The complete list of SI prefixes from quetta down to quecto with symbols, powers of ten, decimal factors and a familiar example of each.. SI Unit Prefix Table is a free online tool from the ToolsRift Study & Education Tools collection. It runs entirely in your browser — nothing to install, no signup, and your data never leaves your device.
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How to use SI Unit Prefix Table
Search or browse the full table of SI prefixes and read off the symbol, power of ten, decimal factor and example for each. Use the converter below it to move a value between any two prefixes.
Frequently asked questions
How many SI prefixes are there?
Twenty-four, running from quetta at ten to the thirtieth down to quecto at ten to the minus thirtieth. Ronna, quetta, ronto and quecto were added by the General Conference on Weights and Measures in 2022, mainly to cope with data storage and particle-scale measurements.
Which prefixes use capital letters?
Every prefix from mega upward uses a capital symbol — M, G, T, P, E, Z, Y, R, Q — while kilo and below use lowercase, apart from the special case that kilo is a lowercase k. Getting this wrong matters: mK and MK differ by nine orders of magnitude.
Are kibi and mebi the same as kilo and mega?
No. The binary prefixes kibi, mebi and gibi mean 1024, 1024² and 1024³, while the SI kilo, mega and giga always mean powers of a thousand. That is why a 1 TB drive shows as about 931 GiB in an operating system.
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