Lux (lx) is the metric unit of illuminance: one lumen of light falling on one square meter of surface. It is the standard measure of light level across most of the world.
How lux is measured
One lux equals one lumen per square meter. A light meter reads it at the work plane, the surface where the task takes place. The same lamp produces fewer lux over a larger area.
Lux versus foot-candles
Foot-candles are the US customary equivalent. One foot-candle is about 10.764 lux, so divide lux by 10.764 to get foot-candles.
| Space | Typical level |
|---|---|
| Corridors | 100 lux |
| General office | 300 to 500 lux |
| Detailed tasks | 750 to 1,000 lux |
| Retail | 500 to 750 lux |
| Warehouse | 100 to 200 lux |
See the Lux Calculator and the Recommended Lux Levels.
How lux is used
Lux quantifies how much light actually reaches a surface, which is what matters for seeing a task — unlike lumens, which measure a source’s total output regardless of where it lands. One lux is one lumen spread over one square metre, so the same bulb gives high lux on a small desk and low lux across a large room. Typical targets: ~50 lux for a hallway, 150–300 lux for living areas, 300–500 lux for offices and kitchens, and 500–750+ lux for detailed work. Because illuminance falls off with the square of distance, doubling the distance from a source cuts the lux to a quarter.
Lux vs lumens? Lumens are output at the source; lux is what lands on the surface. Lux vs foot-candles? One foot-candle is about 10.76 lux.