UGR, of Unified Glare Rating, is an international standard that indicates the extent to which a lighting installation causes glare for people in a room. The lower the UGR value, the less glaring the lighting. This is directly relevant for workplace lighting: glare reduces concentration, increases the likelihood of errors, and poses a serious safety risk in industrial environments. The questions below elaborate on each aspect of UGR in a practical way — from calculation to luminaire selection.
How is the UGR value calculated?
The calculation takes into account the luminance of the light sources, the background illuminance, the position of the viewer, and the angle at which the luminaires are viewed. The result is a number on a logarithmic scale, typically between 10 and 30. The higher the number, the greater the perceived glare.
The formula has been standardized by the CIE (Commission Internationale de l’Eclairage) and is applied internationally. In practice, lighting designers perform the UGR calculation using specialized software such as DIALux or Relux, where the exact light emission of each luminaire is entered via a photometric data file (LDT or IES).
Important to understand: the UGR value is not a property of a single luminaire in itself. It is always a result of the entire lighting installation in a specific room, with a certain arrangement, ceiling and wall reflections, and a fixed viewing position. A luminaire can have a UGR of 19 in one room and a UGR of 22 in another room.
What do the different UGR limit values mean in practice?
The scale runs in steps of 3: UGR 10, 13, 16, 19, 22, 25, and 28. Limit values indicate how much glare is acceptable for a specific task or workplace. In practice, values of 19 and 22 are most commonly used, depending on the visual demands of the work.
- UGR < 10 Virtually no glare. Rarely required in standard work environments.
- UGR < 13 Very high visual demands, for example in precision assembly or medical environments.
- UGR < 16: Drawing tables, fine craftsmanship, and technical drawing.
- UGR < 19: Office workspaces with screens, inspection tasks, machine operation.
- UGR < 22 Industrial production spaces, warehouses, and workshops with less precise visual tasks.
- UGR < 25 Heavy industrial environments, storage areas, and spaces without fine visual work.
- UGR < 28 Hallways, stairwells, and spaces with low visual demands.
For operators who operate machines or perform quality control, UGR < 19 is the minimum requirement in most cases. For display screen work, this has even become a hard standard in European guidelines.
The standards that stipulate UGR requirements in the workplace are: * **NEN-EN 12464-1:** Lighting - Workplaces - Part 1: Indoor workplaces * **ISO 8995-1:** Lighting and marking of work places - Part 1: Indoor work places (This is the international equivalent of EN 12464-1)
The main standard that establishes UGR requirements for workplace lighting is NEN-EN 12464-1. This European standard describes the lighting requirements for indoor spaces, including minimum illuminances, color rendering, and maximum UGR limits per type of workplace or activity.
In addition EN 12464-2 for outdoor workplaces, such as Terminals, construction sites, and industrial areas. For specific sectors, additional requirements may apply based on industry guidelines, the Dutch Working Conditions Act (Arbowet), or clients. In the offshore and heavy industry, stricter requirements are sometimes imposed than the basic standard prescribes.
The Dutch Working Conditions Act obliges employers in the Netherlands to ensure a safe and healthy working environment. Glare from lighting falls under this. NEN-EN 12464-1 is considered a recognized practical guideline for meeting that obligation. Lighting expert can assess whether an existing installation complies with applicable standards.
What is the difference between UGR and glare rating (GR)?
UGR (Unified Glare Rating) and GR (Glare Rating) both measure glare but are applied in different situations. UGR is intended for indoor spaces and measures psychological glare: the uncomfortable sensation that disrupts concentration and visual comfort. GR was developed for outdoor lighting and measures physiological glare: the actual limitation of vision due to direct light in the field of view.
In practice, this means the following distinction:
- UGR is used in lighting designs for production areas, offices, workshops, and other indoor workplaces. The standard is NEN-EN 12464-1.
- Greece is used in outdoor lighting such as landscape lighting, sports fields and harbor facilities. The standard is EN 12464-2.
