prefixes for binary multiples of units of measurement related to digital electronics and computing.

Metric units are units based on the metre, gram or second and decimal multiples or sub-multiples of these. The most widely used examples are the units of the International System of Units (SI). By extension they include units of electromagnetism from the CGS and SI units systems, and other units for which use of SI prefixes has become the norm. Other unit systems using metric units include:

This timeline of binary prefixes lists events in the history of the evolution, development, and use of units of measure for information, the bit and the byte, which are germane to the definition of the binary prefixes by the International Electrotechnical Commission (IEC) in 1998.

In computing and telecommunications, a unit of information is the capacity of some standard data storage system or communication channel, used to measure the capacities of other systems and channels. In information theory, units of information are also used to measure the entropy of random variables and information contained in messages.

The watt is a unit of power. In the International System of Units (SI) it is defined as a derived unit of 1 joule per second, and is used to quantify the rate of energy transfer. In SI base units, the watt is described as kg⋅m2⋅s−3. The watt is named after James Watt, an 18th-century Scottish inventor.

Cubic metre SI unit of volume

The cubic metre or cubic meter is the SI derived unit of volume. Its SI symbol is m3. It is the volume of a cube with edges one metre in length. An alternative name, which allowed a different usage with metric prefixes, was the stère, still sometimes used for dry measure. Another alternative name, no longer widely used, was the kilolitre.


  1. "Oxford English Dictionary (OED Online)" . (3rd ed.). Oxford University Press. June 2001. Retrieved 2017-09-18. Origin: A borrowing from Greek. Etymon: Greek μεγα-. ... Forming scientific and technical terms with the sense ‘very large’, ‘comparatively large’, or (esp. in Pathol.) ‘abnormally large’, often having correlatives beginning micro-, and sometimes also synonyms beginning macro-.