How far apart should high bay lights be?

The short answer: start with the mounting height. If your ceiling is 20 feet high, space the lights 15 to 20 feet apart. For 30‑foot ceilings, push that to 20–30 feet between fixtures. That assumes a standard wide beam (around 90–110 degrees) and good reflectors. Tighter beam angles or higher required footcandles mean you’ll need to shrink that distance. The goal is overlap—you want the cones of light to meet at task height (usually three feet off the floor) without leaving dark stripes in the aisles.

But don’t just guess. Get your room layout and workplane requirements first. A warehouse with tall racking needs tighter spacing in the aisles (maybe 1.2 to 1.5 times the mounting height), while open floor areas can go looser—up to 1.8 times the height. Always check the photometric plan. As a rule of thumb, for industrial bays, space equals mounting height for uniform lighting. For retail or detailed assembly, cut that to 0.8 to 1.2 times height. If you can’t run a simulation, lay out a test grid and walk the floor before you fix everything in place.