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.
The illuminance Ev in lux (lx) is equal to 10.76391 times the luminous flux ΦV in lumens (lm) divided by the surface area A in square feet (ft2):
Ev(lx) = 10.76391 × ΦV(lm) / A(ft2)
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 Ev in lux (lx) is equal to 10.76391 times the luminous flux ΦV in lumens (lm) divided by 4 times pi times the squared sphere radius r in feet (ft):
Ev(lx) = 10.76391 × ΦV(lm) / (4⋅π⋅r(ft)2)
So
lux = 10.76391 × lumens / (square feet)
or
lx = 10.76391 × lm / ft2
The illuminance Ev in lux (lx) is equal to the luminous flux ΦV in lumens (lm) divided by the surface area A in square meters (m2):
Ev(lx) = ΦV(lm) / A(m2)
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 Ev in lux (lx) is equal to the luminous flux ΦV in lumens (lm) divided by 4 times pi times the squared sphere radius r in meters (m):
Ev(lx) = ΦV(lm) / (4⋅π⋅r(m) 2)
So
lux = lumens / (square meters)
or
lx = lm / m2
What is the luminous flux on a surface of 4 square meters and illuminance of 500 lux?
ΦV(lm) = 500 lux × 4 m2 = 2000 lm
