Metric Prefix Converter
Convert a value from one SI prefix to another — for example kilometres to micrometres or gigawatts to milliwatts — across all 24 prefixes, including the four added in 2022: ronna, quetta, ronto and quecto. Type a unit symbol or leave it blank, enter ordinary or scientific notation, and get an exact result with the closest engineering prefix. Runs entirely in your browser — nothing is uploaded.
Any SI unit: m, g, s, Pa, W, Hz… The prefix is put in front of it.
A number such as 4.7, or scientific notation such as 1.5e-9 or 2.2 × 10^6.
4.7 km = 4700 m
4700
Converted value
4.7 × 10³
Scientific notation
4.7 km
Closest engineering prefix
1 km = 1000 m
Conversion factor
Exact: a prefix is an exact power of ten, so nothing was rounded.
Your value in every prefix
| Prefix | Value |
|---|---|
| quetta (Q), 10³⁰ | 4.7 × 10⁻²⁷ |
| ronna (R), 10²⁷ | 4.7 × 10⁻²⁴ |
| yotta (Y), 10²⁴ | 4.7 × 10⁻²¹ |
| zetta (Z), 10²¹ | 4.7 × 10⁻¹⁸ |
| exa (E), 10¹⁸ | 4.7 × 10⁻¹⁵ |
| peta (P), 10¹⁵ | 4.7 × 10⁻¹² |
| tera (T), 10¹² | 4.7 × 10⁻⁹ |
| giga (G), 10⁹ | 0.0000047 |
| mega (M), 10⁶ | 0.0047 |
| kilo (k), 10³ | 4.7 |
| hecto (h), 10² | 47 |
| deca (da), 10¹ | 470 |
| no prefix, 10⁰ | 4700 |
| deci (d), 10⁻¹ | 47000 |
| centi (c), 10⁻² | 470000 |
| milli (m), 10⁻³ | 4700000 |
| micro (µ), 10⁻⁶ | 4700000000 |
| nano (n), 10⁻⁹ | 4700000000000 |
| pico (p), 10⁻¹² | 4.7 × 10¹⁵ |
| femto (f), 10⁻¹⁵ | 4.7 × 10¹⁸ |
| atto (a), 10⁻¹⁸ | 4.7 × 10²¹ |
| zepto (z), 10⁻²¹ | 4.7 × 10²⁴ |
| yocto (y), 10⁻²⁴ | 4.7 × 10²⁷ |
| ronto (r), 10⁻²⁷ | 4.7 × 10³⁰ |
| quecto (q), 10⁻³⁰ | 4.7 × 10³³ |
Prefixes attach to the gram, not the kilogram: a milligram is 10⁻³ g, and the kilogram is itself 10³ g. Binary prefixes (kibi, mebi, gibi) are a different system for computer storage.
The SI prefixes
| Prefix | Symbol | Factor | Added |
|---|---|---|---|
| quetta | Q | 10³⁰ | 2022 |
| ronna | R | 10²⁷ | 2022 |
| yotta | Y | 10²⁴ | |
| zetta | Z | 10²¹ | |
| exa | E | 10¹⁸ | |
| peta | P | 10¹⁵ | |
| tera | T | 10¹² | |
| giga | G | 10⁹ | |
| mega | M | 10⁶ | |
| kilo | k | 10³ | |
| hecto | h | 10² | |
| deca | da | 10¹ | |
| deci | d | 10⁻¹ | |
| centi | c | 10⁻² | |
| milli | m | 10⁻³ | |
| micro | µ | 10⁻⁶ | |
| nano | n | 10⁻⁹ | |
| pico | p | 10⁻¹² | |
| femto | f | 10⁻¹⁵ | |
| atto | a | 10⁻¹⁸ | |
| zepto | z | 10⁻²¹ | |
| yocto | y | 10⁻²⁴ | |
| ronto | r | 10⁻²⁷ | 2022 |
| quecto | q | 10⁻³⁰ | 2022 |
How to Use the Metric Prefix Converter
- 1. Type a value. Ordinary numbers (4.7, 0.000032) and scientific notation (1.5e-9, 2.2 × 10^6) both work, with a decimal point or comma.
- 2. Name the unit. Enter the unit symbol — m, g, s, Pa, W, Hz — to see results such as 4.7 km = 4700 m. Leave it blank to work with the prefixes alone.
- 3. Pick the prefixes. Choose the prefix you have and the prefix you want. No prefix means the plain unit. Use Swap prefixes to go the other way.
- 4. Read the result. You get the value in plain and scientific notation, the conversion factor, the closest engineering prefix, and a table of the value in all 24 prefixes. A significant-digits menu sets the rounding.
