Lighting
Recessed lighting spacing and placement
The grid on the ceiling is the last thing you should draw, not the first.
On this page (8 sections)
Short answer
Space downlights at the mounting height above the work plane multiplied by the fixture's spacing criterion, which is commonly 1.0 to 1.5. On an 8 ft (2.4 m) ceiling the work plane sits 5 ft 6 in (1.68 m) below the fixture, so 4 in (10 cm) downlights go 5 to 6 ft (1.5 to 1.8 m) apart for even ambient light, and about 4 ft (1.2 m) apart if you want a genuinely uniform wash. Start the first row at half the spacing from the wall, so 24 to 36 in (61 to 91 cm).
The numbers, at a glance
- Spacing, 8 ft ceiling, general
- 5 to 6 ft (1.5 to 1.8 m)
- Spacing, uniform wash
- about 4 ft (1.2 m)
- First row from the wall
- 24 to 36 in (61 to 91 cm)half the spacing
- Spacing criterion, typical downlight
- 1.0 to 1.5
- Beam angle, accent
- 15 to 25 degrees
- Beam angle, general
- 40 to 60 degrees
- Aiming angle for art
- 30 degrees from vertical
- Non-IC clearance to insulation
- 3 in (76 mm)NEC 410.116(B)
The spacing criterion, and where the folk rule comes from#
Every reputable downlight publishes a spacing criterion (SC), a dimensionless number from its photometric file. The rule is:
Maximum spacing = mounting height above the work plane x SC
Mounting height is not ceiling height. It is ceiling height minus the work plane, normally 30 in (76 cm) for a horizontal task or the floor for pure circulation, so an 8 ft (2.44 m) ceiling gives 5 ft 6 in (1.68 m).
- A typical 4 in (10 cm) LED downlight with a 40 to 60 degree beam has an SC of 1.0 to 1.1, giving 5 ft 6 in to 6 ft (1.68 to 1.8 m).
- A wide-distribution fixture at SC 1.5 stretches to 8 ft 3 in (2.5 m), but the light between fixtures visibly sags.
- For an even wash with no perceptible scalloping, work at 0.75 x mounting height, so 4 ft (1.2 m).
The folk rule "divide the ceiling height by two" gives 4 ft on an 8 ft ceiling. It is not wrong, it is the wash spacing applied to every room whether or not the room needs a wash, which is why so many houses have twice the downlights they need.
| Ceiling height | Mounting height above the 30 in work plane, and general spacing at SC 1.0 | Wash spacing (0.75 x) |
|---|---|---|
| 8 ft (2.44 m) | 5 ft 6 in (1.68 m) | 4 ft 2 in (1.27 m) |
| 9 ft (2.74 m) | 6 ft 6 in (1.98 m) | 4 ft 11 in (1.50 m) |
| 10 ft (3.05 m) | 7 ft 6 in (2.29 m) | 5 ft 8 in (1.73 m) |
| 12 ft (3.66 m) | 9 ft 6 in (2.90 m) | 7 ft 2 in (2.18 m) |
As the ceiling rises the fixtures spread out, but each must deliver more lumens to hold the same illuminance, since illuminance falls with the square of distance. See ceiling height and proportion.
The half-spacing rule at walls#
Start the first row at half the spacing from the wall: 2 ft 9 in (84 cm) at 5 ft 6 in spacing, 3 ft (91 cm) at 6 ft. A fixture at half-spacing covers the wall-side half of its footprint and meets its neighbour cleanly, so illuminance stays flat instead of dipping at the perimeter.
Where the wall carries upper cabinets, measure from the cabinet face. A run of 12 in (30 cm) deep uppers moves the effective wall 12 in into the room, so a can 30 in (76 cm) off the wall is really 18 in (46 cm) off the cabinet, lighting the door and shadowing the counter. See kitchen counter and cabinet heights.
Scallop or wash: 12 in versus 30 in#
- 12 in (30 cm) off the wall. The beam clips the wall steeply and leaves a bright crescent with a hard edge below. That is a scallop, and repeated it reads as a row of arches. Most people meet it after the ceiling is closed.
