Candela to Lux Calculator
Enter candela, distance, and the angle from the source axis. Lux depends on all three values, so this is an assumption-based estimate.
Illuminance: lx
Formula: E = I × cos(θ) ÷ d²
Estimate only; assumes a point source and forward-facing surface.
A QUICK WALKTHROUGH
How to use this tool
- Enter luminous intensity in candela (cd).
- Enter distance in metres and incidence angle from the source axis.
- Calculate illuminance using E = I × cos(θ) ÷ d².
Distance and angle are required
Candela measures intensity in a direction; lux measures illuminance on a surface. There is no direct unit-only conversion. This calculator assumes a point source, a perpendicular surface at the entered distance, and an angle measured from the source axis.
Formula
E = I × cos(θ) ÷ d², where E is illuminance in lux, I is candela, θ is the incidence angle from the axis, and d is distance in metres. Angles above 90° produce no forward illumination and are reported as 0 lx.
Planning estimate
The result does not model beam spread, optics, reflection, source size, occlusion, or inverse-square deviations at close range. It is not a photometric measurement or lighting-design guarantee.
GOOD TO KNOW
Common questions
Can candela be converted to lux directly?
No. Enter distance and surface angle because illuminance changes with both.
What does 0° mean?
The surface normal points along the source axis, so the cosine factor is 1.
Why is the result zero above 90°?
The surface faces away from the source, so this forward-facing model reports no illuminance.