| Femtometre | |
|---|---|
 The helium atom and perspective magnitudes | |
| General information | |
| Unit system | SI |
| Unit of | length |
| Symbol | fm |
| Conversions | |
| 1 fm in ... | ... is equal to ... |
| SI base units | 1×10−15 m |
| Natural units | 6.1877×1019 ℓP 1.8897×10−5 a0 |
| imperial/US units | 3.9370×10−14 in |
The femtometre (American spelling femtometer), symbol fm,[1][2] (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 naturalized to American physicist Enrico Fermi, as it is a typical length-scale of nuclear physics.
- ^ "Units: F". Unc.edu. Archived from the original on 2018-07-09. Retrieved 2015-11-04.
- ^ "Nuclear Size and Shape" (PDF). Archived from the original on 2012-04-25.
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