Mega-

For other uses, see Mega (disambiguation).

Mega- (symbol M) is an prefix in the metric system denoting a factor of million (10⁶ or 1000000). Confirmed in 1960, it 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 1,000,000 m by 1,000,000 m or 10¹² m², and not 1,000,000 square metres (10⁶ m²).
• 1 Mm³ means one cubic megametre or the size of a cube of 1,000,000 m by 1,000,000 m by 1,000,000 m or 10¹⁸ m³, and not 1,000,000 cubic metres (10⁶ m³)

Computing

In computing, mega can sometimes denote 1,048,576 (2²⁰) of information units (example: a megabyte, a megaword), but can denote 1,000,000 (10⁶) of other quantities, for example, transfer rates: 1 megabit/s = 1,000,000 bit/s.

The prefix mebi has been suggested as a prefix for 2²⁰ to avoid ambiguity.

SI prefixes

Prefix	Symbol	1000m	10n	Decimal	Short scale	Long scale	Scientific notation	Since
yotta	Y	10008	1024	1000000000000000000000000	Septillion	Quadrillion	1E24	1991
zetta	Z	10007	1021	1000000000000000000000	Sextillion	Trilliard	1E21	1991
exa	E	10006	1018	1000000000000000000	Quintillion	Trillion	1E18	1975
peta	P	10005	1015	1000000000000000	Quadrillion	Billiard	1E15	1975
tera	T	10004	1012	1000000000000	Trillion	Billion	1E12	1960
giga	G	10003	109	1000000000	Billion	Milliard	1E9	1960
mega	M	10002	106	1000000	Million		1E6	1960
kilo	k	10001	103	1000	Thousand		1E3	1795
hecto	h	10002/3	102	100	Hundred		1E2	1795
deca	da	10001/3	101	10	Ten		1E1	1795
		10000	100	1	One		–	–
deci	d	1000−1/3	10−1	0.1	Tenth		1E-1	1795
centi	c	1000−2/3	10−2	0.01	Hundredth		1E-2	1795
milli	m	1000−1	10−3	0.001	Thousandth		1E-3	1795
micro	μ	1000−2	10−6	0.000001	Millionth		1E-6	1960
nano	n	1000−3	10−9	0.000000001	Billionth	Milliardth	1E-9	1960
pico	p	1000−4	10−12	0.000000000001	Trillionth	Billionth	1E-12	1960
femto	f	1000−5	10−15	0.000000000000001	Quadrillionth	Billiardth	1E-15	1964
atto	a	1000−6	10−18	0.000000000000000001	Quintillionth	Trillionth	1E-18	1964
zepto	z	1000−7	10−21	0.000000000000000000001	Sextillionth	Trilliardth	1E-21	1991
yocto	y	1000−8	10−24	0.000000000000000000000001	Septillionth	Quadrillionth	1E-24	1991

See also

• SI prefix
• Binary prefix
• Mebibyte
• Orders of magnitude

External links

• BIPM website