Recessed lights for a 12 × 12 ft basement with a 9 ft ceiling
| Layoutacross the 12 ft dimension × along the 12 ft dimension | 3 × 3 |
|---|---|
| Spacing (rule of thumb)half of the 9 ft ceiling | 4.5ft |
| Actual spacing to mark outafter rounding to whole fixtures | 4 × 4ft |
| First light from the wallhalf a spacing — closer washes the wall, further leaves dark corners | 2 × 2ft |
| Room area | 144ft² |
| Target light levelfinished space with little daylight | 25fc |
| Total lumens needed | 3,600lm |
| Lumens per fixtureabout 5 W each in LED | 400lm |
- Room width
- 12 ft
- Room length
- 12 ft
- Ceiling height
- 9 ft
- Room
- basement
The grid
Spacing for recessed cans is ceiling height divided by two. A 9 ft ceiling gives 4.5 ft, which across a 12 × 12 ft room works out to a 3 × 3 grid — 9 lights.
Rounding to whole fixtures moves the real spacing to 4 × 4 ft. Mark the ceiling off those numbers, not off the rule of thumb. The first row sits 2 ft from the wall — half a spacing. Closer and you get a bright band down the wall; further and the corners go dark.
What to buy, not just how many
144 ft² at 25 footcandles needs 3,600 lumens in the room, which is 400 lumens per fixture — around 5 W in LED.
That is the number to shop by, and it is the one most layout calculators leave out. A 4″ LED downlight typically runs 600–800 lm; a 6″ runs 800–1,200 lm.
Before you cut
Find the joists first. A 3 × 3 grid rarely lands clear of framing on the first attempt, and shifting a can six inches to miss a joist is invisible once the trim is on. Put the whole layout on a dimmer while the wiring is open — it costs almost nothing then and cannot be added cheaply later.
Notes
- The spacing rule is ceiling height ÷ 2, which gives 4.5 ft here. Rounding to whole fixtures moves it to 4 × 4 ft — mark the ceiling off the real numbers, not the rule.
- 400 lumens per can is the figure to shop by. A 4″ LED downlight typically runs 600–800 lm and a 6″ runs 800–1,200 lm, so you could drop to 4″ cans or dim these down.
- 25 fc is an ambient level, which is what you want here. Recessed lights alone make a room look flat; the fix is lamps and wall light, not more cans.
- Put them on a dimmer. It costs almost nothing at install, and it is the difference between a ceiling that works at dinner and one that works at 11pm.
- Check the joists before marking. A 3 × 3 grid rarely lands clear of framing on the first try, and moving a can 6 inches to miss a joist is invisible once the trim is on.
Nearby sizes
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- Recessed lights for a 12 × 12 ft basement with a 10 ft ceiling
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