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 distribution ...

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

f-number In optics, the f-number of an optical system such as a camera lens is the ratio of the system's focal length to the diameter of the entrance pupil ("clear aperture").Smith, Warren ''Modern Optical Engineering'', 4th Ed., 2007 McGraw-Hill Pro ...

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

See also