The number of LED luminaires you need in a hall is calculated by multiplying the desired lux value by the floor area, and then dividing that number by the luminous flux per luminaire, adjusted for lighting efficiency. For an industrial hall of 1,000 m² with a desired illumination of 300 lux, you'll quickly need dozens of luminaires, depending on the type of luminaire and mounting conditions. The sections below detail each step of that calculation and highlight the pitfalls that can lead to an incorrect result.
What factors determine how much lux you need in a hallway?
The activities taking place in a hall, the applicable safety requirements, and the relevant standards together determine the required lux level. The European standard NEN-EN 12464-1 prescribes minimum illuminance levels for each type of workspace: from 100 lux for storage areas to 500 lux or more for precise assembly work. The nature of the work is therefore the first and most important variable.
In addition to the work type, the following factors play a direct role:
- Room dimensions and ceiling height: The higher the ceiling, the more power a luminaire needs to effectively illuminate the floor. At a mounting height above 8 meters, the luminaire choice changes drastically.
- Reflectance values of walls, ceiling, and floor: Light surfaces reflect light and increase the average illuminance without additional luminaires. Dark industrial environments require more light points.
- Presence of machines and obstacles: Racks, cranes, and installations create shadow zones. Good distribution of luminaires compensates for this, but requires more calculation than an empty hall.
- Safety requirements and HSE standards: In environments with moving equipment, hazardous substances, or 24/7 operations, stricter requirements apply to minimal illuminance and uniformity.
- Maintenance factor Over time, light luminaires lose luminous flux due to soiling and light degradation. The calculation must account for this by incorporating a margin, typically a factor between 0.7 and 0.9.
For sectors such as the heavy industry Additional requirements apply due to heat, dust, or aggressive environments, which influence luminaire selection and the calculation of maintenance factors.
How do you calculate the number of luminaires with the lumen formula?
With the lumen formula, you determine how many luminaires you need based on the desired illuminance, the area, and the luminous flux per luminaire. The formula is: Number of luminaires = (Lux × Area) / (Lumens per luminaire × LLF × η). Here, LLF stands for the Light Loss Factor and η for the room's lighting efficiency.
A practical calculation example step-by-step:
- Determine the desired lux: Suppose you want 300 lux for a general production hall.
- Measure the floor area A hall measuring 40 x 25 meters has 1,000 sq m.
- Choose a luminaire: An industrial LED luminaire delivers, for example, 20,000 lumens.
- Determine the maintenance factor (LLF): In a dusty environment, you use 0.75.
- Estimate the lighting efficiency (η): For an average industrial hall with dark walls, this is approximately 0.65.
- Calculate: (300 × 1.000) / (20.000 × 0.75 × 0.65) = 300,000 / 9,750 ≈ 31 luminaires.
This number is a starting point, not an end result. The formula assumes an even distribution, which is rarely so simple in practice. Factors such as mounting pattern, light angle of the luminaire, and the presence of workstations with higher luxury requirements call for further refinement. More background on luminous flux and lumens can be found on the page about luminous flux.
What is the difference between a lighting calculation and a lighting plan?
In short: a lighting calculation tells you how much, while a lighting plan also tells you where and how. The calculation is a quantitative step that determines how many luminaires and lumens are needed to achieve the desired illuminance. The lighting plan is a comprehensive design that also specifies the positioning, beam angles, uniformity, connections, and any emergency lighting. The calculation is part of the lighting plan, not a replacement for it.
In practice, this distinction means the following:
- A lighting calculation gives you a number: you need X luminaires of Y lumens.
- A lighting plan also tells you where to place those luminaires, how to aim them, which light color is suitable for the application, and how to handle emergency lighting or zones with higher requirements.
- For complex environments with multiple zones, machines, or hazardous areas, a lighting plan is indispensable to meet standard requirements.
Many projects start with a quick calculation and then move on to a full lighting plan once the technical requirements become clearer. The same principle applies to sites and outdoor locations: a calculation determines the capacity, the plan determines the implementation. You can read more about this process on the page about Lighting advice.
What errors lead to incorrectly calculated lighting in halls?
