Lux to Watts Calculator

Illuminance in lux (lx) to electric power in watts (W) calculator.

Lux is the accepted scientific term for illumination, but the corresponding unit in English and American traditional units is the foot-candle. One Lux is the amount of illumination for 1 lumen per square meter. One foot candle is the amount of illumination for 1 lumen per square foot, or about 10.764 lux which is the number of square feet per square meter. Since one foot-candle is the illuminance cast on a surface by a one-candle source one foot away, a lux could be thought of as a "meter-candle", although this term is discouraged because it does not conform to SI standards for unit names, mainly because candles vary in size (wick size) and amount of light emmitted from the flame, i.e, smaller flame, smaller amount of light.

The foot-candle is commonly used in lighting layouts in parts of the world where United States customary units are used, mainly the United States.  Recommended Illuminance Values for Generic Types of Activities in Interiors

Enter the illuminance in lux, luminous efficacy in lumens per watt, surface area in square feet / meters or spherical radius in feet / meters and press the Calculate button to get the power in watts:

Enter illuminance in lux lx
Select light source
Or enter luminous efficacy in lumens per watt lm/W
Enter surface area
Or enter spherical radius
Power  result in watts W