For even recessed-light spacing, use the rule of thumb spacing = ceiling height ÷ 2: an 8-foot ceiling wants lights about 4 feet apart, a 10-foot ceiling about 5 feet. Start the first row half a spacing (2–2.5 ft) off the wall so the perimeter isn't dark. Then sanity-check brightness against the room's foot-candle target — a kitchen wants 30–40 fc, a living room 10–20, a home office 60–80 — because spacing gives you even light, not necessarily enough light. Recessed cans are the ambient layer; counters, desks, and mirrors still want dedicated task lighting.
Laying out downlights? The recessed lighting calculator gives the spacing, the number of fixtures, and a brightness check against the room's foot-candle target — free, no signup. This guide explains the spacing rule and why you check lumens too.
📐 The spacing rule
The widely used layout rule is spacing = ceiling height ÷ 2. It comes from the “cone” of light each downlight throws: spacing lights at half the ceiling height overlaps those cones enough to avoid dark gaps and hot spots. So:
- 8-foot ceiling → lights about 4 feet apart
- 9-foot ceiling → about 4.5 feet apart
- 10-foot ceiling → about 5 feet apart
It's a starting grid, not a law — you'll nudge fixtures to dodge joists and align with the room — but it keeps the light even across the ceiling.
🧱 The wall offset
The first row shouldn't sit a full spacing from the wall, or the edges of the room go dark. Start it at half a spacing off the wall — roughly 2 to 2.5 feet on a typical ceiling. That lights the perimeter (and the artwork and cabinets that live along the walls) instead of leaving a shadowed border.
Watch the wall wash on cabinets. In a kitchen, pull the row of cans out from the wall so the light lands on the countertop, not the cabinet faces — cans set too close throw light down the cabinet fronts and leave the counter in shadow.
🔆 Even light vs enough light
Spacing solves evenness. It doesn't guarantee the room is bright enough — that's a separate check against the room's illuminance target, measured in foot-candles (fc). Rough targets from lighting-design guidance:
- Hallway 5–10 fc · Living room / bedroom 10–20 fc
- Kitchen / bathroom (general) 30–40 fc
- Home office 60–80 fc · Workshop 50–100 fc
You reach the target by combining the number of fixtures, each one's lumen output, and the room area. If the spacing grid doesn't deliver enough foot-candles, use brighter fixtures or add a couple more — the calculator flags when the layout falls short of the target.
🎯 Layers, not one grid
Recessed cans are the ambient layer — general fill light. They're not meant to do everything. The high-use zones want their own task lighting: under-cabinet lights over a kitchen counter (which wants 70–80 fc, far above the room general), fixtures at the bathroom mirror, and lamps at a reading chair. Trying to hit task levels everywhere with ceiling cans over-lights the whole room and washes it flat.
So aim the recessed layout at the room's general target, and plan task and accent lighting separately for where people actually work.
✅ The bottom line
Space recessed lights at half the ceiling height, start the first row a half-spacing (about 2–2.5 ft) off the wall, then check the fixture count and lumens against the room's foot-candle target so it's bright enough, not just even. Treat cans as the ambient layer and add task lighting where it's needed.
This is a layout and illumination tool, not a code-compliance tool — the wiring itself still follows the NEC. Plan the grid with the recessed lighting calculator, and size the circuit feeding it with the wire size calculator.
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