Luminous Intensity Converter

Convert between candela, lumen, and lux with explicit geometry assumptions. The form asks for Value, From unit, To unit, Distance in meters, and Emission solid angle in steradians. It returns the selected conversion and a list of all three supported light units.

How to use this calculator

Choose candela, lumen, or lux as the starting unit, then select the target unit. Keep the default solid angle for a full-sphere approximation, or enter a beam solid angle from measured or manufacturer data. Distance matters whenever lux is involved. For electrical power comparisons, use the power converter; for sound intensity style logarithms, see the decibel calculator.

How it works

Candela is the base unit in the form’s calculations. Lumens depend on solid angle, and lux depends on distance:

$candela = lumens \div solid\ angle$

$candela = lux \times distance^2$

$lumens = candela \times solid\ angle$

$lux = candela \div distance^2$

Worked example

Convert 500 lumens to candela using the default full sphere, about 12.566 sr:

$500 \div 12.566 = 39.79$

The calculator reports about 39.79 cd. If you then convert 39.79 cd to lux at 2 meters:

$39.79 \div 2^2 = 9.95$

So the illuminance is about 9.95 lx.

Unit guide

For general SI scaling alongside lighting calculations, the length converter can help keep distance inputs consistent.