Luminance Converter

Luminance is how bright a surface looks: the light it emits or reflects in a given direction, per unit of its area. Its SI unit is the candela per square meter (cd/m²), which is the same as the nit used for screens. Older units are the foot-lambert (fL) in US cinema and the lambert and stilb in CGS.

For a sense of scale, an office monitor is about 250–350 nits, a phone in bright mode about 1,000–2,000 nits, an HDR TV's highlights up to 1,000–4,000, and a cinema screen about 48 cd/m², the standard 14 fL.

How to convert luminance units

Type a value into any field, and every other unit is calculated at once. For example, the cinema standard of 14 fL:

1. In cd/m², or nits: multiply by 3.42626.

   14 × 3.42626 = 47.97 cd/m²

2. In cd/ft²: divide by π.

   14 / π = 4.456 cd/ft²

Common conversions

Luminance units

• Candela per square meter (cd/m²): The candela per square meter (cd/m²) is the SI unit of luminance. The unit is based on the candela, the SI unit of luminous intensity, and the square metre, the SI unit of area.
  Conversion Factor: 1 cd/m² = 1 cd/m² (Base Unit)

• Candela per square centimeter (cd/cm²): A smaller unit, used to measure the luminous intensity in candela, emitted from an area of one square centimeter.
  Conversion Factor: 1 cd/cm² = 10,000 cd/m²

• Candela per square foot (cd/ft²): Luminance can also be expressed in candela per square foot, offering an alternative unit for measuring intensity in the imperial system.
  Conversion Factor: 1 cd/ft² = 10.7639 nt

• Candela per square inch (cd/in²): Similar to cd/ft², this unit measures luminance in terms of candela per square inch.
  Conversion Factor: 1 cd/in² = 1,550.003 nt

• Stilb (sb): The stilb is a unit of luminance in the CGS system. It is defined as one candela per square centimeter.
  Conversion Factor: 1 sb = 1 cd/cm² = 10,000 cd/m²

• Lumen per square meter per steradian (lm/m²/sr): This unit represents luminous flux per unit solid angle and area. It is an equivalent unit to the candela per square meter.
  Conversion Factor: 1 lm/m²/sr = 1 cd/m²

• Lumen per square centimeter per steradian (lm/cm²/sr): An equivalent unit to the candela per square centimeter.
  Conversion Factor: 1 lm/cm²/sr = 10,000 cd/m²

• Lumen per square foot per steradian (lm/ft²/sr): An equivalent unit to the candela per square foot.
  Conversion Factor: 1 lm/ft²/sr = 1 cd/ft² = 10.7639 cd/m²

• Nit (nt): The nit is a unit of luminance equivalent to one candela per square meter.
  Conversion Factor: 1 nt = 1 cd/m²

• Millinit (mnt): This is a smaller unit, equivalent to one thousandth of a nit.
  Conversion Factor: 1 mnt = 0.001 nt = 0.001 cd/m²

• Lambert (L): The Lambert is a unit of luminance equal to 1 ⁄ π, or ≈ 0.31831 candela per square centimeter.
  Conversion Factor: 1 L = 0.31831 cd/cm² = 3,183.1 cd/m²

• Millilambert (mL): A smaller unit, representing one thousandth of a Lambert.
  Conversion Factor: 1 mL = 0.001 L = 3.1831 cd/m²

• Foot-lambert (fL): A foot-lambert is a unit of luminance used mostly in the United States. It equals to 1/π or 0.3183 candela per square foot, or 3.426 candela per square meter.
  Conversion Factor: 1 fL = 0.3183 cd/ft² = 3.426 cd/m²

Frequently asked questions

Is a nit the same as a lumen?

No. A nit (cd/m²) measures how bright a surface looks, while a lumen measures the total light a source gives out in every direction. A projector's lumens and the nits on its screen depend on the screen's size and how much light it reflects.