Luminance Conversion Calculator
Written by Thierno Sadou Diallo, formula verified per our methodology • Last checked on 9/10/2026
To convert a luminance, it is reduced to candelas per square meter (cd/m², also called nit), then converted into the target unit. A luminance of 100 cd/m² equals about 29.19 foot-lamberts.
Explanation
Luminance measures the light intensity emitted or reflected by a surface, as perceived by an eye or sensor looking at it — not to be confused with illuminance, which instead measures the light RECEIVED by a surface (in lux, governed by the inverse-square law as distance from the source changes), a different photometric quantity even though the two are often confused in everyday language. The candela per square meter (cd/m²), also called a nit in the display industry (both units are strictly identical, only the name changes), is the reference unit for characterizing a screen's brightness: a modern smartphone often exceeds 500 to 1000 nits in direct sunlight, while a typical desktop monitor sits more around 250 to 350 nits. The stilb, a CGS-system unit, equals exactly 10,000 cd/m² (1 cd/cm², a simple metric rescaling) and is still encountered in certain historical scientific contexts. The lambert and foot-lambert, on the other hand, incorporate a factor of 1/π inherited from Lambert's law of perfectly diffuse emission (a surface that emits or reflects light uniformly in all directions): 1 lambert equals about 3183.1 cd/m², and 1 foot-lambert about 3.43 cd/m², the latter unit still used in the United States, notably to characterize the perceived brightness on a cinema screen.
Example: converting 100 cd/m² to foot-lamberts
Inputs
Value: 100. Starting unit: candelas per square meter. Target unit: foot-lamberts.
Calculation
100 cd/m² ÷ [(1/π) ÷ 0.3048²] ≈ 100 ÷ 3.42626 ≈ 29.186 foot-lamberts.
Result
100 cd/m² equals about 29.19 foot-lamberts.
Frequently asked questions
Are nit and cd/m² really the same unit?
Yes, strictly: the nit is just an alternative name, shorter and more common in the display industry (screens, TVs, smartphones), for the candela per square meter. Converting between the two therefore means multiplying by exactly 1 — no factor is involved, unlike the other units on this page.
Where does the 1/π factor in the lambert and foot-lambert come from?
This factor comes from Lambert's law of perfectly diffuse emission: a perfectly diffusing (Lambertian) surface that emits a given luminous flux per unit area spreads that flux over a specific angular distribution, and the relationship between that total flux and the luminance perceived from a given direction involves a factor of π. The lambert and foot-lambert build this factor directly into their definition, unlike the nit or stilb, which do not account for it.
What is the difference between luminance and illuminance?
Luminance characterizes the light leaving a surface, toward the eye or sensor observing it (this is what determines whether a screen looks bright); illuminance, in lux, instead characterizes the light arriving at a surface (this is what determines whether a room or workstation is adequately lit) — and it's precisely this arriving light our room lighting wattage calculator helps size for. A single light source therefore produces an illuminance on the surfaces it lights up, and each of those surfaces then has its own luminance depending on its reflectivity.