Lux / Footcandle Converter and Lumen Method
Exact lux <-> footcandle conversion and the lumen-method average maintained illuminance from luminaire lumens.
Example
You enter
- Mode convert
- Footcandles (convert mode) 100
You get
- Footcandles 100 fc
- Lux 1076.4
Checked against published worked examples from: IES Lighting Handbook (lumen method) + exact lux/footcandle unit identity.
Details, formula, and sources
ScopeCoefficient of utilization, and light-loss factor.
Formula or tablefc = lux / 10.764 (1 footcandle = 1 lumen/ft^2; 1 lux = 1 lumen/m^2; 1 ft^2 = 0.092903 m^2). Lumen method (room average): fc = (total lumens × CU × LLF) / area_ft2, where CU is the coefficient of utilization and LLF the light-loss factor.
Source and editionIES Lighting Handbook (10th ed.) lumen method, by name; the 10.764 lux-per-footcandle conversion is an exact unit identity.
Free accessIES Handbook licensed; the conversion identity and the lumen-method formula are public and reproduced in any lighting-design text.
What governsEstimate. AHJ and licensed professional govern.
API field namesmode, footcandles, lux
- Conversion constant 1 fc = 10.76391 lux (exact identity from 1 ft = 0.3048 m; 10.764 rounded)SI/US-customary unit identity
- CU / LLF coefficient of utilization and light-loss factor are project-specific and user-supplied from the luminaire photometric report and maintenance scheduleIES Lighting Handbook lumen method