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Mega- (Prefix) — Definition, Formula & Examples

Mega- is a metric prefix meaning one million, or 1,000,000. You see it in everyday units like megabytes (MB) and megawatts (MW).

The prefix mega-, abbreviated M, denotes a factor of 10610^6 (one million) in the International System of Units (SI). Attaching it to a base unit multiplies that unit by 1,000,000.

Key Formula

1  mega-unit=106  base units1\;\text{mega-unit} = 10^6\;\text{base units}
Where:
  • 10610^6 = The multiplication factor, equal to 1,000,000

How It Works

To convert from a mega-unit to the base unit, multiply by 10610^6. To convert from the base unit to a mega-unit, divide by 10610^6. For example, 5 megahertz equals 5×1065 \times 10^6 hertz. The abbreviation is always a capital M placed before the unit symbol, such as MHz, MW, or Mg.

Worked Example

Problem: A power plant produces 3 megawatts (MW) of electricity. How many watts is that?
Apply the prefix: Mega- means multiply by one million, so replace the prefix with the factor.
3  MW=3×106  W3\;\text{MW} = 3 \times 10^6\;\text{W}
Compute: Multiply 3 by 1,000,000.
3×1,000,000=3,000,000  W3 \times 1{,}000{,}000 = 3{,}000{,}000\;\text{W}
Answer: 3 MW equals 3,000,000 watts.

Why It Matters

Mega- appears constantly in science and technology — megabytes describe file sizes, megahertz describe processor speeds, and megapascals describe material strength. Recognizing metric prefixes lets you quickly interpret and compare measurements without writing out long strings of zeros.

Common Mistakes

Mistake: Confusing the mega- abbreviation (capital M) with the milli- abbreviation (lowercase m).
Correction: Capital M always stands for mega- (10610^6), while lowercase m stands for milli- (10−310^{-3}). The difference is a factor of one billion, so mixing them up causes enormous errors.