F-number is a measure of the light-gathering ability of an optical system such as a camera lens.
F-number may also refer to:
F number (chemistry), a correlation number in the analysis of polycyclic aromatic hydrocarbons Fujita scale, a rating of a tornado's intensity by its impact on structures and vegetation Filial number in the cross-breeding of hybrid animals
See also F-ratio (disambiguation) F scale (disambiguation) F1 (disambiguation) F2 (disambiguation) F3 (disambiguation) F15 (disambiguation) F150 (disambiguation)