# Lumens to lux calculator

Luminous flux in lumens (lm) to illuminance in lux (lx) calculator and how to calculate.

Enter the luminous flux in lumens, select area unit type, enter radius in meters for spherical light source or surface area

in square meters for any light source and press the *Calculate* button to get the illuminance in lux:

## Lumens to lux calculation formula

### Calculation with area in square feet

The illuminance *E*_{v} in lux (lx) is equal to 10.76391 times the luminous flux *Î¦*_{V}
in lumens (lm) divided by the surface area *A* in square feet (ft^{2}):

*E*_{v(lx)} = 10.76391 Ã—* Î¦*_{V(lm)} / *A*_{(ft}2_{)}

For a spherical light source, the area A is equal to 4 times pi times the squared sphere radius:

* A* = 4â‹…Ï€â‹…*r *^{2}

The illuminance *E*_{v} in lux (lx) is equal to 10.76391 times the luminous flux *Î¦*_{V}
in lumens (lm) divided by 4 times pi times the squared sphere radius r in feet (ft):

*E*_{v(lx)} = 10.76391 Ã—* Î¦*_{V(lm)}* *
/* *(4â‹…Ï€â‹…*r*_{(ft)}^{2})

So

lux = 10.76391 Ã—* *lumens / (square feet)

or

lx = 10.76391 Ã—* *lm / ft^{2}

### Calculation with area in square meters

The illuminance *E*_{v} in lux (lx) is equal to the luminous flux *Î¦*_{V}
in lumens (lm) divided by the surface area *A* in square meters (m^{2}):

*E*_{v(lx)} = *Î¦*_{V(lm)}* *
/* A*_{(m}2_{)}

For a spherical light source, the area A is equal to 4 times pi times the squared sphere radius:

* A* = 4â‹…Ï€â‹…*r *^{2}

So the illuminance *E*_{v} in lux (lx) is equal to the luminous flux *Î¦*_{V} in lumens (lm) divided by 4 times pi times the squared sphere radius
r in meters (m):

*E*_{v(lx)} = *Î¦*_{V(lm)} /* *(4â‹…Ï€â‹…*r*_{(m)}* *^{2})

So

lux = lumens / (square meters)

or

lx = lm / m^{2}

##### Example

What is the luminous flux on a surface of 4 square meters and illuminance of 500 lux?

*Î¦*_{V(lm)} = 500 lux Ã— 4 m^{2} = 2000 lm