How far apart should I space the lights（UFO High Bays）?
For UFO high bays, the standard rule of thumb is to space them no more than 1.2 to 1.5 times the mounting height. If your ceiling is 25 feet high, keep fixtures 30 to 38 feet apart center-to-center. Go wider than that and you'll get dark valleys between lights. Most guys in the trades use the "height-to-spacing ratio" from the photometric data. A 90° beam UFO at 30 feet wants roughly 35 to 40 foot spacing. A tighter 60° beam needs maybe 25 to 30 feet. Always measure from the floor to the fixture lens, not the roof peak.
That said, don't just trust the math blindly. Your aisle layout and racking change everything. Put a row of UFOs directly over each main aisle, not over the racks themselves. Space fixtures in a square grid for open storage or a rectangular grid for long aisles. Staggering the rows helps kill shadows if you have tall shelving. For a warehouse with 30-foot ceilings and 10-foot-wide aisles, you can push spacing to 45 feet along the aisle but keep cross-aisle spacing tighter at 30 feet. Grab a light meter and check the floor after installation—tweak the layout if you see hot spots or dark zones. Cheap laser pointers taped to the ceiling grid help visualize coverage before you drill hangers.
