Sizing
How many shop lights for a 20x20 two-car garage
A 20 x 20 ft garage (400 sq ft) needs about 39,216 lumens of fixture output for general shop work at 50 footcandles, which is 10 fixtures at 4,000 lumens. Detail work at 100 footcandles needs 78,431 lumens, or 20 fixtures. Paint the walls white and general lighting drops to 9.
Fixture counts for this garage
| Case | Lumens needed | Fixtures (4,000 lm) | Fixtures (9,000 lm) |
|---|---|---|---|
| General work, average walls | 39,216 | 10 | 5 |
| General work, white walls | 33,613 | 9 | 4 |
| General work, dark walls | 52,288 | 14 | 6 |
| Detail work, average walls | 78,431 | 20 | 9 |
Lumens needed = footcandles x area / (utilization x light loss). We use 0.6 for average walls, 0.7 for white and 0.45 for dark, and 0.85 for light loss as the dirt and age allowance. These are conventions, not code values.
Layout and load
For general work that is about 3 rows of 4 fixtures running across the 20 ft width, about 6.7 ft between rows. At 40 W per fixture the load is 400 W, 3.3 A at 120V, which a single 15 A lighting circuit carries at 80 percent with room for about 36 fixtures. Aim the rows over benches and machines rather than the center of the room, and put a second switch on the bench rows so detail work gets its extra light without lighting the whole bay.
In a 2-car bay you will rarely light the whole floor at once: put each lane on its own switch.
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Frequently asked questions
Are 4 ft LED shop lights bright enough for a garage workshop?
A typical 4 ft LED strip is rated 4,000 to 5,000 lumens. In this 20x20 two-car garage 10 of them reach the 50 footcandle general-work target; for fine layout work at 100 footcandles you need 20, or task lights at the bench.
This page is researched guidance, not professional electrical, engineering or safety advice. Circuits, loads and clearances depend on your house, your service and your town: have a licensed electrician confirm any wiring, and check local code and each manufacturer's manual before you act.
