F-ratio or f-ratio may refer to: * The F-ratio used in statistics, which relates the variances of independent samples; see

F-distribution In probability theory and statistics, the ''F''-distribution or ''F''-ratio, also known as Snedecor's ''F'' distribution or the Fisher–Snedecor distribution (after Ronald Fisher and George W. Snedecor), is a continuous probability distribut ...

* f-ratio (oceanography), which relates recycled and total primary production in the surface ocean *

f-number An f-number is a measure of the light-gathering ability of an optical system such as a camera lens. It is calculated by dividing the system's focal length by the diameter of the entrance pupil ("clear aperture").Smith, Warren ''Modern Optical ...

, f-ratio, or focal ratio, the ratio of the focal length of an optical system to the diameter of its entrance pupil

See also