This luminous flux calculator finds the total luminous flux in lumens from a source’s intensity in candela and its beam cone angle. Enter both values above.
Formula
Φ = Iv × 2π × (1 − cos(θ))
- Iv — intensity (cd), θ — cone half-angle
Example
100 cd, 30° half-angle: Φ = 100 × 2π × (1 − cos30°) = 84.2 lm.
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Frequently Asked Questions
How do I convert candela to lumens?
Multiply intensity by the solid angle of the beam: lumens = candela x 2pi x (1 – cos of the half-angle).
What is luminous flux?
It is the total visible light a source emits, measured in lumens, unlike candela which is intensity in one direction.
Does a narrower beam give fewer lumens?
For the same candela, yes. A narrower cone spans a smaller solid angle, so fewer total lumens.