What is UGR (Unified Glare Rating)?
UGR explained, the standard for measuring discomfort glare, target levels by space type, and why glare matters as much as lux.
Understanding Unified Glare Rating
UGR stands for Unified Glare Rating. It is an internationally recognised method of measuring discomfort glare from lighting systems.
Why Glare Matters
Poor lighting can create:
- Eye strain
- Headaches
- Reduced productivity
- Visual discomfort
Even if lux levels are correct. This is why professional lighting design considers glare alongside illumination.
UGR Scale
| UGR | Perception |
|---|---|
| Below 10 | Imperceptible |
| 10–16 | Comfortable |
| 16–19 | Acceptable |
| 19–22 | Noticeable |
| Above 22 | Uncomfortable |
Recommended UGR Levels
| Space | Target UGR |
|---|---|
| Offices | ≤ 19 |
| Schools | ≤ 19 |
| VDT-intensive workplaces | ≤ 16 |
| Premium hospitality lobbies | ≤ 16 |
| Residential | Flexible |
Factors Affecting UGR
- Fixture brightness
- Mounting position
- Beam angle
- Room reflectance
- Observer location
Common Mistakes
- Specifying lux without UGR
- Trusting marketing copy over IES files
- Ignoring observer position in DIALux
UGR is a calculation, not a measurement. Run it in DIALux from realistic observer positions, not from above.
Lighting Intelligence by Alya
At Ashwamedha Design Solutions, this is part of our Lighting Intelligence practice, every recommendation is validated through DIALux simulation, lux calculations and visual comfort analysis before it reaches a construction site. Alya, our lighting intelligence platform, packages this thinking into reusable design tools.
Frequently Asked Questions
Can I measure UGR on site?+
Not directly. It is calculated. On-site you can only check the proxy, glare complaints from users.
Does UGR apply to homes?+
Not strictly, but the underlying discomfort it represents applies anywhere. Avoid bright unshielded sources in sightlines.
Related Service
Commercial Lighting Design
See how this thinking is applied on live projects.
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Our team can review your space and turn these ideas into a measured lighting design.