Foot-Lambert calculator

is a unit of luminance (the intensity of light emitted from a surface). It is the luminance of a perfectly diffusing surface emitting or reflecting 1 lumen per square foot. This unit is used in the US and Canada, and worldwide in the cinema business.
     To directly input luminance values, click here
Diagonal (SI)
Screen size (SI)
23.19m x 9.87m
Screen surface (SI)
Diagonal (imperial)
82.68 ft
Screen size (imp)
76.08ft x 32.37ft
Screen surface (imp)
2462.78 sq.ft.
44.5 nit
Exposure Value
8.48 EV

     Acceptable for rooms with little ambient light. E.g. cinema screens aim for 14-16 ftL.

Screen luminance: EV8.48

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starlight to dim ambient lightmoon eclipse to night home interiorneon lights to landscape after sunsetbright light to weak sunbright daylight to direct sunlight


A foot-lambert or footlambert (ftL, sometimes fl or ft-L) is a unit of luminance. For screens that are projected upon (like cinema, home cinema), it quantifies how much light is reflected (to the center of the room). This depends on the amount of light produced (lumens), the size of the screen and the screen gain.