UGR – Unified Glare Rating Explained
What is UGR and why does it matter?
UGR (Unified Glare Rating) is a measure of discomfort glare in indoor spaces. It is not a property of a luminaire, but a result of the entire lighting installation — including room geometry, surface reflectance, luminaire placement, and the observer’s position. The luminaire’s brightness is only one part of the equation.
Choosing the right luminaire is still essential to meeting UGR requirements, especially in industrial spaces where powerful luminaires are needed. For example, solutions like I-Valo’s XENRE use advanced reflector technology to deliver high light output while keeping glare low — something standard diffuser-based luminaires often struggle with.
Perceived glare also depends on the contrast between the light source and its surroundings. A good example is car headlights: they are equally bright during the day and at night, but they seem much more glaring in darkness because the background is dimmer.
These three images of the same car with its headlights on — captured in daylight, at dusk, and at night — demonstrate how ambient light levels influence the way we perceive glare.
Because UGR is context-dependent, the best way to ensure visual comfort is to simulate and verify the lighting design. Our experts at I-Valo can help — using professional software, photometric data, and real-world experience — to create lighting solutions with the right balance of illumination and glare control for your environment.
Better lighting starts with UGR
Interested in learning more? Click below to download our in-depth white paper.
We would be happy to answer any of your questions. Alternatively we can set up a meeting with you, enabling us to understand all of your needs.
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