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
The conversion factor
The tool treats one foot-candle as 10.76391 lux. Lux is the base unit, so foot-candles are multiplied by 10.76391 to reach lux, and lux is divided by 10.76391 to reach foot-candles. Converting a unit to itself returns the same number. Results update as you type, starting from a default of 500 lux.
Worked examples
- 500 lux = 46.451522 foot-candles (the default conversion).
- 50 foot-candles = 538.1955 lux.
- 1 lux = 0.092903 foot-candles, so one foot-candle is roughly eleven times brighter than one lux.
- 100,000 lux = 9,290.30436 foot-candles, the direct-sunlight reference level listed above.
Checking the reference levels above
- 300 lux converts to 27.870913 foot-candles and 500 lux to 46.451522, so the office range of 300–500 lux is about 28–46 foot-candles.
- Moonlight at 0.1 lux is 0.00929 foot-candles, and at 0.3 lux it is 0.027871.
- Going the other way, 1 foot-candle is 10.76391 lux and 10 foot-candles is 107.6391 lux.
Precision and what is not covered
Up to six decimal places are shown and then trimmed. A very small input such as 0.0000001 lux is displayed as 0 foot-candles. Digit grouping follows your browser's locale, so thousands separators may look different on your device. Negative numbers are accepted and converted as typed.
Only lux and foot-candles are offered. The tool cannot turn lumens into lux, because that also needs the area the light spreads over, and it does not handle luminance units such as nits.
More conversions, and what not to enter
300 lux is 27.870913 foot-candles, 1,000 lux is 92.903044 foot-candles, 20 foot-candles is 215.2782 lux, and 0.5 foot-candle is 5.381955 lux. Converting a unit to itself returns the same number, so 50 lux to lux is 50.
Enter the reading from a light meter, which shows illuminance. The lumen rating on a bulb's packaging is a different quantity, the total light the bulb gives out, and it cannot be converted to lux without knowing the area it spreads over.
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.
How many foot-candles is a 300 lux office?
300 ÷ 10.76391 gives about 27.87 foot-candles. The converter shows the figure to six decimals.
Can I convert lumens to lux here?
No. Lumens measure total light output, while lux is light per square meter on a surface. Going between them needs an area, which this converter does not ask for.
Why does my tiny value come out as 0?
Results are limited to six decimal places, so numbers smaller than about 0.0000005 in the target unit round down to zero.