ClueLuma

Luminous efficacy calculator

Measures lamp light output per watt under specified test conditions.

Efficacy=LumensInput watts\text{Efficacy} = \frac{\text{Lumens}}{\text{Input watts}}

Calculator

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

W
lm
lm/W

Worked example

Given

  • Input watts\text{Input watts} = 30 W
  • Lumens\text{Lumens} = 3,600 lm
Efficacy=360030=120\text{Efficacy} = \frac{3600}{30} = 120

Symbols and units

SymbolMeaningUnit
Efficacy\text{Efficacy}light per electric powerlm/W
Input watts\text{Input watts}electric inputW
Lumens\text{Lumens}light outputlm

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