candela per square metre

candela per square metre

SI coherent derived unit
Name Symbol Derived quantity
candela per
square metre
m−2 cd luminance


The candela per square metre, symbol m−2 cd, is the SI coherent derived unit of luminance.


Luminance is a photometric measure of the luminous intensity per unit area of light travelling in a given direction. It describes the amount of light that passes through, is emitted or reflected from a particular area, and falls within a given solid angle.

Photometry units

Name Symbol Quantity Expressed in terms of SI base units Expressed in terms of other SI units
candela cd luminous intensity cd lm/sr
lumen lm luminous flux cd cd sr
lux lx illuminance m-2 cd lm/m2
candela per square metre m-2 cd luminance m-2 cd cd/m2
lumen second lm s luminous energy s cd lm s
lumen per watt lm W‑1 luminous efficacy kg‑1 m‑2 s3 cd lm/W