Metric and Binary Prefixes
Official SI decimal prefixes and IEC binary prefixes used to express multiples and submultiples of measurement units.
SI / Metric Decimal Prefixes
Defined by the International System of Units (BIPM). Each prefix represents a power of ten.
| Name | Symbol | Exponent | Factor |
|---|---|---|---|
| quecto | q | 10-30 | 1E-30 |
| ronto | r | 10-27 | 1E-27 |
| yocto | y | 10-24 | 1E-24 |
| zepto | z | 10-21 | 1E-21 |
| atto | a | 10-18 | 1E-18 |
| femto | f | 10-15 | 1E-15 |
| pico | p | 10-12 | 1E-12 |
| nano | n | 10-9 | 1E-09 |
| micro | μ | 10-6 | 1E-06 |
| milli | m | 10-3 | 0.001 |
| centi | c | 10-2 | 0.01 |
| deci | d | 10-1 | 0.1 |
| deca | da | 101 | 10 |
| hecto | h | 102 | 100 |
| kilo | k | 103 | 1000 |
| mega | M | 106 | 1E+06 |
| giga | G | 109 | 1E+09 |
| tera | T | 1012 | 1E+12 |
| peta | P | 1015 | 1E+15 |
| exa | E | 1018 | 1E+18 |
| zetta | Z | 1021 | 1E+21 |
| yotta | Y | 1024 | 1E+24 |
| ronna | R | 1027 | 1E+27 |
| quetta | Q | 1030 | 1E+30 |
Source: BIPM — Bureau International des Poids et Mesures
Binary Prefixes
Defined by the International Electrotechnical Commission (IEC 80000-13). Each prefix represents a power of 2¹⁰ = 1024. These are used to remove ambiguity in data-storage contexts.
| Name | Symbol | Exponent | Factor |
|---|---|---|---|
| kibi | Ki | 210 | 1024 |
| mebi | Mi | 220 | 1.049E+06 |
| gibi | Gi | 230 | 1.074E+09 |
| tebi | Ti | 240 | 1.1E+12 |
| pebi | Pi | 250 | 1.126E+15 |
| exbi | Ei | 260 | 1.153E+18 |
| zebi | Zi | 270 | 1.181E+21 |
| yobi | Yi | 280 | 1.209E+24 |
Source: IEC — International Electrotechnical Commission (IEC 80000-13)
Decimal vs. Binary: SI decimal prefixes scale by powers of 10 (kilo = 1,000). IEC binary prefixes scale by powers of 2¹⁰ (kibi = 1,024). Using the correct prefix avoids ambiguity — especially in data storage where both systems are in common use.