- 24 to 36 in (61 to 91 cm) off the wall. The beam covers the wall from picture height down and overlaps its neighbours. That is a wash, and a bright wall plane is the most effective way to make a room feel larger, as how to plan layered lighting explains.
For a wash, match spacing to offset: washers 30 in (76 cm) off the wall want 30 to 36 in (76 to 91 cm) centres.
Beam angles and the diameter you actually get#
Beam diameter = 2 x distance x tan(beam angle / 2)
| Beam angle | Use | Diameter at 5 ft 6 in | Diameter at 8 ft |
|---|---|---|---|
| 25 degrees | Art, a single object | 2 ft 5 in (74 cm) | 3 ft 7 in (109 cm) |
| 40 degrees | General, tighter rooms | 4 ft 0 in (122 cm) | 5 ft 10 in (178 cm) |
| 60 degrees | General ambient | 6 ft 4 in (193 cm) | 9 ft 3 in (282 cm) |
Beam angle is defined at 50 per cent of centre-beam intensity, so the lit patch is wider than the number implies. Two 60 degree fixtures at 5 ft 6 in centres overlap heavily, which is why the general spacing works.
Aiming at art: 30 degrees from vertical#
Aim accent fixtures at about 30 degrees from vertical. Steeper and you graze the picture, exaggerating canvas texture and throwing a frame shadow down the image. Shallower and the reflected beam bounces off glazing into the eye of a standing viewer.
A ceiling plan, drawn#
The 6 ft (1.8 m) row spacing sits at the criterion for an 8 ft ceiling. The 4 ft 8 in (1.42 m) column spacing is tighter because three fixtures fit the 14 ft (4.27 m) dimension more evenly than two. Uneven spacing between axes is invisible; uneven spacing within an axis is not.
The six-can mistake in a small kitchen#
A 10 x 10 ft (3 x 3 m) kitchen gets specified with six 4 in cans on a 3 x 2 grid. Two things go wrong.
Geometry: six fixtures across a 10 ft dimension means centres at roughly 3 ft 4 in (1 m), 40 per cent under the spacing criterion, and the ceiling becomes a colander.
Position: deduct the cabinet runs and a 10 x 10 kitchen has only about 45 sq ft (4.2 sq m) of open floor. Most of the ceiling is over 24 in (61 cm) deep counters, and a downlight over a counter puts light behind you when you stand at it, so your own shoulders shadow the work surface.
Four cans on a 5 x 5 ft (1.5 x 1.5 m) grid, positioned so the beams land on the front of the counters, plus continuous undercabinet strips, is the correct 10 x 10 kitchen scheme.
IC rating, insulation and apertures#
Type IC luminaires may touch thermal insulation. Non-Type IC may not: NEC 410.116(B) requires 3 in (76 mm) clearance to insulation and 410.116(A)(1) requires 0.5 in (13 mm) from combustible material except at the point of support. In a ceiling forming part of the thermal envelope, IRC energy provisions also require the luminaire to be sealed against air leakage, so specify ICAT (insulation contact, airtight). A can that is neither is two problems: a fire risk if someone insulates over it later, and a permanent hole into the loft.
| Nominal aperture | Typical cut-out | Typical output | Where it belongs |
|---|---|---|---|
| 2 in (5 cm) | 2.4 to 2.6 in (61 to 66 mm) | 350 to 600 lm | Accent, niches, tight ceilings |
| 3 in (7.5 cm) | 3.2 to 3.5 in (81 to 89 mm) | 500 to 800 lm | Discreet ambient, halls |
| 4 in (10 cm) | 4.1 to 4.5 in (104 to 114 mm) | 650 to 1,100 lm | The residential default |
| 6 in (15 cm) | 6.4 to 6.8 in (163 to 173 mm) | 900 to 1,600 lm | High ceilings, large open plans |
Cut-outs vary by manufacturer and are not interchangeable between brands. Cut to the paper template in the box, not the nominal name, and check housing depth against joist depth before ordering.
The order to lay out a ceiling in#
- Mark the fixed things first. Counter edges, the island, the art wall, the reading chair, the vanity.
- Place accent and task fixtures on those positions, 24 to 30 in (61 to 76 cm) off walls and cabinet faces.
