One lux is one lumen per square meter. It is the international unit for light levels, used on meters, codes and calculation outputs. A full moon gives about 0.25 lux, a living room 50 to 150, an office 300 to 500, an operating table tens of thousands. One foot-candle equals about 10.76 lux, and designers working across markets often round it to 10.
Client wants 500 lux maintained at the desks, so with a 0.8 light loss factor we design to about 625 initial.
Also heard as
- lx
- lumens per square meter
Related terms
Illuminance
The amount of light falling on a surface per unit area, measured in lux or foot-candles.
Foot-candle
The North American working unit of light on a surface: one lumen falling evenly on each square foot.
Lumen
The unit of total visible light leaving a source, with each wavelength counted by how bright it looks to the eye.
Light loss factor
A multiplier, usually 0.7 to 0.9, applied to initial light levels to predict what the system delivers after aging and dirt.