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

Recessed lights for a 10 × 24 ft home office with a 8 ft ceiling

Recessed lights needed
18lights
3 × 6 grid, about 3.3 ft apart in a 10 × 24 ft home office
Layoutacross the 10 ft dimension × along the 24 ft dimension3 × 6
Spacing (rule of thumb)half of the 8 ft ceiling4ft
Actual spacing to mark outafter rounding to whole fixtures3.3 × 4ft
First light from the wallhalf a spacing — closer washes the wall, further leaves dark corners1.7 × 2ft
Room area240ft²
Target light levelsustained close work40fc
Total lumens needed9,600lm
Lumens per fixtureabout 7 W each in LED533lm
Room width
10 ft
Room length
24 ft
Ceiling height
8 ft
Room
home office

The grid

Spacing for recessed cans is ceiling height divided by two. A 8 ft ceiling gives 4 ft, which across a 10 × 24 ft room works out to a 3 × 6 grid — 18 lights.

Rounding to whole fixtures moves the real spacing to 3.3 × 4 ft. Mark the ceiling off those numbers, not off the rule of thumb. The first row sits 1.7 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

240 ft² at 40 footcandles needs 9,600 lumens in the room, which is 533 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 3 × 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 ft here. Rounding to whole fixtures moves it to 3.3 × 4 ft — mark the ceiling off the real numbers, not the rule.
  • 533 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.
  • Home office is a task space. 40 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 × 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

Read more