Metric prefix chart
The metric prefixes from tera down to pico, with their symbols and the power of ten each represents. Prefixes attach to any unit to scale it: a kilometre is a thousand metres, a millisecond is a thousandth of a second.
Common metric prefixes
| Prefix | Symbol | Power of ten | Factor |
|---|---|---|---|
| tera | T | 10¹² | 1,000,000,000,000 |
| giga | G | 10⁹ | 1,000,000,000 |
| mega | M | 10⁶ | 1,000,000 |
| kilo | k | 10³ | 1,000 |
| hecto | h | 10² | 100 |
| deca | da | 10¹ | 10 |
| deci | d | 10⁻¹ | 0.1 |
| centi | c | 10⁻² | 0.01 |
| milli | m | 10⁻³ | 0.001 |
| micro | μ | 10⁻⁶ | 0.000001 |
| nano | n | 10⁻⁹ | 0.000000001 |
| pico | p | 10⁻¹² | 0.000000000001 |
Each prefix stands for a power of ten and can be added to any base unit, such as the metre, gram, or second. Kilo means a thousand, milli a thousandth, mega a million, and micro a millionth. The symbols are case-sensitive: a capital M is mega, a lowercase m is milli, a thousand-million-fold difference.
Need powers of ten?
See the Powers of Ten Chart.
How prefixes scale units
A metric prefix multiplies the base unit by its power of ten. So a kilogram is 1,000 grams, a centimetre is one hundredth of a metre, and a microsecond is one millionth of a second. The same set of prefixes works across every metric unit, which is what makes the system so consistent and easy to convert within.
Watch the capitalization
Prefix symbols are case-sensitive and the difference is huge. Capital M means mega (a million) while lowercase m means milli (a thousandth), so Mg and mg differ by a factor of a billion. Capital K is not used; kilo is always a lowercase k. Getting the case right matters, especially in science and engineering.
FAQ
What does the prefix kilo mean?
One thousand. A kilometre is 1,000 metres and a kilogram is 1,000 grams.
What is the difference between milli and micro?
Milli is one thousandth (10 to the negative 3); micro is one millionth (10 to the negative 6), a thousand times smaller.
Why are prefix symbols case-sensitive?
Because the same letter can mean very different scales: capital M is mega (million), lowercase m is milli (thousandth).