Electrical & Lighting · Layout planner
Recessed Lighting Calculator
This recessed lighting calculator tells you how many can lights your room needs, how far apart to space them, and how far from the walls, then draws the layout so you can mark the ceiling. It checks both brightness (lumens) and even coverage (spacing).
Your room
Typical: 10 to 20 fc. Color: 2700K to 3000K.
Foot-candles (lumens per sq ft). Set by room type, edit if you like it brighter.
4 in LED: usually 500 to 800 lm.
Check the box. Adjustable-lumen wafers list each setting.
Blue dimensions are center to center. Mark these on the ceiling, then shift a light a few inches if it lands on a joist.
How the recessed lighting calculator works
Most calculators only divide lumens by fixtures, which gives you the right brightness but can leave dark corners. Others only use spacing, which can double the light you need. We run both checks and use the larger count, then round up to a full grid so the ceiling looks deliberate.
Brightness comes from foot-candles: one foot-candle is one lumen spread over one square foot. Multiply the room area by the target for the room type to get total lumens, then divide by the lumens printed on the box.
Coverage comes from the spacing rule below. Each light sits half a spacing from the walls, so the math is simply room length divided by the number of lights across it.
Recessed lighting spacing: the half-ceiling-height rule
Here is the rule lighting designers start with: divide the ceiling height by 2 to get the spacing between lights. An 8 ft ceiling gets lights about 4 ft apart, and a 10 ft ceiling about 5 ft apart. Higher ceilings let each beam spread wider before it hits the floor, so you can space them farther.
Treat three quarters of the ceiling height as the limit. Past that, the pools of light stop overlapping and you see dim bands between fixtures. The distance from the wall is half the spacing, which lands at 2 to 3 ft in most rooms.
Before you commit, find the ceiling joists. A good stud finder maps the framing in a minute (our guide to using a stud finder covers ceilings too). Shift a row a few inches to miss a joist. Nobody will notice 3 in, but everyone notices a crooked row.
| Ceiling | Ideal spacing | Max spacing | From wall |
|---|---|---|---|
| 8 ft | 4' | 6' | 2' to 3' |
| 9 ft | 4' 6" | 6' 9" | 2' 3" to 3' 5" |
| 10 ft | 5' | 7' 6" | 2' 6" to 3' 9" |
| 12 ft | 6' | 9' | 3' to 4' 6" |
How many lumens each room needs
These targets are for general (ambient) light from recessed fixtures, based on IES residential guidance. Kitchens and offices need more because you work under them. Living rooms and bedrooms look better a little dimmer, with lamps doing the rest.
| Room | Target used | Typical range | Lumens per 100 sq ft | Color temperature |
|---|---|---|---|---|
| Kitchen | 50 fc | 30 to 50 fc (70+ at counters) | 5,000 lm | 3000K to 4000K |
| Living room / family room | 20 fc | 10 to 20 fc | 2,000 lm | 2700K to 3000K |
| Bedroom | 20 fc | 10 to 20 fc | 2,000 lm | 2700K to 3000K |
| Bathroom | 40 fc | 30 to 50 fc | 4,000 lm | 3000K to 3500K |
| Hallway / stairs | 10 fc | 5 to 15 fc | 1,000 lm | 2700K to 3000K |
| Home office | 40 fc | 30 to 50 fc | 4,000 lm | 3500K to 4000K |
| Basement / rec room | 20 fc | 15 to 30 fc | 2,000 lm | 3000K to 3500K |
| Garage / workshop | 50 fc | 30 to 75 fc | 5,000 lm | 4000K to 5000K |
4 in vs 6 in, wafer vs can lights
6 inch lights put out 800 to 1,200 lumens and suit living rooms, basements and garages. 4 inch lights give 500 to 800 lumens and look cleaner in kitchens, baths and halls. Switch sizes in the calculator and watch the count change.
Wafer (canless) LED lights are half an inch thick with a small remote junction box. They install from below through a single hole, need no housing, and cost less per light. That makes them our pick for almost every remodel. Can lights still make sense when you want swappable trims, adjustable gimbals, or a sloped-ceiling housing.
Pick color temperature by room: 2700K to 3000K for living spaces and bedrooms, 3000K to 4000K for kitchens and baths, and 4000K or higher for a garage or shop. Many wafers have a switch on the junction box to choose. Put every group on an LED-compatible dimmer and check the fixture maker's compatible dimmer list.
Buy IC-rated and airtight
Recessed lighting mistakes to avoid
- Placing lights by eye. Snap chalk lines or use a laser and mark every hole from the layout above before you cut anything.
- Centering a grid on the room when furniture is off center. In kitchens, center rows over the counter edge (about 24 to 30 in from the wall), not the middle of the floor, so you do not work in your own shadow.
- Ignoring the ceiling fan. Keep lights clear of the blade sweep or they strobe through the blades. Size the fan first with our ceiling fan size calculator.
- Mixing color temperatures. One 4000K light in a row of 3000K ones sticks out. Buy the whole room from one box.
- Forgetting the outside. If you are wiring new circuits anyway, it is a good time to plan landscape lighting for the yard.
Run your room through the recessed lighting calculator above, print the layout, and you will cut every hole once.
Frequently asked questions
How many recessed lights do I need for a 12x12 room?
Four 6-inch lights in a 2 x 2 grid cover a 12 x 12 living room or bedroom with an 8 ft ceiling. That puts them 6 ft apart and 3 ft from each wall, with about 4,000 lumens for 144 sq ft. With 650 lumen 4-inch lights you need 6 (2 rows of 3) to reach the same brightness.
How far apart should recessed lights be?
Space recessed lights about half the ceiling height apart, so 4 ft on an 8 ft ceiling and 5 ft on a 10 ft ceiling. You can stretch to about three quarters of the ceiling height (6 ft on an 8 ft ceiling) before dim patches show up between the pools of light.
How far should recessed lights be from the wall?
Put the first row half the spacing from the wall, which works out to 2 to 3 ft in most rooms. Go closer, around 18 in to 2 ft, only when you want to wash a wall or light artwork. Closer than that leaves hot spots and harsh scallops on the wall.
Should I use 4 inch or 6 inch recessed lights?
Use 6 inch lights for general lighting in living rooms, basements and garages, where fewer, brighter fixtures make sense. Use 4 inch lights in kitchens, bathrooms, hallways and anywhere you want a cleaner ceiling or more, smaller pools of light. Modern 4 inch wafers put out 600 to 800 lumens, so they are not underpowered.
Can recessed lights touch insulation?
Only if they are IC-rated (insulation contact). Non-IC housings need at least 3 in of clearance from insulation, per the NEC. Almost every LED wafer light is IC-rated and airtight, which is one reason they have replaced old cans in remodels.
How many recessed lights can go on one circuit?
Far more than you will install. A 15 amp, 120 volt circuit can carry about 1,440 watts of continuous load, which is over 100 LED wafers at 10 to 12 watts each. The practical limit is the dimmer, since many LED dimmers are rated for only 150 to 250 watts of LED load.
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