Unit Conversion

Convert numbers between two units quickly and precisely

Illuminance

Unit Conversion

Convert illuminance units: lux, phot, and footcandle

Illuminance states how much light falls on a surface and is stated in lux (lx), the SI unit, as well as kilolux (klx) for high illuminance levels. In the older CGS system, phot (ph) is common; in the US, footcandle (fc).

Key conversion factors:

  • 1 kilolux (klx) = 1,000 lux
  • 1 phot (ph) = 10,000 lux
  • 1 footcandle (fc) = 10.764 lux
  • Midday sunlight: approx. 100,000 lux · Office lighting: 300 to 500 lux

Applications:

  • Lighting design & architecture: designing workplace and interior lighting
  • Photography: measuring available light at a shooting location
  • Workplace safety: complying with required minimum illuminance levels

The illuminance converter supports lighting design and comparing light sources. For the total light output of a lamp, use the luminous flux converter.

Frequently asked questions about converting illuminance

300 to 500 lux is usually recommended for office workstations, while direct midday sunlight reaches about 100,000 lux – roughly 200 to 300 times as much. This shows how wide the range of the lux scale is in everyday life.

1 footcandle (fc) equals 10.764 lux. Footcandle is mainly used in the US, while lux is the internationally common SI unit for illuminance.

Lumen (luminous flux) describes the total amount of light emitted by a light source, while lux (illuminance) describes how much of that reaches a given surface: 1 lux = 1 lumen per square meter. For the pure luminous flux of a lamp, use the luminous flux converter.