KelvinPlanHow much light each room needs, and what colour it should be.

Recessed lights for a 16 × 28 ft bathroom with a 9 ft ceiling

Recessed lights needed
24lights
4 × 6 grid, about 4 ft apart in a 16 × 28 ft bathroom
Layoutacross the 16 ft dimension × along the 28 ft dimension4 × 6
Spacing (rule of thumb)half of the 9 ft ceiling4.5ft
Actual spacing to mark outafter rounding to whole fixtures4 × 4.7ft
First light from the wallhalf a spacing — closer washes the wall, further leaves dark corners2 × 2.3ft
Room area448ft²
Target light levelgeneral light — the mirror needs light from the sides, not above30fc
Total lumens needed13,440lm
Lumens per fixtureabout 7 W each in LED560lm
Room width
16 ft
Room length
28 ft
Ceiling height
9 ft
Room
bathroom

The grid

Spacing for recessed cans is ceiling height divided by two. A 9 ft ceiling gives 4.5 ft, which across a 16 × 28 ft room works out to a 4 × 6 grid — 24 lights.

Rounding to whole fixtures moves the real spacing to 4 × 4.7 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

448 ft² at 30 footcandles needs 13,440 lumens in the room, which is 560 lumens per fixture — around 7 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 4 × 6 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 × 4.7 ft — mark the ceiling off the real numbers, not the rule.
  • 560 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.
  • 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 4 × 6 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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