SI Prefix Converter
Convert a value between SI prefixes (quetta to quecto) exactly, with scientific and engineering notation and a table of the value under every prefix.
The value under the prefix you choose, its scientific and engineering forms, and the same value in all 24 SI prefixes — an exact power-of-ten shift with no float drift.
Example: 2.5 km is 2,500,000 mm and 2.5 × 10³ m; 0.000047 m is 47 µm; 123.456 nm is 1.23456 × 10⁻⁷ m. The 2022 prefixes ronna, quetta, ronto and quecto are included.
Powers of ten,
shifted exactly.
The prefix table used, how the shift is done without float drift, and the two notations.
The prefixes
The SI Brochure defines 24 prefixes from quecto (10⁻³⁰) to quetta (10³⁰); ronna, quetta, ronto and quecto were added by the 27th CGPM in 2022. Converting between two of them multiplies the value by 10 to the difference of their exponents — nothing else, which is why the page needs no unit knowledge and the unit symbol is only a label.
Exactness
Multiplying a binary float by 1000 repeatedly accumulates rounding error (0.1 × 1000 is not exactly 100 in floating point). The page instead rewrites the number in decimal scientific form and shifts its exponent, so 123.456 nm becomes exactly 1.23456 × 10⁻⁷ m.
Scientific vs engineering
Scientific notation has one digit before the point (4.7 × 10⁻⁵); engineering notation uses exponents that are multiples of three so the number reads with a prefix (47 × 10⁻⁶ = 47 µ). The kilogram is the base unit of mass even though it carries a prefix; binary prefixes (kibi, mebi) are a separate IEC system and are not mixed in here. Nothing leaves the browser; the same four anonymous usage counts as the rest of the site apply.
SOURCES
Last reviewed 20 September 2026. How results are checked: How we verify.