Luminous Efficacy

Calculate luminous efficacy and power requirements for various light sources. Luminous efficacy is the ratio of luminous flux (lumens) to power (watts), determining how efficiently a light source produces visible light.

Luminous Efficacy Calculator

Luminous Efficacy (η) is the ratio of luminous flux to power:

η = Φ / P

Where:

  • η = Luminous efficacy (lumens/W)
  • Φ = Luminous flux (lumens, lm)
  • P = Power (W)

You can also calculate required power: P = Φ / η

Calculator

Inputs

Results

Required Power-- W
Light TypeLuminous Efficacy Range (lumens/W)
Fluorescent lamp45 - 75
Halogen lamp16 - 24
High pressure sodium vapor lamp85 - 150
LED lamp30 - 90
Mercury vapor lamp35 - 65
Metal halide lamp75 - 100
Tungsten incandescent light bulb lamp12 - 18