Lux to Lumens Calculator
Enter illuminance in lux and the illuminated area. The result assumes uniform illuminance across that area.
Luminous flux: lm
Formula: Φ = E × A
Estimate only; assumes uniform illuminance across the entered area.
A QUICK WALKTHROUGH
How to use this tool
- Enter illuminance in lux (lx).
- Enter the illuminated area in square metres.
- Calculate estimated luminous flux in lumens (lm) using Φ = E × A.
Area is required
Lux measures illuminance on a surface, while lumens measure total luminous flux. A lux-to-lumens estimate requires the illuminated area.
Uniform-illuminance assumption
This calculator assumes the entered illuminance is uniform across the entire entered area. It does not model beam spread, optics, distance, reflection, occlusion, or fixture losses.
Formula
Φ = E × A, where Φ is luminous flux in lumens, E is illuminance in lux, and A is illuminated area in square metres.
GOOD TO KNOW
Common questions
Can lux be converted to lumens directly?
No. Enter the illuminated area; the tool then uses lm = lx × m² under the stated uniform-illuminance assumption.
Does this predict a fixture output or measured room illuminance?
No. It is a planning estimate and does not account for fixture, room, or light-distribution conditions.