How this conversion works
Luminance describes how bright a surface or screen appears: luminous intensity (candelas) per unit area. The SI unit is the candela per square meter, often called a nit.
The foot-lambert, lambert and apostilb include a factor of 1/π from their historical definition for perfectly diffusing surfaces. For example, 1 fL = (1/π) cd/ft² ≈ 3.426 cd/m².
Formula: result = value × (base units per source unit) ÷ (base units per target unit)
Where this conversion is used
- Screen and TV brightness specifications in nits.
- Cinema projection standards that use foot-lamberts.
- Signage and display readability comparisons.
Worked example: 100 nits to foot-lamberts
- 1 fL ≈ 3.426259 cd/m².
- 100 ÷ 3.426259 = 29.19 fL.
Unit definitions
| Unit | In candelas per square meter | Note |
|---|---|---|
| Candela per square meter (nit) (cd/m²) | 1 | |
| Candela per square centimeter (stilb) (cd/cm²) | 10,000 | |
| Candela per square foot (cd/ft²) | 10.7639104167 | |
| Candela per square inch (cd/in²) | 1,550.00310001 | |
| Foot-lambert (fL) | 3.4262590996 | (1/π) cd/ft². |
| Lambert (L) | 3,183.09886184 | (1/π) cd/cm². |
| Apostilb (asb) | 0.3183098862 | (1/π) cd/m². |
Candelas per square meter to foot-lamberts
| Candela per square meter (nit) (cd/m²) | Foot-lambert (fL) |
|---|---|
| 1 | 0.2919 |
| 48 | 14.0094 |
| 100 | 29.1864 |
| 250 | 72.9659 |
| 500 | 145.9318 |
| 1,000 | 291.8635 |
Foot-lamberts to candelas per square meter
| Foot-lambert (fL) | Candela per square meter (nit) (cd/m²) |
|---|---|
| 1 | 3.4263 |
| 14 | 47.9676 |
| 16 | 54.8201 |
| 30 | 102.7878 |
| 50 | 171.313 |
Precision and sources
Results are calculated from the definitions above and rounded to 12 significant digits; the converter shows up to eight decimal places and the tables four. Reference: NIST Special Publication 811, Guide for the Use of the International System of Units, Appendix B.
Frequently asked questions
Are nits the same as lumens?
No. Nits (cd/m²) describe the brightness of a surface. Lumens measure total light output from a source.
What is the difference between luminance and illuminance?
Luminance is light leaving or reflected from a surface toward the eye; illuminance is light arriving on a surface. Use the Illuminance Converter for lux and foot-candles.