Lux to Watts Conversion Calculator

This is an online calculator to convert lux to watts. Just enter the lux value and sphere radius then select the light source to get the corresponding watts value.

Enter the Lux Value and Sphere Radius then Select the Light Source to Calculate Lumens

  • lx
  • lm/W


  • Power in Watts
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Conversion Equation

Where 'r' is the radius of the sphere in feet.

In case, If you would like to use meters instead of feet, then convert sq. feet to sq. meter.

ie; 1 sq. mt. = 10.76391 sq. ft.

Luminous efficacy measures the efficiency of a light source in generating visible light.


Lux (lx) is the SI unit of illumination. It indicates the illumination intensity of an area.

One Lux is equal to One Lumen per square meter.

illuminance (Ev) is the amount of luminous flux per unit area.


Watt is a unit of Power. It is the amount of energy that a system requires to function. When electricity flows at a rate of one joule (unit of energy) per second, it is one watt.