This lumens to watts calculator estimates the power required to achieve your chosen lumen level.

Enter the lumens, then either choose the most appropriate light source from the list or enter the lumens per watt of your light source, to get the power in watts result.

Use calculate button if answer isn't shown automatically

Lumens to Watts Conversion Formula

The conversion of lumens to watts uses the formula:

Watts = Lumens / Efficiency (lumens per watt)

For example, an LED with an efficiency of 75 lumens per watt would require 5.41 watts to produce 460 lumens.

460 lumens / 85 lumens per watt = 5.41 watts

Understanding Lumens vs Watts

As lumens measure the amount of light and watts the amount of power used to create that light, the only accurate way to calculate the power consumption in Watts, is to know how efficient the light source is.

This efficiency is described as the efficacy, the measurement of how efficiently a light source produces visible light.

Lm/W Efficacy

The Lm/W efficacy is measured in lumens per watt (lm/W) or light output per watt.

A higher efficacy means more light for the same amount of power, with different light types and even different models within a light type varying quite a bit.

For reference, here are some average lm/W efficacies for various light types:

Compact Fluorescent Lights (CFLs): 60-90 lm/W

Tungsten Incandescent Lights: 12 lm/W

LED Lights: 50 lm to 250 lm/W (varies widely by LED)