The SI Prefixes
An SI prefix multiplies a unit by a power of ten. The International System of Units defines 24, listed in the SI Brochure (9th edition, BIPM, 2019) and extended in November 2022 when the 27th General Conference on Weights and Measures added ronna (R, 10²⁷), quetta (Q, 10³⁰), ronto (r, 10⁻²⁷) and quecto (q, 10⁻³⁰). The additions follow the 1991 additions of yotta, zetta, yocto and zepto, and they reflect real needs: the world's stored data is already measured in zettabytes, and planetary and particle masses run off the old scale.
| Prefix | Symbol | Factor | Typical use |
|---|---|---|---|
| giga | G | 10⁹ | gigahertz, gigapascal |
| mega | M | 10⁶ | megawatt, megajoule |
| kilo | k | 10³ | kilometre, kilojoule |
| milli | m | 10⁻³ | millilitre, millisecond |
| micro | µ | 10⁻⁶ | micrometre, microgram |
| nano | n | 10⁻⁹ | nanometre, nanosecond |
| pico | p | 10⁻¹² | picofarad, picosecond |
Rules for Writing Prefixed Units
- Symbols are case-sensitive. M is mega and m is milli; P is peta and p is pico; Q is quetta and q is quecto. Write µ (or mu) for micro, never u in formal text.
- One prefix per unit. Write 5 nm, not 5 mµm. The kilogram is the one unit whose name already carries a prefix, so its multiples are built on the gram: a milligram is 10⁻³ g.
- The prefix belongs to the unit, so powers apply to both. 1 km² is (10³ m)², which is 10⁶ m², not 10³ m². This is the commonest source of error when converting areas and volumes.
- Leave a space between number and unit, and no space between prefix and unit symbol: 4.7 kΩ, 250 mW, 5.97 Rg.
Worked Examples
- 4.7 km is 4700 m, and the closest engineering prefix is kilo itself.
- Earth's mass, 5.97 × 10²⁴ kg, is 5.97 × 10²⁷ g, or about 5.97 ronnagrams. Jupiter, at 1.898 × 10²⁷ kg, is about 1.9 quettagrams.
- An electron's mass, 9.109 × 10⁻³¹ kg, is 9.109 × 10⁻²⁸ g, or about 0.91 rontograms.
- 1 µm is 1000 nm and 10⁻⁶ m; 1 GHz is 1000 MHz and 10⁹ Hz.
Accuracy and Limits
A prefix is an exact power of ten, so a conversion between two prefixes is exact. The converter uses integer arithmetic rather than floating point, so 0.1 µm converts to exactly 100 nm with no trailing 9s, and the result is rounded only when written out at the number of significant digits you choose. Scientific input is accepted up to 40 digits and exponents up to ±300. The converter handles the prefix, not the unit: converting between different units, such as inches and metres, is a job for the Unit Converter. Binary prefixes for computer storage — kibi, mebi, gibi, which are powers of 1024 — are a separate system, handled by the Data Storage Converter.
Frequently Asked Questions
- What are the new SI prefixes added in 2022?
- Ronna (R) means 10²⁷ and quetta (Q) means 10³⁰, while ronto (r) means 10⁻²⁷ and quecto (q) means 10⁻³⁰. They were adopted at the 27th General Conference on Weights and Measures in November 2022, the first additions since 1991. Capital letters mark the large prefixes and lower case the small ones.
- How do I convert between metric prefixes?
- Subtract the exponents. To go from kilo (10³) to milli (10⁻³), the difference is 3 − (−3) = 6, so 1 km is 10⁶ mm. In the converter, pick the two prefixes and the value; it multiplies by the exact power of ten and shows the result in plain and scientific notation.
- Why is the kilogram the exception to the prefix rules?
- The kilogram is the SI base unit of mass, and its name already contains the prefix kilo. Prefixes therefore attach to the gram, not the kilogram. A thousandth of a kilogram is a gram, and a millionth of a kilogram is a milligram — never a "millikilogram".
- What is the difference between M and m in a prefix?
- Capital M is mega, a million (10⁶), while lower-case m is milli, a thousandth (10⁻³). A 5 MW power plant is five million watts, but a 5 mW laser is five thousandths of a watt. Mixing them up is off by a factor of a billion, so check the case of the symbol.
- How do I write a number in scientific notation with an SI prefix?
- Pick the prefix whose power of ten is closest below the number's exponent, in steps of three. A mass of 4.7 × 10⁻⁵ g is 47 µg, because 10⁻⁵ is between 10⁻⁶ (micro) and 10⁻³ (milli) and 47 × 10⁻⁶ equals 4.7 × 10⁻⁵. The converter calls this the closest engineering prefix.
- How are the SI prefixes different from binary prefixes?
- SI prefixes are powers of 1000, so a gigabyte is 1 000 000 000 bytes. Binary prefixes, standardised by the IEC in 1998, are powers of 1024: a gibibyte is 1 073 741 824 bytes. Operating systems and drive makers have used the two inconsistently, which is why a 1 TB drive shows less than 1 TB on some computers.