What Is UGR?
Definition, standards, typical values, applications and the procurement checks for UGR.
🕒 Updated 2026-09-17 · 🧾 Verified by the CompareDeals lighting team
Definition
UGR sits on the short list of parameters that buyers, designers and factories interpret differently.
UGR is a design or procurement concept that decides how a project moves from a requirement to an executable specification.
Concepts cannot be reduced to one number, but they surface after installation as comfort, energy or maintenance frequency.
How Does It Work — UGR
Making a concept real needs three things: a performance goal, a measurable criterion, and hardware specifications that agree with it.
Without the criterion, each party reads the same result differently and handover stalls.
The reliable route is to translate the concept into four measurable terms: illuminance, uniformity, colour temperature and glare limits.
Key Data: Specifications & Standards
UGR is calculated from the whole room, not the luminaire: the same fixture can pass in a 3 m office and fail in a 2.6 m one
| Parameter | Value / level | Explanation |
|---|---|---|
| UGR < 16 | Very low glare | Drafting, CAD, control rooms, classrooms |
| UGR < 19 | Low glare | Standard offices, meeting rooms, libraries |
| UGR < 22 | Moderate | Circulation, industrial support areas |
| UGR < 25 | Industrial | Warehouse and factory where tasks are not visual |
| UGR < 28 | Rough service | High mast, exterior, non-task areas |
Reference standard: CIE 117 / EN 12464-1
Applications: Where It Fits
UGR appears in the design document, the purchase order and the acceptance test; all three must quote the same figure with the same condition.
When the three documents disagree, the usual outcome is a compliant fixture inside a project that fails inspection.
Comparison to Alternatives
| Criterion | Concept only | Measurable specification | Contractual KPI |
|---|---|---|---|
| Definition | A design intention | A number with a condition | A number with a penalty |
| Verification | Opinion at handover | Measurement at commissioning | Measurement plus audit |
| Dispute risk | High | Medium | Low |
| Cost impact | Unknown | Designed in | Priced in |
Common Pitfalls and Specification Rules
Translate the concept into measurable acceptance clauses.
Copying a UGR value from a datasheet without the room geometry is the most common specification error in offices.
- Run a mock-up at the sample stage on the real surface and ceiling.
- Agree in advance how a deviation will be handled: rework, adjust or accept.
Conclusion & Procurement Recommendation
For screen-based work target UGR ≤ 19 with a luminance ceiling of 3,000 cd/m² at 65° and above.
The cheapest compliant bid and the cheapest non-compliant bid usually look identical on a quotation sheet.
🔑 Key Takeaways
- UGR is only meaningful together with its test condition.
- Put the value, the standard and the tolerance into the purchase order and the quality agreement.
- Sample-test the first shipment at a third party: it costs far less than rework.
- Keep one emitter bin and one driver platform across the whole project.
Frequently Asked Questions
What is a normal compliant value for UGR?
For screen-based work target UGR ≤ 19 with a luminance ceiling of 3,000 cd/m² at 65° and above. Most commercial projects sit in the standard tier; only a stated requirement justifies moving up.
How can I verify the figure a supplier quotes?
Ask for the report against CIE 117 / EN 12464-1 and check that the model on the report matches the model being shipped.
How much does UGR vary between batches?
Batch consistency depends on keeping one emitter bin and one driver platform. Change either and you must re-sample.
How should this be written into the purchase order?
Value + standard + test condition + tolerance band. Miss any one of the four and the supplier has room to interpret.
What if the project is already under construction?
Test on site, quantify the deviation, then decide between rework, adjustment or acceptance and record the decision.
📋 Sources & Verification
| Manufacturer datasheet | Nominal values and installation conditions |
|---|---|
| CIE 117 / EN 12464-1 | Test method and pass criteria |
| Third-party laboratory report | Measured performance and deviation |
| Platform verification record | Certificate number cross-checked with the issuer |
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