Luminance Converter
Convert luminance between cd/m², nits, candela per square foot, stilb, apostilb, lambert and foot-lambert. Pick any source and target unit and get an exact result instantly.
Luminance Formula
Every luminance unit on this page is defined as a fixed multiple of the SI unit, candela per square meter (cd/m²). To convert, change the value to cd/m² with the factor of the source unit, then divide by the factor of the target unit. Both steps combine into one formula, and the tool does it without rounding in between. Units based on π (apostilb, lambert, foot-lambert) use the full value of π.
What Is Luminance?
Luminance describes how bright a surface looks when you view it from a particular direction. It is the luminous intensity of a surface per unit of projected area, measured in candela per square meter (cd/m²) in the SI system. A glowing screen, a lit wall or a road surface under headlights can all be described with a luminance value.
The older name for cd/m² is the nit, and many display makers still quote brightness in nits. Luminance is not the same as illuminance: illuminance (lux) measures the light that lands on a surface, while luminance measures the light that leaves it toward your eyes. Our Illumination Converter covers lux and foot-candles, and the Luminous Intensity Converter covers candela.
Other units appeared with older measurement systems. The stilb and lambert come from the CGS system, and the foot-lambert is common in the US film and lighting industries. Lambert-based units are defined using π because they describe an ideal, perfectly diffuse (Lambertian) surface.
Supported Luminance Units
Every unit below is converted through its exact definition in cd/m².
| Unit | Symbol | 1 unit equals (in cd/m²) | Basis |
|---|---|---|---|
| Candela per square meter | cd/m² | 1 cd/m² | SI unit |
| Nit | nt | 1 cd/m² | Exactly 1 cd/m² |
| Kilocandela per square meter | kcd/m² | 1,000 cd/m² | Exact |
| Lumen per square meter per steradian | lm/(m²·sr) | 1 cd/m² | Exactly 1 cd/m² |
| Candela per square centimeter | cd/cm² | 10,000 cd/m² | Exact |
| Candela per square foot | cd/ft² | 10.7639104167 cd/m² | Exact (1 ÷ 0.09290304) |
| Candela per square inch | cd/in² | 1,550.00310001 cd/m² | Exact (1 ÷ 0.00064516) |
| Stilb | sb | 10,000 cd/m² | Exactly 1 cd/cm² |
| Apostilb | asb | 0.318309886184 cd/m² | Exact (1 ÷ π) |
| Skot | sk | 0.000318309886184 cd/m² | Exact (0.001 ÷ π) |
| Lambert | L | 3,183.09886184 cd/m² | Exact (10,000 ÷ π) |
| Millilambert | mL | 3.18309886184 cd/m² | Exact (10 ÷ π) |
| Foot-lambert | fL | 3.42625909964 cd/m² | Exact (1 ÷ (π × 0.09290304)) |
How to Use the Luminance Converter
- Type the luminance value in the input box. Decimals and scientific notation such as 2.5 or 1e-3 are accepted.
- Choose the unit you are converting from, then the unit you want to convert to.
- The result appears at once, along with the same value in every other supported unit. Press Convert Now if you prefer to confirm manually.
- Use Swap Units to reverse the conversion, Scientific notation for very large or small values, Copy Result to copy the answer, or Reset to start over.
Luminance cannot be negative, so negative values show an error message.
Practical Examples
- Cinema screen: the standard digital cinema screen luminance of 14 fL equals 47.9676273949 cd/m² (about 48 nits).
- Monitor brightness: a display set to 250 cd/m² is 72.96587699 fL and 23.22576 cd/ft².
- CGS unit: 0.5 stilb = 0.5 × 10,000 = 5,000 cd/m².
- Lambert: 1 lambert = 3,183.09886184 cd/m², which is 10,000/π.
- Apostilb: 100 asb = 100/π = 31.8309886184 cd/m².
Luminance – Common Values
Quick reference for frequently used conversions
| cd/m² (nit) | cd/ft² | Stilb | Apostilb | Lambert | Foot-lambert |
|---|---|---|---|---|---|
| 0.1 | 0.009290304 | 0.00001 | 0.314159265359 | 0.0000314159265359 | 0.029186350796 |
| 1 | 0.09290304 | 0.0001 | 3.14159265359 | 0.000314159265359 | 0.29186350796 |
| 10 | 0.9290304 | 0.001 | 31.4159265359 | 0.00314159265359 | 2.9186350796 |
| 48 | 4.45934592 | 0.0048 | 150.796447372 | 0.0150796447372 | 14.0094483821 |
| 80 | 7.4322432 | 0.008 | 251.327412287 | 0.0251327412287 | 23.3490806368 |
| 100 | 9.290304 | 0.01 | 314.159265359 | 0.0314159265359 | 29.186350796 |
| 250 | 23.22576 | 0.025 | 785.398163397 | 0.0785398163397 | 72.96587699 |
| 300 | 27.870912 | 0.03 | 942.477796077 | 0.0942477796077 | 87.559052388 |
| 1,000 | 92.90304 | 0.1 | 3,141.59265359 | 0.314159265359 | 291.86350796 |
| 10,000 | 929.0304 | 1 | 31,415.9265359 | 3.14159265359 | 2,918.6350796 |
Real-Life Applications of Luminance Conversion
- Displays and TVs: screen brightness and HDR peak brightness are quoted in cd/m² or nits. Reference monitors for color work are often calibrated to around 80 to 120 cd/m².
- Cinema and projection: screen brightness is specified in foot-lamberts in the US and in cd/m² elsewhere, so projection standards need converting.
- Road and tunnel lighting: road surface luminance is designed and measured in cd/m².
- Photography and film: spot meters and light measurement tools may report in different luminance units.
- Aviation and instrument panels: cockpit and automotive displays need readable brightness in daylight and at night.
- Reading older documents: technical papers and data sheets may still use stilb, lambert or apostilb.