Beam angle describes how widely a light spreads from a fitting.
Beam angle is the spread of light from a fitting, measured in degrees.
Technical meaning
Beam angle is the nominal angular spread of a luminaire beam, usually read as a cone angle in degrees.
For simple geometry, the beam is treated as symmetrical and the half-angle is used with effective height to estimate footprint diameter.
Calculation use
Beam diameter is calculated as 2 x effective height x tan(beam angle / 2).
The result helps compare narrow, medium and wide beams before checking spacing, overlap and the assessed plane.
Not the same as
Beam angle is not lumen output. A narrow and wide beam can have the same lumens but different footprint intensity.
Beam angle is not a lux, glare or uniformity result. It only describes geometric spread for the selected mounting height and plane.
Australian context
Australian room, retail and outdoor notes should record beam angle beside mounting height, workplane height and luminaire output so the geometry can be checked later.
Examples
Example
Value
Planning note
Narrow accent beam
24 degree
Small footprint for highlighting a surface or object.
General downlight beam
60 degree
Common geometry input for room and downlight-spacing estimates.
Wide flood beam
90 degree
Large footprint; still needs spill, glare and maintained-light checks.