Recessed Lighting Calculator: How Many Lights & Spacing

Use this recessed lighting calculator to plan can lights for a room. Enter the room size, the ceiling height and the room type. You get how many lights to install, how far apart to space them and how far from the walls, with a check that the room gets enough light.

Room length

Room width

Ceiling height

Room

Light output per fixture

lumens

Spacing

–recessed lights

–rows × lights per row

–apart along the length

–apart along the width

–lumens needed

–lumens from the lights

Light levels use common ranges for homes. Check the fixture box for lumens, and keep fixtures rated for insulation contact (IC) where insulation touches them.

How the recessed lighting calculator works

Spacing: lights about as far apart as the ceiling is high, for general light. For an even wash of light across the walls, use half the ceiling height.
Lights along each side = room side ÷ spacing, rounded to the nearest whole number
The first lights sit half a space from the walls, so the layout is centered
Lumens needed = room area × foot-candles for the room type
If the lights don’t give enough lumens, the calculator adds a row or column until they do

Worked example

A 14 × 12 ft bedroom with an 8 ft ceiling and 4 in fixtures of about 650 lumens:

Spacing: about 8 ft, so 14 ÷ 8 = 1.75, rounded to 2, and 12 ÷ 8 = 1.5, rounded to 2
Layout: 2 × 2 = 4 lights
Along the length: 7 ft apart, 3 ft 6 in from the walls. Along the width: 6 ft apart, 3 ft from the walls.
Light check: 168 sq ft × 15 foot-candles = 2,520 lumens needed. 4 × 650 = 2,600 lumens, which is enough.

The same size room as a kitchen, at 35 foot-candles, needs 5,880 lumens. With 650 lumen fixtures that grows to 12 lights in a 3 × 4 layout. With 6 in fixtures of about 900 lumens it takes 9 lights in a 3 × 3 layout.

Lights for common rooms

For an 8 ft ceiling and general spacing:

Room	Bedroom or living room, 650 lm	Kitchen, 650 lm	Kitchen, 900 lm
10 × 10 ft	4	6	4
12 × 12 ft	4	9	6
14 × 12 ft	4	12	9
16 × 12 ft	6	12	9
20 × 14 ft	9	20	12
20 × 16 ft	9	20	16

Light levels by room

Common ranges for homes, in foot-candles (lumens per sq ft). The calculator uses the middle of each range.

Room	Foot-candles
Living room, bedroom	10 to 20
Kitchen (general), dining room	30 to 40
Bathroom, home office	20 to 50
Hallway, entry	5 to 20
Garage	About 30

Tips for planning recessed lights

Keep lights about 2 to 3 ft from the walls. Closer than that makes bright scallops on the wall, unless you want to wash it on purpose.
Add task light where you work. Kitchen counters and sinks need light in front of you, not only overhead.
Check the joists before you mark holes, and shift the layout a few inches if a light lands on one.
Use IC-rated fixtures where insulation touches them, and airtight models in a ceiling below an attic.
Put the lights on a dimmer so one layout works for both bright tasks and a softer evening light.
The lumens calculator converts watts to lumens for bulbs. Adding new circuits and fixtures is a job for a licensed electrician, and must follow your local electrical code.

Frequently asked questions

How many recessed lights do I need?

Multiply the room area by the foot-candles for the room type to get lumens, then divide by the lumens of one fixture. Then lay them out evenly at about the ceiling height apart. A 12 × 12 ft bedroom with an 8 ft ceiling usually needs about 4 lights.

How far apart should recessed lights be?

A common rule is to space them about as far apart as the ceiling is high for general light, so about 8 ft apart under an 8 ft ceiling. For a more even wash, use half the ceiling height, about 4 ft apart.

How far from the wall should recessed lights be?

About half the spacing between the lights, which is often 2 to 4 ft. That keeps the light even at the edges of the room without harsh scallops on the walls.

What size recessed lights should I use?

4 in lights suit smaller rooms, hallways and accent lighting. 5 and 6 in lights give more light each and suit kitchens and larger rooms. Compare the lumens on the box, since output varies between models of the same size.

Can recessed lights touch insulation?

Only fixtures rated IC (insulation contact) can be covered by insulation. Non-IC fixtures need clearance around them set by the maker and code, so check the label and your local code.

Results are estimates for planning. Light output and beam spread vary by fixture, so check the box. See How We Calculate for the formulas we use.