A fixture with a good UGR value for indoor use will not automatically perform well on GR for outdoor applications. When selecting fixtures for mixed environments—such as covered loading docks or industrial halls with exterior doors—it is important to assess both values.
How to choose a luminaire with the correct UGR value?
You start by determining the visual requirements of the work in the space. First, determine which UGR limit value applies according to NEN-EN 12464-1, and then look at luminaires that can achieve that value in a representative arrangement.
Follow these steps:
- Determine the task class: What activities take place? Fine manual work, machine operation, warehouse work? This determines the required UGR limit value.
- Check the light beam and shielding: Fixtures with a wider light beam or less shielding produce more glare. Choose fixtures with directed optics or diffuse shielding for visually sensitive environments.
- Request photometric data: Reliable manufacturers provide LDT or IES files that allow a lighting designer to perform an accurate UGR calculation.
- Perform a lighting calculation. Use software such as DIALux to simulate the UGR value in the specific room before installation.
- Take into account mounting height and position: The same luminaire at a different height or position yields a different UGR result. Optimize the layout in the simulation.
For LED work lights Different considerations apply to the operating machines of cranes than to ceiling lighting in a production hall. In those cases, non-glare optics and targeted beams are even more important, as operators and bystanders can have the light source directly in their field of vision.
When is a UGR calculation insufficient and what then?
A UGR calculation provides a good indication of glare risks, but falls short in situations with complex geometries, highly reflective surfaces, dynamic lighting, or unusual viewing positions. In those cases, additional analysis or a practical measurement is needed to assess the actual glare experience.
Situations where a standard UGR calculation is insufficient:
- Spaces with shiny floors, machines or products that reflect light into the eyes of operators.
- Environments with both artificial light and strong incident daylight, where the contrast ratio fluctuates significantly.
- Workspaces where people move and view lighting from multiple angles, such as in crane cabins or on moving vehicles.
- Installations at high altitudes or in irregular spaces where the standard calculation method is not representative.
In such cases, a comprehensive lighting design with additional luminance analysis or a pilot installation offers more certainty. Engaging professional lighting advice also helps in making the right choices before an installation is realized.
Real-world example: Van der Spek Tower Crane Lighting
A concrete example of how UGR considerations play out in practice is the project at Van der Spek. This company works with tower cranes where the lighting situation is particularly challenging: operators in the crane cabin look down from a high, moving position towards the worksite, while bystanders on the ground look up towards the light sources on the crane. Glare in both directions had to be prevented.
The technical challenge lay in the combination of limited mounting possibilities on the crane structure, constant vibrations during operation, and varying viewing angles due to the crane's rotational movement. Fixtures with focused optics and a tight beam of light were chosen so that the light falls on the work floor without operators or passers-by looking directly into the light source. Ease of maintenance also played a role: fixtures had to be easily replaceable without the crane having to be completely taken out of service.
The lesson learned directly relates to the topic of this article: a standard UGR calculation for a fixed space is not sufficient for dynamic applications such as crane lighting. The viewing position changes constantly, which means glare risks must be assessed from multiple angles. More on this and similar projects can be found on the JEL Products's Projects Page.
How JEL Products Helps You Choose the Right Lighting for Your Workspace
JEL Products guides you through the entire process, from the initial lighting challenge to a fully functional installation. Whether it involves workplace lighting in a production hall, lighting on mobile machinery, or complex outdoor installations on industrial sites—our approach is always tailored to the specific environment and its requirements.
Here's what JEL Products specifically offers:
- Lighting calculations including UGR analysis based on photometric data of your own fixtures.
- Advice on the correct luminaire selection based on task class, environmental requirements, and applicable standards such as NEN-EN 12464-1.
- Fixtures with glare-free optics and full-cutoff technology for environments where visual comfort and safety are paramount.
- Total solutions for both interior and exterior lighting, including engineering, installation, and commissioning.
- Specialized knowledge of extreme environments, from high temperatures to corrosive conditions and ATEX zones.
Would you like to know what UGR value is achievable in your situation and which fixtures are suitable for it? Get in touch Contact JEL Products for a no-obligation consultation.