Luminance Converter

Luminance measures how bright a surface looks to the eye, counting the light it emits or reflects toward you per unit area. It’s the counterpart to illuminance: illuminance is light arriving at a surface, luminance is light leaving it. The SI unit is the candela per square meter (cd/m²).

Key conversions:

• 1 nit = 1 cd/m² (nit is just an older name for the same unit)
• 1 foot-lambert = 3.4263 cd/m²
• 1 lambert = 3,183.1 cd/m² (10,000/π cd/m²)

If you’ve shopped for a TV or monitor, you already know luminance by its marketing name, the nit. Every “1,000-nit HDR” claim is a luminance figure, and converting nits to cd/m² is free because they’re the same thing.

Brightness you can picture:

• A typical computer monitor: 200–500 cd/m²
• An HDR display at peak: 1,000 cd/m² and up
• An overcast sky: around 2,000 cd/m²
• Fresh snow in sunlight: over 10,000 cd/m²

The lambert family (foot-lambert, lambert) lingers in cinema and older photometry, where screen brightness was historically measured that way. The π buried in the lambert isn’t arbitrary; it falls out of assuming a perfectly diffuse surface that scatters light evenly in every direction.

A peak-brightness number on a spec sheet rarely tells the whole story. A screen that hits 1,000 nits on a small highlight but averages 400 across the full panel will look dimmer in a sunlit room than the headline promises.