Mega

Mega (symbol M) is a SI prefix in the SI system of units denoting a factor of 10⁶, ie one million; 1,000,000.

For example, a megawatt is 1,000,000 watts.

The prefix is sometimes applied in non-standard ways:

• one megaton (a unit often used in measuring the power of nuclear weapons) is 1,000,000 tons. The metric tonne is 1,000 kg, so it is in fact this unit that should be called the megagram.
• in computing, a megabyte is 1,048,576 (2²⁰) bytes. The prefix mebi has been suggested as an alternative.