Popular illuminance conversions
About illuminance units
Illuminance is the amount of light falling on a surface. Offices are lit to about 300–500 lux; direct sunlight can exceed 100,000 lux. One foot-candle (one lumen per square foot) is about 10.764 lux.
Illuminance unit reference
| Unit | Symbol | Value in lx | System |
|---|---|---|---|
| Lux | lx | 1 lx | SI |
| Kilolux | klx | 1,000 lx | SI |
| Foot-candle | fc | 10.76391 lx | US customary |
| Phot | ph | 10,000 lx | CGS |
| Nox | nx | 0.001 lx | Other |
| Lumen per square inch | lm/in² | 1,550.0031 lx | US customary |
Frequently asked questions
What is the SI unit of illuminance?
This converter uses the lux (lx) as its reference unit; every other unit is defined relative to it.
How many illuminance units can I convert?
6 units are supported here, across SI, US customary, CGS, Other systems. Every pair can be converted in both directions.
Does this illuminance converter work offline?
Yes. Once the page has loaded, every calculation runs locally in your browser — nothing is sent to a server.