# Lux to watts convert calculator with formulas

Illuminance in lux (lx) to electric power in watts (W) calculator and how to calculate.

Enter the illuminance in lux, luminous efficacy in lumens per watt, surface area in square feet / meters or spherical radius in feet / meters and press the Calculate button to get the power in watts:

 Enter illuminance in lux: lx Select light source: -- select light source -- Tungsten incandescent light bulb Halogen lamp Fluorescent lamp LED lamp Metal halide lamp High pressure sodium vapor lamp Low pressure sodium vapor lamp Mercury vapor lamp Or enter luminous efficacy in lumens per watt: lm/W Enter surface area: ft² m² Or enter spherical radius: ft m Power  result in watts: W

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

## Lux to watts calculation formula and use

#### Lux to watts calculation with area in square feet

The power P in watts (W) is equal to the 0.09290304 times the illuminance Ev in lux (lx) times the surface area A in square feet (ft2), divided by the luminous efficacy η in lumens per watt (lm/W):

P(W) = 0.09290304 × Ev(lx) × A(ft2) / η(lm/W)

#### Lux to watts calculation with area in square meters

The power P in watts (W) is equal to the illuminance Ev in lux (lx) times the surface area A in square meters (m2), divided by the luminous efficacy η in lumens per watt (lm/W):

P(W) = Ev(lx) × A(m2) / η(lm/W)

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