Bridget from North Dakota contacted me on April 23, 2006, asking why I do not include the prefixes deca, deci and centi in my conversion tools. Finally I decided to add the following chart to the site; I found it elsewhere on the Internet a couple of years ago and simply cleaned up the page code.
The most commonly used prefixes are in the middle portion of the table. On most browsers these will appear in black-and-white, and the others will appear in maroon against a green background.
| Multiplier | |||
|---|---|---|---|
| Prefix | Symbol | Numerical | Exponential |
| yotta | Y | 1,000,000,000,000,000,000,000,000 | 1024 |
| zetta | Z | 1,000,000,000,000,000,000,000 | 1021 |
| exa | E | 1,000,000,000,000,000,000 | 1018 |
| peta | P | 1,000,000,000,000,000 | 1015 |
| tera | T | 1,000,000,000,000 | 1012 |
| giga | G | 1,000,000,000 | 109 |
| mega | M | 1,000,000 | 106 |
| kilo | k | 1,000 | 103 |
| hecto | h | 100 | 102 |
| deka | da | 10 | 101 |
| no prefix | 1 | 100 | |
| deci | d | 0.1 | 10-1 |
| centi | c | 0.01 | 10-2 |
| milli | m | 0.001 | 10-3 |
| micro | µ | 0.000001 | 10-6 |
| nano | n | 0.000000001 | 10-9 |
| pico | p | 0.000000000001 | 10-12 |
| femto | f | 0.000000000000001 | 10-15 |
| atto | a | 0.000000000000000001 | 10-18 |
| zepto | z | 0.000000000000000000001 | 10-21 |
| yocto | y | 0.000000000000000000000001 | 10-24 |
A Few Notes
- Deka is also commonly spelled deca. Either is correct depending upon your source, but deka is less easily confused with deci.
- In scientific usage the preferred units are multiples or divisions of 1000, which excludes hecto, deka, deci and centi. But these are in widespread use among the general public, and they are considered acceptable for most purposes.
More on Metric Prefixes
- Large and Small Numbers — Metric Prefixes — includes a discussion on how the prefixes are used
- Units: Metric Prefixes [University of North Carolina] — includes a listing of binary prefixes
- Wikipedia article on SI prefixes