mega (M) (as a prefix to units of semiconductor storage capacity)

A multiplier equal to 1 048 576 (2²⁰ or K², where K = 1024).

NOTE 1 Contrast with the SI prefix mega (M) equal to 10⁶, as in a 1‑Mb/s data transfer rate, which is equal to 1 000 000 bits per second.

NOTE 2 The definitions of kilo, giga, and mega based on powers of two are included only to reflect common usage. IEEE/ASTM SI 10‑1997 states "This practice frequently leads to confusion and is deprecated." Further confusion results from the popular use of a "megabyte" consisting of 1 024 000 bytes to define the capacity of the familiar "1.44‑MB" diskette. An alternative system is found in Amendment 2 to IEC 60027‑2: Letter symbols to be used in electrical technology - Part 2:

Prefixes for binary multipliers
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Factor Name Symbol Origin Derivation
2¹⁰ kibi Ki kilo + binary: (2¹⁰)¹ = 1 024 kilo: (10³)¹
2²⁰ mebi Mi mega + binary: (2¹⁰)² = 1 048 576 mega: (10³)²
2³⁰ gibi Gi giga + binary: (2¹⁰)³ = 1 073 741 824 giga: (10³)³
2⁴⁰ tebi Ti tera + binary: (2¹⁰)⁴ = 1 099 511 627 776 tera: (10³)⁴

IEC suggests that, in English, the first syllable of the name of the binary-multiplier prefix should be pronounced in the same way as the first syllable of the name of the corresponding SI prefix and that the second syllable should be pronounced as "bee".