Mega- (symbol M) is an SI prefix in the SI system of units denoting a factor of 106, 1,000,000 (one million).
For example, 1 MW (megawatt) = 1,000,000 watts = 1,000 kilowatts.
Confirmed in 1960, it comes from the Greek μέγας, meaning great.
Other common examples of usage
Square and cubic forms
As the SI-prefixes take precedence over exponents,
- 1 Mm2 means one square megametre or the size of a square of 1,000,000 m × 1,000,000 m or m2 (and not 1,000,000 × a square metre or m²)
- 1 Mm3 means one cubic megametre or the size of a cube of 1,000,000 m × 1,000,000 m × 1,000,000 m or m2 (and not 1,000,000 × a cubic metre or m3)
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, but is yet to be widely used.