Recessed lights for a 20 × 20 ft bathroom with a 12 ft ceiling
| Layoutacross the 20 ft dimension × along the 20 ft dimension | 3 × 3 |
|---|---|
| Spacing (rule of thumb)half of the 12 ft ceiling | 6ft |
| Actual spacing to mark outafter rounding to whole fixtures | 6.7 × 6.7ft |
| First light from the wallhalf a spacing — closer washes the wall, further leaves dark corners | 3.3 × 3.3ft |
| Room area | 400ft² |
| Target light levelgeneral light — the mirror needs light from the sides, not above | 30fc |
| Total lumens needed | 12,000lm |
| Lumens per fixtureabout 18 W each in LED | 1,333lm |
- Room width
- 20 ft
- Room length
- 20 ft
- Ceiling height
- 12 ft
- Room
- bathroom
The grid
Spacing for recessed cans is ceiling height divided by two. A 12 ft ceiling gives 6 ft, which across a 20 × 20 ft room works out to a 3 × 3 grid — 9 lights.
Rounding to whole fixtures moves the real spacing to 6.7 × 6.7 ft. Mark the ceiling off those numbers, not off the rule of thumb. The first row sits 3.3 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
400 ft² at 30 footcandles needs 12,000 lumens in the room, which is 1,333 lumens per fixture — around 18 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 6.7 × 6.7 ft — mark the ceiling off the real numbers, not the rule.
- 1,333 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 this room wants 6″ cans, or more of them.
- Bathroom is a task space. 30 fc is the general level — countertops, desks and mirrors still need their own light. Ceiling cans alone put the light behind you and your own shadow onto the work.
- 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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Read more
- 2700K vs 3000K: A Difference You Only See Side by SideShown separately, almost nobody can tell 2700K from 3000K. Shown together, everybody can. That single fact decides how you should buy them.
- 3000K or 4000K in a Kitchen? Look at the Worktop, Not the ChartMost advice picks a number and defends it. The honest answer is that 3000K and 4000K are both correct, in different kitchens, and the deciding factor is what the light lands on.
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- Bedroom Lumens: The Room Where Less Is the SpecificationThe bedroom is the only room where the target is a range you should deliberately sit at the bottom of, and where the dimmest setting matters more than the brightest.