LED High Bay Lighting Calculator: How Many LED High Bay Lights Do You Need?

Required Foot-Candles by Application

One of the biggest variables is what's happening in your space. A warehouse storing bulk pallets has very different lighting needs than a manufacturing floor where workers read labels or operate precision equipment.

Here are general foot-candle targets by application type:

Note: These are widely accepted baselines from IESNA (Illuminating Engineering Society of North America) guidelines. If you're working in a regulated environment, such as food processing or healthcare-adjacent facilities, it's worth confirming the exact standard for your industry.

How Ceiling Height Affects Your Fixture Count (and Wattage)

Ceiling height is probably the single biggest variable most people underestimate. A 200W UFO high bay at 20 feet produces a very different floor-level light distribution than that same fixture at 35 feet.

As a general rule:

Note: Higher ceilings mean more spread and more light loss before it reaches the floor. That's why fixture spacing, beam angle, and mounting height all need to be factored in together, not just wattage or lumens alone.

A Working Example: 10,000 sq ft Warehouse, 25 ft Ceilings

Let's say you're lighting a 10,000 sq ft general warehouse (100 ft × 100 ft) with 25-foot ceilings. You need around 20 foot-candles at the floor.

You've selected a 200W UFO high bay producing 26,000 lumens with a CU of 0.75.

Calculation:

• Total lumens needed: 10,000 sq ft × 20 FC = 200,000 lumens
• Effective lumens per fixture: 26,000 × 0.75 = 19,500 lumens
• Fixtures needed: 200,000 ÷ 19,500 = ~10.3 fixtures

So you'd round up to 11 fixtures, and then lay them out in a grid pattern. In this case, something like a 4×3 arrangement with fixtures spaced roughly 25 feet apart.

Pro Tip: Keep in mind this is a baseline. The lighting design experts at Warehouse Lighting can help you refine your calculations to account for specific fixture beam angles, interreflection from walls and floors, and aisle/rack configurations.

Variables That Can Throw Off Your Estimate

Even a solid formula can be undermined by a few overlooked factors:

• Reflectance values. A white-walled distribution center with a polished concrete floor will naturally amplify your light levels. A dark powder-coated industrial environment with black racking absorbs light like a sponge. CU can swing from 0.65 to 0.90+ based on this alone.
• Rack height. In a racking warehouse, the light has to get down to pick-level, not just to the floor. If aisles are 20 feet tall with 6-inch clearance at the top, you may need to think about aisle-oriented fixtures or supplemental lighting at lower heights.
• Natural daylight. Skylights or clerestory windows can reduce the number of fixtures you need during daytime hours, which is especially relevant if you're adding occupancy sensors and daylight harvesting controls.
• Fixture spacing-to-mounting-height ratio. Most high bay fixtures have a recommended spacing-to-mounting-height (S/MH) ratio of 1.0–1.5. Exceed that and you'll get dark spots between fixtures. Go too tight, and you're overspending with diminishing returns.
• Optics and beam angle. UFO high bays typically come in 60°, 90°, and 120° beam angles. Narrower beams concentrate light at greater distances; wider beams give more even coverage at lower heights. Choosing the wrong optic for your mounting height is a common mistake.

Choosing Between UFO and Linear High Bay Fixtures

Once you have an estimate, you still need to pick the right style of fixture, and that choice affects your spacing, coverage, and the final fixture count.

In most open-warehouse applications, UFO fixtures are the workhorses. For manufacturing lines, assembly areas, or any area with defined aisles, linear high bays often win on uniformity.

UFO High Bays

UFO high bays are compact, round fixtures ideal for open-floor spaces with higher ceilings. They produce a symmetrical light distribution and work well in a grid layout. A standard UFO high bay typically ranges from 15,000 to 25,000+ lumens and is designed to replace 320-400W HID fixtures, making them a straightforward upgrade for facilities still running older metal halide or HPS systems.

Linear High Bays

Linear high bays distribute light in a long, rectangular pattern, making them a natural fit for aisles, shelving rows, and rectangular bays. They tend to provide better uniformity in racking-heavy environments. Most linear high bays available today range from 11,000 to 21,000+ lumens depending on wattage selection, and are built to replace legacy T5HO fluorescent or 250-400W HID fixtures.