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Luminous Efficacy Calculator

Lumens per watt of a lamp, with how it compares to other lighting technologies.

Also known as lumens per watt, lamp efficiency calculator, lighting efficacy.

Enter values

Results update as you type.

Result

Luminous efficacy

88.89 lm/W

Technology match
Standard LED
Energy rating band
F
Watts for 1000 lumens
11.25
Compared to incandescent (14 lm/W)
6.35 ×

About the Luminous Efficacy Calculator

Lumens per watt of a lamp, with how it compares to other lighting technologies.

Also known as: lumens per watt, lamp efficiency calculator, lighting efficacy, bulb efficiency.

How to use this calculator

  1. Enter light output, power consumption.
  2. The result updates instantly as you type — press Calculate (or Enter) at any time.
  3. Review the breakdown shown under the main result.
  4. Use Copy result or Share to save the answer or send a link with your inputs.

Luminous Efficacy formula

efficacy = lumens ÷ watts

Worked example

Using the values pre-filled in the calculator above:

  • Light output = 800 lm
  • Power consumption = 9 W

the calculator returns:

  • Luminous efficacy: 88.89 lm/W
  • Technology match: Standard LED
  • Energy rating band: F
  • Watts for 1000 lumens: 11.25