Beam angle is the angular spread of a light beam, measured between points where luminous intensity falls to 50% of its maximum value.
Beam angle defines how widely a light source distributes illumination, measured in degrees at the base of the light cone where brightness is half that of the center. Narrower angles, typically 15°–25°, concentrate light in a tight spot for accenting or long-distance projection, while wider angles, often 60°–120°, deliver broader coverage suitable for general illumination. In commercial AV, access control, and architectural lighting, beam angle ensures fixtures meet functional requirements such as uniform brightness, display visibility, or camera performance.
Beam angle definitions and testing are guided by the Illuminating Engineering Society (IES) and the International Commission on Illumination (CIE).
The concept of beam angle gained traction with the rise of directional luminaires. As lighting technology evolved, it became a standard specification in commercial design, ensuring accurate comparisons of fixture performance.