Conversion Equation

Where 'θ' is the apex angle in degrees.

Candela

Candela (cd) is the SI unit of Luminous Intensity. It indicates the strength of light emission and is defined as the luminous power per unit solid angle emitted by a light source in a particular direction.

Unit Solid Angle means the solid angle of a sphere subtended by a portion of the surface whose area is equal to the square of the sphere's radius.

Luminous Intensity (Iv) of a light source is the emitted luminous power or luminous flux per unit solid angle.

Lumen

Lumen is the SI unit of Luminous Flux. It indicates the total amount of visible light emitted from a source.

Luminous Flux / Luminous Power is the amount of light energy radiated from a source in all directions per second and is denoted as F.

Apex Angle

An Apex is the tip of a cone. The Apex Angle ( θ ) is the intersection of the lines defining the apex, as shown in the figure.