Required lumen-method fixture count calculator

Calculated fixture count is calculated as E × A / (L × CU × LLF). Use the stated system boundary and matching input units.

Units

N = \frac{E \times A}{L \times \mathrm{CU} \times \mathrm{LLF}}

Calculator

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

Given

N = \frac{50 \times 2400}{5000 \times 0.65 \times 0.75} \approx 49.231

Symbol	Meaning	Unit
$N$	calculated fixture count	fixture
$E$	maintained target illuminance	fc
$A$	task-plane area	ft²
$L$	initial lumens per fixture	lm
$\mathrm{CU}$	coefficient of utilization	—
$\mathrm{LLF}$	light-loss factor	—

Symbol	Meaning	Unit
$N$	calculated fixture count	fixture
$E$	maintained target illuminance	lux
$A$	task-plane area	m²
$L$	initial lumens per fixture	lm
$\mathrm{CU}$	coefficient of utilization	—
$\mathrm{LLF}$	light-loss factor	—

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