How Many High Bay Lights Do I Need? A Warehouse Lighting Guide
Almost every call we get starts the same way: "I've got a 60 by 100 shop with 20 foot ceilings — how many lights?" Here's how to work it out yourself. If you'd rather just have us do it, we'll lay out your building free: 817-440-4862.
Step 1: How bright does the space need to be?
Lighting brightness at the floor is measured in foot-candles. Different work needs different levels:
| Space | Foot-candles |
|---|---|
| Bulk storage, cold storage | 10–15 fc |
| General warehouse, racking aisles | 20–30 fc |
| Manufacturing, assembly | 30–50 fc |
| Auto service bays, machine shops | 50–75 fc |
| Detail bays, inspection, paint work | 75–100 fc |
| Gyms and sports courts | 50–75 fc |
Step 2: Do the rough math
The quick version:
Total lumens needed = square footage × target foot-candles
Then divide by the lumens per fixture, and add about 20 percent for light lost to walls, dirt and fixture aging.
Example. A 6,000 sq ft shop wanting 30 foot-candles needs about 180,000 lumens. Using 150W high bays at roughly 20,000 lumens each, that's 9 fixtures. Add the 20 percent margin and call it 11. Lay them out in a grid — three rows of four works nicely in a rectangular building.
Step 3: Pick the wattage by ceiling height
Ceiling height matters more than floor area. The higher the fixture, the more output it takes to land usable light on the floor.
| Ceiling height | Fixture wattage | Spacing |
|---|---|---|
| 10–14 ft | 100W–150W | 15–20 ft apart |
| 15–20 ft | 150W–200W | 20–25 ft apart |
| 20–25 ft | 200W–240W | 25–30 ft apart |
| 25–35 ft | 300W–400W | 30–40 ft apart |
A useful rule: space fixtures about 1 to 1.5 times the mounting height apart. Fixtures 20 feet up go roughly 20 to 30 feet apart. Closer spacing gives more even light with fewer shadows; wider spacing saves money but gives you bright pools and dark gaps.
Step 4: UFO or linear?
UFO (round) high bays throw a circular pattern. Use them over open floor: bulk storage, shop floors, gyms, anywhere you want an even grid of light.
Linear high bays throw a rectangle. Use them over rows: racking aisles, service bays, assembly lines, long narrow buildings. The light follows the aisle instead of spilling onto the tops of the shelves.
Plenty of buildings use both — linear over the racking, UFOs over the open staging area.
Step 5: Pick a color temperature
- 5000K — daylight white. The default for warehouses, shops and garages. Looks bright and makes colors read accurately.
- 4000K — neutral. A little softer. Good for spaces where people sit and work all day, or mixed retail and warehouse.
- 3000K — warm. Rare in industrial work; used in showrooms and customer-facing areas.
Most of our high bays let you switch between all three on the fixture, so you can try it before you commit.
Common mistakes
- Matching old fixture count one-for-one. LED throws light more efficiently. You often need fewer fixtures than the metal halides you're replacing — but at higher ceilings you sometimes need the same count at a third of the wattage.
- Ignoring the racking. Tall shelves block light. Aisle lighting needs linear fixtures aimed down the aisle, not round ones between them.
- Buying on watts instead of lumens. Watts measure what you pay for; lumens measure what you get. Two 150W fixtures can differ by 30 percent in output.
- Forgetting the rebate. DLC Premium fixtures qualify for utility rebates that can cover a real chunk of the cost. Check before you buy, not after.
Just tell us the building
Send ceiling height, length and width, and what happens in the space. We'll come back with a fixture count, a wattage and a spacing plan, free. 817-440-4862, or use the contact form. DFW customers can pick up in Burleson.