What is UGR (Unified Glare Rating)?

How is UGR Measured?

UGR is calculated using a formula defined in CIE 117 that considers the luminance of the luminaire, the background luminance of the room, the solid angle of the luminaire as seen by the observer, and the position index (viewing angle). It is not a property of a single luminaire — it depends on the entire room geometry, surface reflectances and luminaire layout.

However, luminaire manufacturers publish 'UGR tabular values' based on standardised room dimensions and reflectances (SHR tables), allowing specifiers to estimate the UGR contribution of a specific fitting before performing a full lighting calculation.

UGR Limits in UK Standards

BS EN 12464-1 specifies maximum UGR values for different task areas:

• General offices, classrooms — UGR ≤ 19 • Drawing offices, CAD workstations — UGR ≤ 16 • Corridors, stairways — UGR ≤ 25 • Industrial assembly (fine work) — UGR ≤ 16 • Hospital wards — UGR ≤ 19 • Retail — UGR ≤ 22

A UGR of 19 is the most commonly specified limit in UK commercial interiors. Luminaires with UGR < 19 are considered 'low glare' and are essential for display screen equipment (DSE) compliance under the Health and Safety (Display Screen Equipment) Regulations 1992.

How EOS Achieves Low UGR

EOS luminaires achieve low UGR through precision optical design:

• Micro-prismatic diffusers — break up direct LED brightness into uniform, diffused light • Recessed optics — LED arrays are set back within the luminaire housing to reduce high-angle brightness • Louvred optics — aluminium louvres cut off light above 60° to eliminate direct glare from typical viewing positions • Dark-light reflector technology — specular reflectors direct light downward while presenting a dark appearance from high angles

Our product datasheets include full UGR tables so specifiers can verify compliance before ordering.