How to convert lumens to watts

How to convert luminous flux in lumens (lm) to electric power in watts (W).

You can calculate watts from lumens and luminous efficacy.  Lumen and watt units represent different quantities, so you can't convert lumens to watts.

Lumens to watts calculation formula

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

P_(W) = ϕ_V(lm) / η_(lm/W)

So

watts = lumens / (lumens per watt)

or

W = lm / (lm/W)

Example

What is the power consumption of a lamp that has luminous flux of 900 lumens and luminous efficacy of 15 lumens per watt?

P = 900lm/W / 15lm/W = 60W

Luminous efficacy table

Light type	Typical luminous efficacy (lumens/watt)
Tungsten incandescent light bulb	12.5-17.5 lm/W
Halogen lamp	16-24 lm/W
Fluorescent lamp	45-75 lm/W
LED lamp	30-90 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

 

How to convert watts to lumens ►

 

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See also

• Lumens to watts calculator
• How to convert watts to lumens
• Lumens to lux calculation
• Lux to lumens calculation
• Watts (W)
• Electrical calculation
• Power conversion
• Energy conversion