- Only now draw the ambient grid in the ceiling that is left, setting spacing from the criterion rather than the fixture count.
- Check no fixture lands over a seat back or a bed head. A downlight above a pillow is a permanent irritation.
- Check joists, ducts and the loft hatch. Joists at 16 in (41 cm) centres leave about 14.5 in (37 cm) clear, fine for anything up to 6 in.
- Total the lumens against the room target from how many lumens a room needs. If the grid overshoots, keep the spacing and drop to lower-output fixtures rather than fewer holes.
Frequently asked questions#
How far apart should recessed lights be on an 8 foot ceiling?
5 to 6 ft (1.5 to 1.8 m) for 4 in (10 cm) downlights giving general ambient light. The calculation is mounting height above the work plane, which is 8 ft minus a 30 in (76 cm) work plane, so 5 ft 6 in (1.68 m), multiplied by a spacing criterion of about 1.0. If you want an even wash with no visible falloff between fixtures, tighten to about 4 ft (1.2 m).
How far from the wall should recessed lights be?
Half the spacing, which is typically 24 to 36 in (61 to 91 cm). At 12 in (30 cm) you get a hard scallop of light on the wall and a dark ceiling behind it. At 30 in (76 cm) the beam covers the wall evenly from picture height down. Where there are upper cabinets, measure from the cabinet face rather than the wall.
How many recessed lights do I need in a 10x10 kitchen?
Four, not six. A 10 x 10 ft (3 x 3 m) kitchen has about 45 sq ft (4.2 sq m) of open floor once the cabinet runs are deducted, and six cans at 5 ft spacing will not fit that footprint without dropping to roughly 3 ft 4 in (1 m) centres. Four cans plus undercabinet task strips give better light on the counter and a ceiling that does not look perforated.
What is the spacing criterion on a downlight spec sheet?
A number, usually between 0.7 and 1.5, published by the manufacturer from the fixture's photometric file. Multiply it by the mounting height above the work plane to get the maximum spacing that still gives acceptable uniformity. A narrow-beam accent fixture may have a spacing criterion of 0.7; a wide flood may be 1.5. It is the only spacing figure that is specific to the fixture you actually bought.
What beam angle should I use for recessed lights?
40 to 60 degrees for general room lighting, 25 to 38 degrees for a defined pool over an island or a table, 15 to 25 degrees for accenting art or an object. Beam diameter is 2 x distance x tan(half the beam angle), so a 40 degree lamp 5 ft 6 in (1.68 m) above a counter covers about 4 ft (1.2 m) of it.
Can recessed lights touch insulation?
Only if the fixture is IC-rated. A non-IC luminaire must keep 3 in (76 mm) clear of thermal insulation and 0.5 in (13 mm) from combustible materials other than at the point of support, per NEC 410.116. In an insulated ceiling you want IC-rated and airtight, usually marked ICAT, because IRC energy provisions also require the luminaire to be sealed against air leakage.
Should recessed lights be centred in the room or over the furniture?
Over what you care about, with the grid as a fallback. A ceiling grid centred on the room is easy to draw and often lands a fixture over the middle of a sofa, where it lights the top of your head. Position for the counter edge, the art wall and the reading chair first, then even out the leftovers so the spacing never exceeds the criterion.
Sources and standards referenced#
- The Lighting Handbook, 10th Edition Illuminating Engineering Societyspacing criterion, uniformity, zonal cavity method
- ANSI/IES RP-11, Recommended Practice: Lighting Interior and Exterior Residential Environments Illuminating Engineering Societyresidential downlight placement
- NFPA 70, National Electrical Code, Article 410 Part XII National Fire Protection Association410.116 clearance and installation of recessed luminaires
- International Residential Code (IRC) 2021 International Code CouncilN1102.4.5, recessed luminaires in the thermal envelope must be IC-rated and sealed
- UL 1598, Standard for Luminaires Underwriters LaboratoriesType IC and non-Type IC classification
We cite published codes, industry planning guidelines and manufacturer specifications. Where a figure is our own recommendation rather than a published standard, the text says so. See how we measure.