The usual rule spaces recessed lights about half the ceiling height apart, with the outer ones half that distance from the walls. The calculator lays out an even grid that way, then checks the lumens against a light level for the room.
How to use this calculator
- Measure the room and the ceiling height.
- Pick the room: kitchens and bathrooms want more light than living rooms and hallways.
- Pick the size and brightness of the lights, then check the layout and the light check.
Worked examples
A living room
Room: 16 × 14 ft · Ceiling height: 8 ft · Room: Living room or bedroom · Lights: 6 in LED, about 925 lumens
- Recessed lights
- 16 lights, 4 rows of 4
- Spacing along the room
- 4.0 ft
- Spacing across it
- 3.5 ft
- Outer lights from the walls
- 2.0 ft
- Light they give
- 14,800 lumens
- Light the room needs, about
- 2,240 lumens
- Lights the light level alone needs
- 3 lights
A kitchen
Room: 14 × 12 ft · Ceiling height: 9 ft · Room: Kitchen · Lights: 6 in LED, about 1,150 lumens
- Recessed lights
- 12 lights, 3 rows of 4
- Spacing along the room
- 3.5 ft
- Spacing across it
- 4.0 ft
- Outer lights from the walls
- 1.8 ft
- Light they give
- 13,800 lumens
- Light the room needs, about
- 3,360 lumens
- Lights the light level alone needs
- 3 lights
A bathroom
Room: 9 × 8 ft · Ceiling height: 8 ft · Room: Bathroom · Lights: 4 in LED, about 900 lumens
- Recessed lights
- 6 lights, 2 rows of 3
- Spacing along the room
- 3.0 ft
- Spacing across it
- 4.0 ft
- Outer lights from the walls
- 1.5 ft
- Light they give
- 5,400 lumens
- Light the room needs, about
- 1,440 lumens
- Lights the light level alone needs
- 2 lights
A hallway
Room: 20 × 4 ft · Ceiling height: 8 ft · Room: Hallway · Lights: 4 in LED, about 600 lumens
- Recessed lights
- 5 lights, 1 rows of 5
- Spacing along the room
- 4.0 ft
- Outer lights from the walls
- 2.0 ft
- Light they give
- 3,000 lumens
- Light the room needs, about
- 800 lumens
- Lights the light level alone needs
- 2 lights
How far apart recessed lights go
Kichler, a lighting maker, divides the ceiling height by 2 for the spacing, so lights on a standard ceiling sit about half its height apart, and no more than 6 ft apart even under a high ceiling. ERCO places the outer lights at 0.5 of the spacing from the walls, and Kichler keeps them at least 2 ft away.
How much light a room needs
A foot-candle is a lumen on each square foot. LEDVANCE, a lighting maker, suggests about 10 foot-candles for living rooms and hallways and 20 foot-candles for kitchens and bathrooms, the low ends of its ranges. Those are more generous than the ambient minimums the Illuminating Engineering Society gives, about 3 foot-candles for a living room, but they suit recessed lights that do most of a room's lighting; task areas such as a prep counter want far more, 50 foot-candles.
Lumens and watts
Brightness is lumens, not watts. A six-inch LED module gives about 925 lumens on about 10.8 watts, and an LED bulb giving 800 lumens, the light of an old sixty-watt bulb, uses only 5.9 to 10.5 watts. Put recessed lights on a dimmer so a generous layout can be turned down.
Common questions
How far apart should recessed lights be?
About half the ceiling height, so roughly four feet apart on an eight-foot ceiling, and no more than 6 ft apart.
How far should recessed lights be from the wall?
About half the spacing between lights, and at least 2 ft from the wall.
How many recessed lights do I need?
Enough to cover the room on that grid and to give its light level: the calculator works out both for your room and your lights.
How many lumens does a kitchen need?
About 20 foot-candles on each square foot for general light, and more at the counters.