Recessed lights for a 18 × 18 ft dining room with a 12 ft ceiling
| Layoutacross the 18 ft dimension × along the 18 ft dimension | 3 × 3 |
|---|---|
| Spacing (rule of thumb)half of the 12 ft ceiling | 6ft |
| Actual spacing to mark outafter rounding to whole fixtures | 6 × 6ft |
| First light from the wallhalf a spacing — closer washes the wall, further leaves dark corners | 3 × 3ft |
| Room area | 324ft² |
| Target light levelambient around a fixture over the table | 20fc |
| Total lumens needed | 6,480lm |
| Lumens per fixtureabout 10 W each in LED | 720lm |
- Room width
- 18 ft
- Room length
- 18 ft
- Ceiling height
- 12 ft
- Room
- dining room
The grid
Spacing for recessed cans is ceiling height divided by two. A 12 ft ceiling gives 6 ft, which across a 18 × 18 ft room works out to a 3 × 3 grid — 9 lights.
Rounding to whole fixtures moves the real spacing to 6 × 6 ft. Mark the ceiling off those numbers, not off the rule of thumb. The first row sits 3 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
324 ft² at 20 footcandles needs 6,480 lumens in the room, which is 720 lumens per fixture — around 10 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 6 ft here. Rounding to whole fixtures moves it to 6 × 6 ft — mark the ceiling off the real numbers, not the rule.
- 720 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 either size covers it.
- 20 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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