Fermi (fm) is a metric unit of Distance before used in atomic physics. 1 fermi equals 10-15 meter, or 1 femtometer. The entity is named for Enrico Fermi (1901-1954), the Italian-American physicist who built the first nuclear reactor. There was a need for this entity before the metric prefixes for very small amounts were identified; now distances formerly calculated in fermis are stated in femtometers instead.

You can use our length converter tool to convert fermi to other length units.