Primary audience: Facility managers
Use the high bay lighting calculator to estimate fixture count, approximate spacing and watts from published Allmax output.
Define the task before choosing a light level
A warehouse can contain bulk storage, active picking, packing benches and loading areas under one roof. Each area has a different visual task. Reading small labels on vertical racks is different from moving large pallets across an open floor. Mark those tasks before assigning a single average light level to the building.
Foot-candles measure light reaching a surface: one foot-candle is one lumen per square foot. Lux uses lumens per square metre. Fixture lumens describe the source, so dividing total fixture lumens by floor area ignores the light that misses the task or is lost along the way.
For early discussion, a typical IES-style planning band for active warehouse tasks is roughly 10–30 foot-candles, depending on item and label size. The Teamsters warehouse-lighting guidance gives 10 and 30 foot-candle examples based on older IES recommendations. This is a general planning range, not a code requirement or a prescribed target for your building. Detailed work may need separate task lighting. Have the lighting designer establish the maintained target and calculation plane from the actual work, occupants and applicable project requirements.
Apply the general lumen method
The basic estimate is: fixture count equals target foot-candles multiplied by area in square feet, divided by fixture lumens multiplied by the coefficient of utilization and light-loss factor. Round the result up for the initial layout. This formula estimates average illumination; it does not calculate individual bright or dark points.
| Input | Meaning | Where to establish it |
|---|---|---|
| Target foot-candles | Maintained light at the task | Project lighting criteria |
| Area | Floor area served by this calculation | Measured plan |
| Fixture lumens | Output at the selected configuration | Exact model documentation |
| Utilization coefficient | Fraction reaching the calculation plane | Photometry and room geometry |
| Light-loss factor | Allowance for output and dirt losses | Design and maintenance assumptions |
Do not choose the two factors merely to produce the desired quantity. Room proportions, surfaces, optics and maintenance affect them. A dark ceiling, high shelving or dirty environment can change the estimate. Record the assumptions so a reviewer can reproduce the arithmetic and identify what still needs confirmation.
Work through an illustrative calculation
Consider a hypothetical 10,000-square-foot space, a 20-foot-candle target, a 20,000-lumen fixture, a utilization coefficient of 0.60 and a light-loss factor of 0.80. These are teaching inputs, not Allmax model specifications or a design recommendation. The effective output in the denominator is 20,000 × 0.60 × 0.80 = 9,600 lumens.
The preliminary count is 20 × 10,000 ÷ 9,600 = 20.83, rounded up to 21 fixtures. That result says nothing about where those fixtures belong. An arrangement of 21 units may still leave dark rack faces, obstruct a service route or create glare at an operator’s normal viewing angle.
Test how the estimate changes before treating it as an order quantity. If the same illustrative utilization coefficient falls to 0.50, the calculation becomes 200,000 ÷ 8,000 = 25 fixtures. The change shows why assumptions matter. Replace every teaching input with the project’s actual values, then calculate the layout. Do not use this example as a lumens-per-square-foot promise.
Match the estimate to published fixture data
Compare the UHB26 UFO high bay, MLH06 linear high bays and FLS21 linear high bay using the model tables. The warehouse application page collects their published output, power and voltage figures. Choose a specific row and setting before using a lumen value.
A maximum output entry must remain tied to its configuration. A selectable fixture running at a lower setting cannot automatically use the maximum figure in the calculation. If the exact setting’s output is not published, request it. Where a product table separates output by colour temperature, carry that condition into the fixture schedule.
Optic choice is equally important. MLH06’s published options include aisle and narrow optics alongside prismatic optics. Use the IES file for the selected configuration when building the layout. Do not assume the utilization coefficient or spacing from one optic applies to another because the housing and wattage match.
Review the layout and commissioning plan
Check horizontal illumination where people travel or work, and vertical illumination where they read labels or identify stored goods. Review minimum values and uniformity as well as averages. A single average can hide an aisle end, dock threshold or rack face that receives too little light.
Include racks, beams, ducts and other obstructions in the design information. Record surface reflectances and identify whether daylight is part of the calculation. If work continues after dark, daylight cannot substitute for the required night-time electric lighting. Controls should also preserve the intended lighting when the space is occupied.
Ask for the calculation report and fixture schedule together. After installation, verify output settings, sensor behaviour and representative light readings against the agreed plan. Keep the instrument position and task plane in the record so future checks are comparable. Our site does not publish a project-specific warehouse layout; request the fixture documents for your designer. Consult the IES industrial-lighting committee for the applicable industrial-lighting recommended practice.
Document checklist for the handoff:
- Existing fixture inventory, condition photographs and occupied operating hours.
- Task-plane criteria, rack layout and designer-approved calculation assumptions.
- Proposed model schedule, matching photometric files and light-loss assumptions.
- Commissioning measurements and a record of final output and sensor settings.
Related guides
- High Bay Mounting Height: Output, Optics and Task Planes
- Commercial Lighting Retrofit Audit: A Sales Rep Checklist
- Linear High Bay vs UFO: Choosing Warehouse Fixtures
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