Multiples and submultiples of every unit of measurement
Type the first letter of the name (k for kilometre) or the symbol (km), then pick from the list.
| Unit | Symbol | Value |
|---|
This converter goes from a unit to any of its multiples or submultiples: how many metres in 3.5 km?, how many grams in 250 mg?, how many GB in 1,500 MB? It covers every unit of the International System (metre, gram, second, ampere, kelvin, mole, candela and their derived units: watt, joule, volt, pascal, hertz, newton, ohm…), as well as common units that take prefixes: litre, tonne, are (hectare), bar, watt-hour, ampere-hour, electronvolt, calorie, byte and bit.
Each prefix multiplies the unit by a power of 10. The last four (ronna, quetta, ronto, quecto) were adopted in 2022.
| Prefix | Symbol | Factor | Prefix | Symbol | Factor |
|---|---|---|---|---|---|
| quetta | Q | 10³⁰ | deci | d | 10⁻¹ |
| ronna | R | 10²⁷ | centi | c | 10⁻² |
| yotta | Y | 10²⁴ | milli | m | 10⁻³ |
| zetta | Z | 10²¹ | micro | µ | 10⁻⁶ |
| exa | E | 10¹⁸ | nano | n | 10⁻⁹ |
| peta | P | 10¹⁵ | pico | p | 10⁻¹² |
| tera | T | 10¹² | femto | f | 10⁻¹⁵ |
| giga | G | 10⁹ | atto | a | 10⁻¹⁸ |
| mega | M | 10⁶ | zepto | z | 10⁻²¹ |
| kilo | k | 10³ | yocto | y | 10⁻²⁴ |
| hecto | h | 10² | ronto | r | 10⁻²⁷ |
| deca (deka) | da | 10¹ | quecto | q | 10⁻³⁰ |
To go from one prefix to another, multiply by 10 raised to the difference between the exponents:
Wanted value = value × 10^(original exponent − wanted exponent)
Example: 3.5 km in m → 3.5 × 10^(3 − 0) = 3,500 m. This simply moves the decimal point, so it is done exactly, with no rounding error, even for extreme values.
Areas and volumes: the prefix is squared or cubed as well. 1 km² = (10³ m)² = 10⁶ m², and 1 cm³ = (10⁻² m)³ = 10⁻⁶ m³ = 1 mL.
Bytes and bits: SI prefixes are powers of 10 (1 kB = 1,000 bytes), while binary prefixes are powers of 2 (1 KiB = 1,024 bytes, 1 GiB = 1,073,741,824 bytes). One byte is 8 bits.
Equivalent units: 1 L = 1 dm³, 1 ha = 1 hm² = 10,000 m², 1 t = 1 Mg = 1,000 kg, 1 bar = 100,000 Pa, 1 Wh = 3,600 J, 1 Ah = 3,600 C, 1 cal = 4.184 J, 1 eV = 1.602176634 × 10⁻¹⁹ J, 1 pc ≈ 3.086 × 10¹⁶ m. For these conversions, the result is given to 15 significant digits.
The kilogram is the SI base unit, but prefixes are applied to the gram: we say milligram, not “microkilogram”. The kilogram therefore appears as “kilo + gram”.
1 MB (megabyte) = 1,000,000 bytes, 1 MiB (mebibyte) = 1,048,576 bytes. Drive makers use MB and GB, while some operating systems show MiB and GiB but call them “MB” and “GB”: that is why a 1 TB drive seems to hold only 931 “GB”.
No: this tool is dedicated to multiples and submultiples, which follow from powers of 10. Imperial units and temperature scales need other formulas.
When usage is limited, only the prefixes actually used are offered: hectare, decare and centiare for the are, kilotonne, megatonne and gigatonne for the tonne, kilocalorie for the calorie, and only multiples for bytes and bits.
No need: type “micro” or the letter u instead (um for µm, ug for µg).
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