How to calculate high bay lighting?

Start with the target foot-candle level for your space. For general warehousing, 10–30 foot-candles works; for detailed assembly or inspection, bump to 50–100. Measure floor area (length × width in feet), then multiply by desired foot-candles to get raw lumens needed. Example: a 100’×80’ shop at 30 foot-candles needs 240.000 lumens. But don’t stop there—account for mounting height and light loss. A 30’ ceiling kills more light than a 15’ one, so add a “utilization factor” (0.6 to 0.8 for reflective walls/ceilings) and a “maintenance factor” (0.7 to 0.85 for dirt and LED fade). Divide raw lumens by those factors to get real fixture lumens required.

Next, pick a UFO high bay with a beam angle that matches your spacing. Narrow 60° beams work for 40’+ ceilings and tight layouts; wide 120° beams suit lower heights and open floors. Use the “spacing-to-mounting-height ratio” rule: for general lighting, keep fixtures no farther apart than 1.5× their mounting height. Mounting a light at 25’? Space them roughly 35’ to 40’ apart, center to center. Then simulate with one fixture’s lumen output. Say each unit puts out 25.000 lumens. Divide the adjusted total lumens (from paragraph one) by 25.000 to get quantity. Always add 10–15% for safety. For precise layouts, run a quick DIALux or AGi32 simulation—no guesswork.