UGR (Unified Glare Rating)

UGR is a standardized numerical metric assessing the level of discomfort glare experienced by an observer in a room lit by a given system of luminaires.

How is UGR calculated?

The UGR metric accounts for the brightness (luminance) of every luminaire visible in the observer's field of view, its angular size, its position relative to the line of sight, and the background brightness of the room. Simulation lets you calculate UGR for a specific luminaire layout and room geometry before installation.

Applications

UGR is a required design parameter in interior lighting standards for offices and industrial spaces (e.g. EN 12464-1), where a typical requirement is a UGR below 19 for workstations with a computer monitor.

Related terms

Irradiance

Monte Carlo method in optics

Stray light