How many recessed lights — and exactly where
Recessed Lighting Calculator
Enter your room dimensions, ceiling height and how the room is used. The calculator applies the lumen method and the ceiling-height spacing rule — the same math lighting designers use — to give you fixture count, spacing and distance from the walls, with a layout diagram you can hand to an electrician.
How the Calculator Works
Step 1 — Total light (the lumen method). Multiply the room's square footage by its target light level in footcandles: 10–20 for living spaces, 30 for dining, 35–40 for kitchens (70–80 over task areas and in baths). That gives total lumens; divide by your fixture's output for the fixture count.
Step 2 — Spacing (the ceiling-height rule). Divide ceiling height by two for the maximum distance between fixtures — 4 feet apart under an 8-foot ceiling, 5 feet under a 10-foot ceiling. The first row sits half a spacing from the wall, which is why 2–3 feet is the usual wall offset.
Step 3 — The grid. The calculator arranges the count into the most even rows-and-columns grid for your room's proportions and reports the exact spacing each direction. Always put the result on a dimmer: a layout sized for cleaning brightness should dim to dinner-party level.
Recommended Light Levels by Room
| Room | Footcandles | Lumens for 150 sq ft | 6" LED fixtures (1100 lm) |
|---|
| Hallway | 5–10 | ~1,200 | 1–2 |
| Media room | 10 | ~1,500 | 2 |
| Living room / bedroom | 10–20 | ~2,250 | 2–3 |
| Dining room | 30 | ~4,500 | 4 |
| Kitchen (ambient) | 35–40 | ~5,300 | 5 |
| Home office | 60–70 | ~9,800 | 9 |
| Kitchen task / bathroom | 70–80 | ~11,300 | 10 |
Levels follow common IES-derived residential guidance. Rooms with dark walls or matte finishes absorb more light — designers often add 10–20% in saturated, low-sheen schemes.
Frequently Asked Questions
How many recessed lights do I need for a 12x12 room?
For a 12x12 bedroom or living room with an 8-foot ceiling: four 750–1100 lumen fixtures in a 2x2 grid, about 6 feet apart and 3 feet off the walls. A 12x12 kitchen needs six to nine, because kitchens call for two to three times the light of a living space.
How far apart should recessed lights be?
Divide ceiling height by two for the maximum spacing that still reads even — 4 feet under an 8-foot ceiling, 5 feet under a 10-foot ceiling. Most general layouts land between 4 and 6 feet.
How far from the wall should recessed lights be?
Half the fixture spacing — typically 2 to 3 feet. Tighter placement scallops the wall; wider leaves the room's edges dim. To deliberately wash art or cabinetry, drop to 18–24 inches.
Should I use 4-inch or 6-inch recessed lights?
6-inch fixtures are the general-lighting workhorse, especially on ceilings 9 feet and up. 4-inch trims look more tailored in small rooms, modern interiors and task zones — you just need a few more. Thin LED wafers install without a can and suit shallow joist bays.
Do recessed lights need to be on a dimmer?
Yes. Size the layout for full task brightness, then dim to suit the moment. One properly sized, dimmable layout replaces the "too many switches, never right" ceiling most homes live with.
This calculator is built and maintained by Nakada Design, the Los Angeles marketing agency for
interior designers and
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