Maintained average illuminance calculator

The lumen method estimates maintained average work-plane illuminance from fixture output, utilization and losses.

Units

E_{\text{fc}} = \frac{N \times L \times \mathrm{CU} \times \mathrm{LLF}}{A}

Calculator

Enter the values you know and leave one box empty. Calculate finds the empty one, the result or any input.

Given

E_{\text{fc}} = \frac{36 \times 5200 \times 0.64 \times 0.8}{2800} \approx 34.231

Symbol	Meaning	Unit
$E_{\text{fc}}$	maintained illuminance	fc
$N$	number of luminaires	—
$L$	initial lumens per luminaire	lm
$\mathrm{CU}$	utilization coefficient	—
$\mathrm{LLF}$	combined light-loss factor	—
$A$	work-plane area	ft²

Symbol	Meaning	Unit
$E_{\text{lux}}$	maintained illuminance	lux
$N$	number of luminaires	—
$L$	initial lumens per luminaire	lm
$\mathrm{CU}$	utilization coefficient	—
$\mathrm{LLF}$	combined light-loss factor	—
$A$	work-plane area	m²

Results are estimates for study and screening. Check the inputs, units and assumptions before you use them for design, billing or contract decisions.