About this tool
The SI / Metric Prefix Converter rescales a number from one metric prefix to another for any base unit — metres, grams, hertz, watts, bytes-as-decimal, whatever you like. Enter a value, choose the source and target prefixes, and it reports the equivalent magnitude in both plain decimal and scientific notation. The optional base-unit label is purely cosmetic; the mathematics depends only on the prefixes.
Each SI prefix maps to a power-of-ten exponent, from quecto (10⁻³⁰) up through pico (10⁻¹²), nano (10⁻⁹), micro (10⁻⁶), milli (10⁻³), kilo (10³), mega (10⁶), giga (10⁹), tera (10¹²) all the way to quetta (10³⁰), and includes centi and deci. The result is value × 10^(exponent[from] − exponent[to]). For example 1500 (none) is 1.5 kilo, and 2.5 giga is 2500 mega. The full 2022 revision of the SI prefixes (quecto, ronto, ronna, quetta) is included.
To keep long conversions exact, the decimal result is produced by shifting the decimal point of your input string rather than by floating-point multiplication, so a value spanning many orders of magnitude does not accumulate rounding error. Everything is computed locally in your browser. This is the fast way to move between micrograms and milligrams, kilohertz and megahertz, or nanometres and metres without counting zeros by hand.