ClueLuma

Coefficient of utilization (CU) calculator

CU connects lamp output with light reaching the working surface.

CU=Lumens on work planeLamp lumens\mathrm{CU} = \frac{\text{Lumens on work plane}}{\text{Lamp lumens}}

Calculator

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

lm
lm
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Worked example

Given

  • Lumens on work plane\text{Lumens on work plane} = 2,400 lm
  • Lamp lumens\text{Lamp lumens} = 4,000 lm
CU=24004000=0.6\mathrm{CU} = \frac{2400}{4000} = 0.6

Symbols and units

SymbolMeaningUnit
CU\mathrm{CU}fraction reaching the working surface—
Lumens on work plane\text{Lumens on work plane}useful work-plane lightlm
Lamp lumens\text{Lamp lumens}lamp 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.