Recessed Lighting Calculator
Find out how many recessed lights you need and exactly where to put them. Enter your room dimensions, ceiling height, and room type to get the total lumens required, the number of fixtures, the ideal spacing, and a suggested grid layout.
Typical 6" LED: 650–1,200 lm. Typical 4" LED: 400–650 lm.
How Many Recessed Lights Do I Need?
The number of recessed lights you need equals the room's square footage times the lumens required per square foot, divided by the lumens each fixture produces. Every room type has a recommended light level: work areas like kitchens and bathrooms need bright, even light, while bedrooms and hallways need far less.
Formula: Number of Lights = (Room Sq Ft × Lumens per Sq Ft) ÷ Lumens per Fixture
Recommended lumens per square foot by room type:
| Room Type | Lumens per Sq Ft | Why |
|---|---|---|
| Kitchen | 35 lm/sq ft | Task lighting for counters and prep areas |
| Bathroom | 40 lm/sq ft | Bright, even light for grooming |
| Home Office | 35 lm/sq ft | Reduces eye strain for desk work |
| Living Room | 20 lm/sq ft | Comfortable ambient light; layer with lamps |
| Bedroom | 15 lm/sq ft | Softer, relaxing light levels |
| Hallway | 10 lm/sq ft | Safe navigation lighting |
Worked example: 12 × 14 kitchen
A 12 × 14 foot kitchen is 168 square feet. At 35 lumens per square foot, it needs 168 × 35 = 5,880 lumens. Using standard 6" LED recessed lights at 650 lumens each: 5,880 ÷ 650 = 9.05, so plan on 9–10 lights. In practice, a 10 or 12-light grid gives an even ceiling pattern — or step up to 900-lumen fixtures and use 7–8 lights instead.
These are general-lighting targets. If the room has strong natural light or you layer in pendants, under-cabinet lights, or lamps, you can land at the low end. Dark cabinets, dark paint, and vaulted ceilings push you toward the high end. For commercial foot-candle calculations, use our lighting calculation tool.
Recessed Lighting Spacing: The Ceiling-Height Rule
The classic rule for recessed lighting layout: divide the ceiling height by 2 to get the spacing between fixtures, then place the outer row half that distance from the walls. This produces even, overlapping pools of light with no dark bands between fixtures.
Spacing between lights: Ceiling Height ÷ 2
Distance from walls: Spacing ÷ 2
With a standard 8-foot ceiling, that means recessed lights about 4 feet apart and 2 feet from the walls. A 9-foot ceiling gives 4.5-foot spacing (2.25 ft from walls); a 10-foot ceiling gives 5-foot spacing (2.5 ft from walls). Keeping the outer lights about 2 feet from the wall also washes light down cabinets and walls instead of leaving the perimeter in shadow.
Grid layout example: 12 × 14 room, 8 ft ceiling
Target spacing is 8 ÷ 2 = 4 feet. Along the 14-foot length, a column every ~3.5 feet gives 4 columns (starting 1.75 ft from the end walls). Across the 12-foot width, a row every 4 feet gives 3 rows (starting 2 ft from the side walls). That's a 3 × 4 grid of 12 lights— right in line with the 9–10 lights the lumen formula calls for, with a perfectly even ceiling pattern.
Two practical adjustments: pull lights slightly toward countertops, artwork, or reading areas you want to highlight rather than centering blindly on the room, and keep fixtures at least 2 feet from cabinet faces so you light the counter, not the top of your head.
Choosing Fixture Size and Output
| Fixture | Typical Output | Best Use |
|---|---|---|
| 4" recessed / wafer | 400–650 lumens | Accent and task lighting, small rooms, hallways, modern minimal look |
| 6" recessed / wafer | 650–1,200 lumens | General lighting in kitchens, living rooms, bedrooms — the standard choice |
Wafer (canless) LEDshave become the default for new installs and retrofits: the driver sits in a small junction box above the ceiling, so they fit in shallow joist bays and under insulation where a traditional can housing won't. Most are IC-rated and airtight, and many offer selectable color temperature on the fixture itself.
Color temperature matters as much as lumens. Use 2700K–3000K (warm white) in living rooms and bedrooms for a cozy, incandescent-like feel, and 3500K–4000K (neutral to cool white) in kitchens, bathrooms, and workspaces where crisp, accurate light helps with tasks. Keep every fixture in one room the same temperature.
Circuit Load: How Many Lights on a 15 Amp Circuit?
Modern LED wafer lights draw only 9–15 watts each, so circuit capacity is rarely the limit anymore. A 15-amp, 120-volt circuit provides 1,800 watts — 1,440 watts applying the NEC 80% guideline for continuous loads — which is theoretically 100+ LED wafers. In practice, the NEC counts each fixture at its rated volt-amps (the luminaire label), and good design keeps lighting circuits well under capacity, so dozens of recessed LEDs comfortably fit on a single 15A lighting circuit.
The old rule of thumb came from 60-watt incandescent cans: 1,440 W ÷ 60 W = about 24 fixtures maximum on a 15-amp circuit at 80% load. If you're retrofitting a house wired in that era, LEDs free up enormous headroom on existing circuits. To size the breaker and wire for a new lighting circuit, use our breaker size calculator and review branch circuit requirements.
Frequently Asked Questions
How many recessed lights for a 12x12 room?
A 12x12 room is 144 square feet. For a kitchen (35 lumens per sq ft) you need about 5,040 lumens — roughly 8 six-inch LED lights at 650 lumens each, laid out in a 3 × 3 grid. For a living room (20 lm/sq ft) you need about 2,880 lumens, or 4–5 lights. For a bedroom (15 lm/sq ft), about 2,160 lumens, or 4 lights in a 2 × 2 grid.
How far apart should recessed lights be?
Use the ceiling-height rule: divide the ceiling height by 2 to get the spacing between fixtures, and place the outer lights half that distance from the walls. With a standard 8-foot ceiling, space recessed lights about 4 feet apart and 2 feet from the walls. With a 10-foot ceiling, space them about 5 feet apart and 2.5 feet from the walls.
How many can lights on one switch?
A switch does not limit the number of lights — the circuit does. A standard 15-amp switch can control every light the circuit can carry. With 9–15W LED recessed lights, that is far more fixtures than any room needs, so in practice you can put an entire room's recessed lighting (often 6–12 lights) on one switch or dimmer. Just confirm the dimmer's wattage rating covers the total LED load.
How many lumens do I need per square foot?
It depends on the room and task. Kitchens and home offices need about 35 lumens per square foot, bathrooms about 40, living rooms about 20, bedrooms about 15, and hallways about 10. Multiply the room's square footage by the lumens per square foot to get the total lumens, then divide by the lumens per fixture to get the number of lights.
What size recessed lights should I use?
Six-inch (or 6-inch wafer) lights at 650–1,200 lumens are the standard choice for general lighting in kitchens, living rooms, and bedrooms. Four-inch lights at 400–650 lumens work well for accent lighting, task lighting, small rooms, and modern low-profile looks — you just need more of them to reach the same total lumens.
How many recessed lights can I put on a 15 amp circuit?
A 15-amp, 120-volt circuit provides 1,800 watts, or 1,440 watts at the NEC 80% continuous-load guideline. Modern LED wafer lights draw only 9–15 watts each, so 100 or more could theoretically fit — in practice the fixture count is limited by the luminaire's rated volt-amps and good design, not the LEDs. With old 60-watt incandescent cans, the practical limit was about 24 fixtures.
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