By far the most common mistake when calculating average illumination is omitting or underestimating the maintenance factor. Anyone who calculates using the nominal lumen value of a luminaire without correction for dirt and light degradation will systematically end up too low. After a year of use, the effective luminous flux can already be 20 to 30 percent lower than the factory value.
Other common mistakes include:
- Incorrect space efficiency coefficient (η) Dark walls and high ceilings absorb a lot of light. Anyone who uses a default value without considering the actual room properties will overestimate the result.
- Ignore obstacles: Shelving, columns, and machines create shadow zones that are not included in a simple formula. Only a 3D simulation can fully visualize this.
- Luminaire selection without considering the beam angle: A narrow-beam luminaire illuminates a small zone intensively. In a wide hall without good diffusion, light and dark spots appear, even if the average lux value is correct on paper.
- Forgetting task lighting zones: Workplaces that require precision work need higher illuminance levels than the ambient lighting provides. Anyone who only calculates the average does not meet the standard for those specific zones.
- Ignore IP and IK class: In environments with dust, moisture, or vibrations, luminaires lose luminous flux faster if they are not suitable for the environment. The correct protection class is part of a correct calculation. You can read more about this on the page about IP and IK rating.
When is a professional lighting calculation mandatory or necessary?
Once the Working Conditions Act (Arbowet) or the NEN-EN 12464 standard applies, which is the case for virtually any workspace, you are legally obliged as an employer to provide sufficient and suitable lighting at the workplace. For new construction, renovation, or expansion of industrial spaces, a documented lighting calculation is also part of the permit application or the building file.
Outside of legal requirements, a professional calculation is also practically necessary in the following situations:
- Halls with a ceiling height above 6 meters, where standard formulas are not sufficiently accurate.
- Explosive atmospheres (ATEX zones), extreme temperatures, or aggressive substances.
- Locations with 24/7 operations where maintenance is difficult to schedule and reliability is crucial.
- Projects for which subsidies or tax benefits are requested, such as the Energy Investment Allowance (EIA), which require technical substantiation.
- Complex sites or outdoor locations with multiple lighting zones and security requirements.
In all these cases, a manual formula provides insufficient certainty. Professional lighting software and a technical specialist bring all variables together into a reliable design.
Examples from practice: DFDS Terminal Lighting
A good example of how lighting calculations work out in practice is the project for DFDS, a large ro-ro terminal where ships, trucks, and handling equipment move around day and night. The technical challenges were considerable: the lighting installation had to withstand salt, moisture, and continuous vibrations from heavy equipment, while operational continuity did not allow for any downtime.
During the design process, luminaires with a high IP rating were chosen, specifically selected based on the terminal's environmental conditions. The lighting calculation explicitly considered the low reflectivity of the asphalt surface and the presence of large vehicles causing shadow zones. A standard formula would have been completely insufficient for this application, only a detailed calculation with correct maintenance factors and a simulated luminaire distribution resulted in a design that met the safety standards.
The learned lesson directly ties into the subject of this article: anyone who relies on a simple lumen formula for a complex outdoor location or terminal runs the risk of under-illumination in critical areas. The combination of a low maintenance factor, dark surfaces, and obstacles makes a professional simulation indispensable. More comparable projects can be found on projects page.
How JEL Products Helps Calculate Lighting for Industrial Facilities
JEL Products offers more than just lighting luminaires. As a specialist in industrial LED lighting, JEL Products supports organizations throughout the entire process, from lighting design to the completed installation. This includes:
- Professional lighting design: Based on the specific space, activities, and standards, an accurate lighting plan is developed, including 3D simulation and lux verification.
- Custom lighting advice: Whether it's a production hall, a workshop, a climate chamber, or an outdoor location, the right light luminaire is selected based on technical requirements, environmental conditions, and maintenance cycle.
- Total solution From engineering and foundation work to installation and commissioning. JEL Products is ISO 9001 and VCA** certified and operates in the most demanding industrial environments.
- Grant assistance: JEL Products provides assistance with applying for tax incentives and subsidies available for energy-efficient LED lighting.
Do you want to know how many light luminaires your hallway needs and which solution best fits your situation? Then contact us via JEL Products Contact Page for a no-obligation consultation.
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