## How to convert lumens to lux

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

You can calculate lux from lumens and surface area.

Lux and lumen units represent different quantities, so you can't convert lumens to lux.

- Lumens to lux calculation with area in square feet
- Lumens to lux calculation with area in square meters
## Lumens to lux calculation formula

## Lumens to lux calculation with area in square feet

The illuminance

E_{v}in lux (lx) is equal to 10.76391 times the luminous fluxΦ_{V}in lumens (lm) divided by the surface areaAin square feet (ft^{2}):

E_{v(lx)}= 10.76391 ×Φ_{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= 4·π·r^{2}

So the illuminance

E_{v}in lux (lx) is equal to 10.76391 times the luminous fluxΦ_{V}in lumens (lm) divided by 4 times pi times the squared sphere radius r in feet (ft):

E_{v(lx)}= 10.76391 ×Φ_{V(lm)}/(4·π·r_{(ft)}^{2})

So

lux = 10.76391 ×

lumens / (square feet)or

lx = 10.76391 ×

lm / ft^{2}## Lumens to lux calculation with area in square meters

The illuminance

E_{v}in lux (lx) is equal to the luminous fluxΦ_{V}in lumens (lm) divided by the surface areaAin square meters (m^{2}):

E_{v(lx)}=Φ_{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= 4·π·r^{2}

So the illuminance

E_{v}in lux (lx) is equal to the luminous fluxΦ_{V}in lumens (lm) divided by 4 times pi times the squared sphere radius r in meters (m):

E_{v(lx)}=Φ_{V(lm)}/(4·π·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?

Φ_{V(lm)}= 500lux × 4m^{2}= 2000 lm

## See also