Recessed Lighting
Room size and what happens in it — the fixture count, the grid they go in, and how far off the wall to start.
Buy this many
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fixtures · — grid- Room area
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- Light needed
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- Spacing
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- Off the wall
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- Total wattage
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Cans no further apart than half the ceiling height.
How many cans a room needs
Lighting design starts with foot-candles — lumens landing on each square foot of floor. A living room reads comfortably at about 20, a kitchen wants 40 over the working surfaces, a bench in a garage wants 50 or more. Multiply the target by the room's area and you have the lumens the ceiling has to deliver; divide by what one fixture puts out and you have the count.
Then the count has to become a layout. Fixtures spaced further apart than half the ceiling height leave scalloped shadows between them, so an 8 foot ceiling wants them no more than 4 feet apart. The first row starts about half a spacing off the wall — close enough to light the perimeter, far enough not to glare off it. The calculator lays the count into a grid shaped like the room and tells you when the spacing has drifted too wide.
Light level by room
| Room | Foot-candles | 10 × 12 room | 14 × 16 room |
|---|---|---|---|
| Hallway, closet | 10 | 2 fixtures | 4 fixtures |
| Living room, bedroom | 20 | 4 fixtures | 6 fixtures |
| Bathroom, dining | 30 | 6 fixtures | 9 fixtures |
| Kitchen, office | 40 | 6 fixtures | 12 fixtures |
| Workshop bench | 50 | 9 fixtures | 16 fixtures |
Counts assume 800-lumen trims, the common 9–12 watt LED. Higher-output fixtures cut the number but not the spacing rule — six bright cans spread 6 feet apart still scallop.
Dimming is part of the plan
Size for the brightest thing the room does, then dim for the rest. A kitchen laid out for 40 foot-candles at full output is a perfectly pleasant evening room at 30 % on a compatible dimmer. The opposite — a room lit for the evening and asked to do homework — cannot be fixed without cutting more holes.
On the counter
The assumptions this calculator ships with — every one is adjustable in the form.
- Light level
- Foot-candles by room use — the IES-style figures in the dropdown
- Fixture output
- 800 lumens by default, a typical 9–12 W LED recessed trim
- Spacing rule
- Fixtures no further apart than half the ceiling height
- Layout
- A grid proportioned to the room; the count rounds up to fill it
Questions from the aisle
How many recessed lights in a 12x12 room?
A 144 square foot living room at 20 foot-candles wants about 2,900 lumens — four 800-lumen cans, laid out two by two. The same room as a kitchen at 40 foot-candles needs about eight, which lays out as a three by three grid of nine. The room's job, not its size alone, sets the count.
How far apart should recessed lights be?
No further apart than half the ceiling height: 4 feet on an 8 foot ceiling, 5 feet on a 10 foot one. Wider than that and the floor shows scallops of light and shadow between fixtures.
How far from the wall should the first row be?
About half the spacing — roughly 2 to 2.5 feet on a standard ceiling. Closer than 18 inches and the trim washes the wall instead of lighting the room; further out and the perimeter goes gloomy.
Are 4 inch or 6 inch cans better?
Six-inch fixtures throw a wider pool and cover a room in fewer holes; four-inch reads cleaner on a modern ceiling and suits task lighting over a counter. Lumens matter more than aperture — this calculator asks for lumens for exactly that reason.