Illuminance (Light) Converter
Convert between lux and foot-candles for measuring light levels.
How illuminance conversion works
Illuminance measures how much light falls on a surface — different from luminance (how bright a surface appears) or luminous intensity (a light source's total output). Lux is the metric unit; the foot-candle is the older imperial equivalent, still used in some US lighting and photography contexts.
Reference light levels
- Direct sunlight: roughly 100,000 lux (≈ 9,290 foot-candles)
- A well-lit office: roughly 300–500 lux (≈ 28–46 foot-candles)
- Full moonlight: roughly 0.1–0.3 lux
- 1 foot-candle ≈ 10.76 lux
Frequently asked questions
Why is it called a 'foot-candle'?
It historically represents the illuminance produced by one standard candle at a distance of one foot — an old but still-used unit predating standardized metric lighting measurement.
What's the difference between illuminance and brightness?
Illuminance (lux, foot-candles) measures light falling onto a surface from a light meter's perspective, while perceived brightness also depends on the surface's reflectivity and color — two surfaces under identical illuminance can look very differently bright.