The femtometre (American spelling femtometer) symbol fm derived from the Danish and Norwegian word femten 'fifteen', Ancient Greek: μέτρον, romanized: metrοn, lit. 'unit of measurement') is a unit of length in the International System of Units (SI) equal to 10−15 metres, which means a quadrillionth of one metre. This distance is sometimes called a fermi and was so named in honour of Italian-American physicist Enrico Fermi, as it is a typical length-scale of nuclear physics.
|1 fm in ...||... is equal to ...|
|SI base units||1×10−15 m|
|Natural units|| 6.1877×1019 ℓP|
|imperial/US units||3.9370×10−14 in|