Convert luminance units — candela/m², nit, stilb, foot-lambert and more.
| Unit | Name | Value |
|---|---|---|
| cd/m² | Candela/Square Meter | 10.7639 |
| nt | Nit | 10.7639 |
| sb | Stilb | 0.00107639 |
| L | Lambert | 0.0033815777 |
| fL | Foot-lambert | 3.1415888 |
| cd/in² | Candela/Square Inch | 0.0069444516 |
Formula: Lambert = Candela/ft² × 0.003382
Multiply any Candela/ft² value by 0.003382 to get Lambert.
Reverse: Candela/ft² = Lambert × 295.7
Common luminance values — factor: 1 cd/ft² = 0.003382 L
| Candela/ft² (cd/ft²) | Lambert (L) | Context |
|---|---|---|
| 0.001 cd/ft² | 3.382e-06 L | Dark |
| 0.01 cd/ft² | 3.382e-05 L | Very dim |
| 0.1 cd/ft² | 0.0003382 L | Dim |
| 1 cd/ft² | 0.003382 L | 10.76 nit |
| 4.47 cd/ft² | 0.01512 L | 48 nit — cinema |
| 9.29 cd/ft² | 0.03141 L | 100 nit |
| 10 cd/ft² | 0.03382 L | 107.6 nit |
| 50 cd/ft² | 0.1691 L | 538 nit |
| 100 cd/ft² | 0.3382 L | 1,076 nit |
| 186 cd/ft² | 0.629 L | 2,000 nit phone |
| 500 cd/ft² | 1.691 L | 5,382 nit |
| 1000 cd/ft² | 3.382 L | 10,764 nit |
| 1e+04 cd/ft² | 33.82 L | 107,639 nit |
| 1e+05 cd/ft² | 338.2 L | 1 Mnit |
| 1e+06 cd/ft² | 3382 L | 10 Mnit |
1 cd/ft² = 0.003382 L.
nit = cd/m² exactly. Use this as the bridge between SI and legacy units.
Multiply result by 295.7 to recover the original cd/ft² value.
Specifies monitor, TV, and smartphone panel brightness in nits (cd/m²) for HDR grading and product specs.
Calibrates projector output to SMPTE standard of 14 foot-Lamberts for optimal image quality.
Calculates luminance of illuminated surfaces in cd/m² to evaluate glare and visual comfort.
Designs head-up displays exceeding 10,000 nits for daylight readability.
Converts between legacy (Lambert, stilb) and SI (cd/m²) units when reviewing historical data.
Specifies outdoor LED sign brightness in nits for visibility across ambient lighting conditions.
Candela per square foot (cd/ft²) is an Imperial luminance unit equal to approximately 10.764 cd/m². It is used in US lighting engineering for specifying surface luminance of illuminated panels, signage, and architectural lighting elements.
Architectural lighting specifications in North America sometimes use cd/ft² for luminaire surface luminance limits (to control glare) and for evaluating light trespass onto adjacent properties. Exit signs and emergency lighting luminance requirements may be stated in cd/ft².
Interesting fact: The difference between cd/ft² and foot-Lamberts reflects whether the surface is treated as a perfect diffuser: 1 fL = (1/π) cd/ft², while 1 cd/ft² = π fL. The distinction matters for calculating luminance of non-Lambertian (specular or textured) surfaces.
The Lambert (L) is a CGS unit of luminance equal to 1/π candela per square centimeter ≈ 3,183 cd/m². It was defined by the German mathematician Johann Heinrich Lambert, whose work on photometry in the 1760s established the foundations of the science.
The Lambert was the standard photometric unit in North American optical engineering through the mid-20th century. Film screen luminance was specified in Lamberts; the SMPTE standard for cinema projection is 14 foot-Lamberts ≈ 48 cd/m².
Interesting fact: The Lambert is defined using 1/π because a perfectly diffuse (Lambertian) surface reflecting 1 lumen per cm² has a luminance of exactly 1/π cd/cm². This mathematical convenience made it the natural unit for Lambertian radiators.
Luminance measures how bright a surface appears to a human observer. The SI unit is cd/m² (identical to the nit used in display industry). Older units — Lambert, foot-Lambert, and stilb — remain in cinema, photometry, and legacy specs. Key anchors: 100 cd/m² = SDR reference; 1,000 cd/m² = HDR10 peak; 14 fL = 48 cd/m² = SMPTE cinema standard.
Exact factor: 1 cd/ft² = 0.003382 L. Reverse: 1 L = 295.7 cd/ft².
All conversions use IEEE 754 double-precision arithmetic, accurate to at least 8 significant figures.