Illumination Converter
Convert between lux, foot-candles, lumens per square metre and phot.
What the Illumination Converter does
Illuminance measures light falling on a surface. One lux is one lumen per square metre. Office lighting typically targets 300–500 lux; overcast daylight is around 1,000 lux and direct sunlight exceeds 100,000.
Formula
Convert to lux, then divide by the target unit's factorResult = Value × (from factor ÷ to factor)
Inputs explained
| Input | Unit | Required | Notes |
|---|---|---|---|
| Value | number | Yes | — |
| From | one of 4 options | Yes | — |
| To | one of 4 options | Yes | — |
How to use it
- Choose From and To.
- Enter Value.
- Select Calculate.
Worked example
Convert a 500 lux office target to foot-candles.
- Value
- 500
- From
- Lux
- To
- Foot-candle
500 ÷ 10.764 = 46.5 fc.
Reading the result
- Illuminance is light arriving at a surface. Office work wants 300–500 lux, close detail work 750–1,000, overcast daylight is around 1,000 and direct sun exceeds 100,000.
- A foot-candle is one lumen per square foot, which works out at about 10.76 lux.
Common mistakes
- Choosing a lamp on lumens alone. Lumens measure the light a source emits; lux is what reaches the surface, and it falls with the square of the distance.
- Comparing readings taken at different distances or angles, since illuminance depends on both.
Frequently asked questions
What is the difference between lumens and lux?
Lumens measure total light output from a source. Lux measures how much of it lands on a square metre of surface, so it falls off with distance.