How to convert illuminance in lux (lx) to luminous flux in lumens (lm).

You can calculate lumens from lux and surface area. Lux and lumen units represent different quantities, so you can't convert lux to lumens.

- Lux to lumens calculation with area in square feet
- Lux to lumens calculation with area in square meters

## Lux to lumens calculation formula

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

The luminous flux *Φ*_{V} in lumens (lm) is equal to 0.09290304 times the illuminance *E*_{v} in lux (lx) times the surface area *A* in square feet (ft^{2}):

*Φ*_{V(lm)} = 0.09290304* *×* E*_{v(lx)}* *×* A*_{(ft}2_{)}

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

* A* = 4⋅π⋅*r *^{2}

So the luminous flux *Φ*_{V} in lumens (lm) is equal to 0.09290304 times the illuminance *E*_{v} in lux (lx) times 4 times pi times the squared sphere radius r in feet (ft):

*Φ*_{V(lm)} = 0.09290304* *×* E*_{v(lx)}* *×* *4⋅π⋅*r*_{(ft)}* *^{2}

So

lumens = 0.09290304* *×* *lux × (square feet)

or

lm = 0.09290304* *×* *lx × ft^{2}

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

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

*Φ*_{V(lm)} = *E*_{v(lx)}* *×* A*_{(m}2_{)}

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

* A* = 4⋅π⋅*r *^{2}

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

*Φ*_{V(lm)} = *E*_{v(lx)}* *× 4⋅π⋅*r *^{2}

So

lumens = lux × (square meters)

or

lm = lx × m^{2}

##### Example

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

*Φ*_{V(lm)} = 500 lux × 4 m^{2} = 2000 lm

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