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Recessed Lighting Calculator

Recessed light spacing is half the ceiling height, so an 8 ft ceiling puts cans 4 ft apart and a 14 by 12 ft room takes 12 lights.

Units
Room length
ft
in
Room width
ft
in
Ceiling
ft

IES range 10 to 20 footcandles.

lm/sq ft

Middle of the range; raise it for older eyes.

lm

Use the number on the box.

How many lights
Distance from the wall

Recessed lights for this living room

12lights

A 4 by 3 grid of 900 lm lights, 4 ft or less apart.

The spacing rule sets the count here: 3 lights would reach the brightness target, but 12 keep the spread even. Put them on a dimmer.

14 ft12 ft3 ft 6 in4 ft
Spacing, length direction
3 ft 6 in
Spacing, width direction
4 ft
First light from the wall
1 ft 9 in
Light delivered
10,800lm
Light level reached
64.3 lm/sq ft
Lights for lumens only
3
The math

  1. Room area

    14 ft × 12 ft = 168 sq ft

  2. Lumens needed

    168 sq ft × 15 lm/sq ft = 2,520 lm

  3. Lights for brightness

    2,520 lm ÷ 900 lm, rounded up = 3 lights

  4. Maximum spacing

    8 ft ceiling × 0.5 = 4 ft

  5. Lights for even spacing

    4 along the length × 3 along the width, each gap at most 4 ft = 12 lights

  6. Wall distance

    3 ft 6 in spacing ÷ 2 = 1 ft 9 in

Spacing rule: distance between recessed lights is half the ceiling height. Light targets are the middle of the IES residential ranges.
Turn the breaker off before you cut in a housing, use IC-rated housings wherever insulation touches the fixture, and keep the circuit within its breaker rating. Most places require a permit and inspection for new circuits, and many only let a licensed electrician or the homeowner of a single-family house do the work. Turn the breaker off and test the wires dead before you touch them, and have a licensed electrician check anything you are unsure about.

Recessed light spacing is half the ceiling height: an 8 ft ceiling puts the lights 4 ft apart, so a 14 by 12 ft living room takes a grid of 4 by 3, which is 12 lights. The calculator adds the second half of the job, brightness, by comparing the lights that spacing needs with the lumens the room asks for, and draws the layout from the real result.

How recessed light spacing and count are calculated

Two rules set the number of can lights, and the larger one wins.

  1. Even spread. Lighting guides from Bees Lighting and Cans and Fans give the same half-height rule: distance between lights = ceiling height ÷ 2, and no more than about 6 ft on tall ceilings. Fewer lights than the rule needs leaves dark patches and scallops on the walls.
  2. Enough light. The room area in square feet times the footcandles for the room gives the lumens needed, and dividing by the lumens of one fixture gives the count.

Lights = larger of (rows × columns at ceiling height ÷ 2) and (area × footcandles ÷ lumens per light)

Rows and columns come from dividing each room side by the maximum spacing and rounding up, so the lights end up evenly spread and never farther apart than the rule allows. By default the first light sits half a spacing from the wall, which makes the space between a light and the wall half the space between two lights.

Worked example: living room, 14 by 12 ft, 8 ft ceiling

With the defaults (6 in LED, 900 lm, living room at 15 lm per sq ft):

  • Area: 14 ft × 12 ft = 168 sq ft; lumens needed: 168 × 15 = 2,520 lm, which is only 3 lights of 900 lm.
  • Maximum spacing: 8 ft × 0.5 = 4 ft. Along 14 ft that is 4 lights (3.5 ft apart), along 12 ft it is 3 lights (4 ft apart): 12 lights.
  • The wall distance is 1.75 ft on the long side and 2 ft on the short side.

Twelve 900 lm lights give 10,800 lm, about 64 lm per sq ft, four times the living room target. That is normal for the spacing rule and the reason recessed lights go on a dimmer. Switch "How many lights" to Lumens only and the count drops to 4 lights, 7 ft by 6 ft apart, which is wider than the 4 ft rule, so expect uneven light.

Recessed lighting layout by ceiling height

Ceiling heightMaximum spacingLights in 14 × 12 ft
8 ft4 ft12
9 ft4.5 ft12
10 ft5 ft9
12 ft6 ft6

Taller ceilings need fewer lights, but each light must be brighter and have a narrower beam, so choose higher lumens per fixture when you raise the ceiling height.

Recessed lighting for a kitchen

The IES range for general kitchen light is 20 to 50 footcandles and 50 to 100 for cooking and prep; the calculator uses the middle of each. A 14 by 12 ft kitchen at 35 lm per sq ft needs 5,880 lm, which is 7 lights of 900 lm or 9 lights of 700 lm (4 in LED), still under the 12 lights the 8 ft ceiling spacing asks for. Choose Kitchen, cooking and prep and the target rises to 75 lm per sq ft, or 12,600 lm: 14 lights of 900 lm, which lands on a 4 by 4 grid of 16. Keep the cans over counters and the sink, not over where you stand.

Recessed lighting with a ceiling fan

Tick Ceiling fan in the center and enter the blade span. Lights stay at least 24 in from the blades (Bees Lighting), so the keep-out circle has a radius of half the span plus 24 in: 52 in ÷ 2 + 24 in = 50 in, about 4.2 ft. In a 16 by 14 ft room at 8 ft the grid is 4 by 4; the fan zone takes out 4 positions and the plan keeps 12 lights (10,800 lm against 3,360 lm needed).

Recessed lighting on a sloped or vaulted ceiling

Choose Sloped or vaulted and enter the low and high wall heights. Spacing uses the average height, and all distances are measured on the floor plan, not along the slope. A ceiling running from 8 ft to 12 ft averages 10 ft, so the same 14 by 12 ft room takes 9 lights. Buy housings made for sloped ceilings (they exist for insulated and uninsulated vaults) so the beam points at the floor.

Wall distance, fixture size and LED lumens

Wall wash puts the first row 18 in from the wall; guides quote 12 to 18 in for this, and 2 to 3 ft for standard placement. It adds lights: 16 instead of 12 for the 14 by 12 ft room. Typical LED cans give about 600 to 800 lm at 4 in and 800 to 1,000 lm at 6 in, but use the number on your box. Housings touching insulation must be IC rated; non-IC housings need 3 in of clearance.

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