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Watts to lumens calculator

Electric power in watts (W) to luminous flux in lumens (lm) calculator and how to calculate.

Enter the power in watts, luminous efficacy in lumens per watt and press the Calculate button to get the luminous flux in lumens:

Enter power in watts: W
Enter light source:
Or enter luminous efficacy in lumens per watt: lm/W
Luminous flux result in lumens: lm

* the predefined luminous efficacy values are typical / average values.


Watts to lumens calculation formula

The luminous flux ΦV in lumens (lm) is equal to the power P in watts (W), times the luminous efficacy η in lumens per watt (lm/W):

ΦV(lm) = P(W) × η(lm/W)


lumens = watts × (lumens per watt)


lm = W × (lm/W)


What is the luminous flux of a lamp that has power consumption of 60 watts and luminous efficacy of 15 lumens per watt?

ΦV = 60 W × 15 lm/W = 900 lm

Luminous efficacy table

Light type Typical
luminous efficacy
Tungsten incandescent light bulb 12.5-17.5 lm/W
Halogen lamp 16-24 lm/W
Fluorescent lamp 45-75 lm/W
LED lamp 80-100 lm/W
Metal halide lamp 75-100 lm/W
High pressure sodium vapor lamp 85-150 lm/W
Low pressure sodium vapor lamp 100-200 lm/W
Mercury vapor lamp 35-65 lm/W

Energy saving lamps have high luminous efficacy (more lumens per watt).