Combined light-loss factor (LLF) calculator

Combined light-loss factor is calculated as LLD × LDD. Use the stated system boundary and matching input units.

\mathrm{LLF} = \mathrm{LLD} \times \mathrm{LDD}

Calculator

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

Given

\mathrm{LLF} = 0.9 \times 0.85 = 0.765

Symbol	Meaning	Unit
$\mathrm{LLF}$	combined light-loss factor	—
$\mathrm{LLD}$	lamp lumen depreciation	—
$\mathrm{LDD}$	luminaire dirt depreciation	—

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