UGR value explained: UGR 19, glare & office lighting
In short: The UGR value (Unified Glare Rating) assesses the psychological direct glare caused by luminaires in an indoor lighting system. The lower the UGR value, the lower the expected glare. For many typical office and screen-based tasks, a UGR limit of 19 is relevant. However, the specific room situation is always decisive—not just the luminaire alone.
What does UGR mean?
UGR stands for Unified Glare Rating, or in German, "unified glare rating". The method was developed by the CIE to assess disruptive direct glare in indoor spaces in a standardized way.
The UGR value does not simply describe how bright a luminaire is. It assesses how strongly luminaires are perceived as distractingly bright in relation to the surroundings from a specific observer position.
Is UGR a value of the luminaire or the room?
UGR is fundamentally a value of the lighting system in a specific room situation. A luminaire therefore cannot have a single UGR value regardless of the room.
Factors that have an influence include:
- Position and number of luminaires
- Observer's line of sight
- Room size and mounting height
- Luminance and size of visible light surfaces
- Brightness or reflectance of walls and ceiling
Manufacturers often provide UGR tables. These help lighting designers check whether a required limit can be met for defined room geometries and reflectance levels.
What does UGR 19 mean?
UGR 19 is a commonly used limit for classic office and screen-based tasks. In DIN EN 12464-1, different limits are specified for different activities to restrict psychological glare.
Important: The statement "UGR < 19" on a product alone is not a guarantee that a completed lighting system in every room will meet the limit of 19. The specific design must take into account the room, arrangement, and lines of sight.
What does UGR 16 mean?
A limit of UGR 16 places stricter requirements on glare reduction than UGR 19. Such lower limits may be relevant for particularly demanding visual tasks.
As a general rule: The lower the permissible UGR limit, the more the lighting system must be designed to minimize direct glare.
Is a lower UGR value always better?
For glare reduction, a lower UGR value is generally advantageous. However, it does not alone indicate whether a lighting system is well designed overall.
Other relevant factors include:
- sufficient illuminance
- uniform light distribution
- appropriate color temperature
- good color rendering
- suitable luminaire position
- reflected glare on screens and shiny surfaces
An extremely heavily shielded luminaire may cause little glare, but may still be unsuitable if the desired area is not sufficiently or uniformly illuminated as a result.
Which factors influence the UGR value?
Luminance of the luminaires
Very bright visible light surfaces can cause more glare than surfaces with lower luminance. The luminance in the direction of the observer is particularly relevant.
Position in the field of vision
A bright luminaire directly in the main line of sight is usually perceived as more disruptive than the same luminaire outside the central field of vision.
Size of the visible light source
The solid angle of the luminaire perceived by the eye also contributes to the UGR assessment.
Background brightness
The contrast between the luminaire and the surroundings plays a central role. A very bright luminaire against a dark background can cause more glare than the same luminaire in a well-balanced bright room.
UGR in offices and home offices
Glare reduction is particularly important in offices because employees work for long periods in relatively constant lines of sight. Luminaires should be designed so that they appear neither directly in the field of vision nor as disruptive reflections on monitors.
For many typical office tasks, the relevant UGR limit is 19. However, for compliant design, the specific activity and the requirements of the current DIN EN 12464-1 must always be taken into account. NOVADIS plans lighting, workstations, and acoustics together in the office planning.
THE Home Office – NOVARAIL lighting system for the workplace
UGR in medical practices and rooms
In medical practices and healthcare areas, several requirements often come together: good visual conditions, sufficiently high illuminance, low glare, and high color rendering.
Which UGR limit must be met depends on the respective room and the specific activity. Therefore, professional lighting design should not be based on a product specification alone.
THE Medical Pro – lighting system for medical applications
How can glare be reduced?
- Position luminaires outside critical lines of sight
- Use suitable optics, reflectors, and shields
- Avoid extremely high luminance in the direct field of vision
- Distribute light across several luminaires or larger areas
- Include walls and ceilings in the lighting design
- Consider screen position, luminaire position, and reflections together
Especially with track systems, the flexible positioning of luminaires is helpful because spotlights and other lighting modules can be aimed at the actual use of the room.
UGR and beam angle: What is the connection?
The beam angle influences where light is directed. It can therefore also influence whether a luminaire is perceived as disruptive from a specific line of sight.
However, a narrow beam angle does not automatically mean a low UGR value. The entire lighting system, including optics, position, luminance, and room geometry, is decisive.
Beam angle and light distribution explained
UGR, CRI, and Kelvin – three different values
| Value | What is described? |
|---|---|
| UGR | psychological direct glare from a lighting system |
| CRI / Ra | quality of color rendering |
| Kelvin | color temperature or light color |
All three values describe different aspects of light quality and should not be confused with one another.
CRI value and color rendering index explained
Color temperature in Kelvin explained
Why "UGR < 19" on the data sheet does not replace the complete design
A common misinterpretation is to automatically view a single luminaire with the designation "UGR < 19" as compliant office lighting.
However, the UGR method takes into account the entire system. Only from the luminaire, room, number, arrangement, mounting height, reflectance levels, and observer position does a reliable glare assessment emerge.
Professional office, medical practice, and commercial projects should therefore be designed using photometric data and suitable lighting design software.
Pre-plan the lighting system in the 3D configurator
The NOVARAIL 3D configurator helps with the spatial pre-planning of tracks, luminaires, and lighting zones. However, it does not replace a compliant UGR calculation.
Plan NOVARAIL in the 3D configurator
Frequently asked questions about the UGR value
What is a good UGR value?
It depends on the use. For many typical office and screen-based tasks, a limit of 19 is relevant. Other activities may have stricter or less strict requirements.
Is UGR 19 glare-free?
UGR 19 does not mean "completely glare-free". It is a specified limit for restricting psychological glare for certain applications.
Is UGR 16 better than UGR 19?
UGR 16 stands for a stricter glare reduction than UGR 19. Whether this stricter limit is required depends on the respective visual task.
Can a luminaire have a fixed UGR value?
Not independently of the room. Manufacturers can provide UGR tables for standardized room situations. However, the actual value of a lighting system depends on the specific design.
What is the difference between UGR and reflected glare?
UGR mainly assesses psychological direct glare from luminaires. Disruptive reflections on monitors or shiny surfaces are an additional design topic and are not fully described by a single UGR value.
How is UGR calculated?
The UGR method takes into account, among other things, the luminance of the glare sources, their visible solid angle, their position in the field of vision, and the background brightness. In practice, UGR tables or lighting design software are used for this.
Which standard is relevant for UGR at the workplace?
For the lighting of workplaces in indoor spaces, DIN EN 12464-1 is particularly relevant in Germany. The currently published version is DIN EN 12464-1:2021-11.
Conclusion
The UGR value is an important value for restricting disruptive direct glare in indoor spaces. UGR 19 is a central design value for many office applications, but not a blanket quality label for a single luminaire.
Good lighting design considers UGR together with illuminance, light distribution, screen reflections, color temperature, and color rendering.
Sources and further fundamentals
- DIN EN 12464-1:2021-11 – Light and lighting – Lighting of workplaces – Part 1: Workplaces in indoor spaces
- CIE 117:1995 – Discomfort Glare in Interior Lighting
- CIE 190:2010 – Calculation and Presentation of Unified Glare Rating Tables for Indoor Lighting Luminaires
- CIE 232:2019 – Discomfort Caused by Glare from Luminaires with a Non-Uniform Source Luminance
