Half the spacing between fittings. With 4 ft spacing on an 8 ft ceiling, that is 2 ft from the wall. On a 10 ft ceiling with 5 ft spacing, it is 2.5 ft.
That is the rule. The reason behind it is what tells you when to break it.
The walls are what make a room look bright
People judge how bright a room is mostly by its vertical surfaces, not its floor. Walls occupy far more of your field of view than the floor does, and a lit wall bounces light back into the space.
Put the outer fittings 2 ft from the wall and the edge of each cone falls on the wall itself, washing it from top to bottom. Push them out to 4 or 5 ft and every cone lands on the floor. The walls go dark, the room reads as gloomy, and the usual response — adding more fittings in the middle — makes the ceiling spottier without fixing anything.
Why half the spacing, specifically
A fitting in the middle of the grid lights the area around it in every direction, sharing each side with a neighbor. A fitting at the edge has a neighbor on one side and a wall on the other, so it only has to cover half as much distance outward.
Half the spacing puts every point on the ceiling the same distance from a light source — which is what makes the light even rather than banded.
| Ceiling | Spacing | From wall |
|---|---|---|
| 8 ft | 4 ft | 2 ft |
| 9 ft | 4.5 ft | 2.25 ft |
| 10 ft | 5 ft | 2.5 ft |
| 12 ft | 6 ft | 3 ft |
When to move them closer
Tall cabinets, bookcases or a fireplace on that wall. Go to 12–18 inches so the light falls down the face of the cabinetry rather than onto the floor in front of it. Any closer and the top of the unit casts a hard shadow.
Artwork you want lit. Around 18–24 inches for a standard ceiling, and use an adjustable or gimbal fitting aimed at the center of the piece.
Deliberate wall washing. Some fittings are designed for it, with an asymmetric beam that throws light sideways. These sit 12–18 inches out and produce an even graded wash rather than a scalloped arc.
When to move them further
A sloped ceiling. Measure the offset from the wall the fitting is near, and check the beam is not aimed into the slope.
A wall with nothing on it, in a room where floor light matters more — a workshop or a garage. Even then, do not exceed the spacing itself.
The mistake that produces scallops
Standard downlights near a wall produce arcs on the wall — bright at the top, fading downward, curved at the edges. Space them at the grid interval and those arcs read as a rhythmic pattern, which looks deliberate.
Space them irregularly and it looks like an error. This is why the wall offset should be the same on every wall in a room even when that means the middle spacing is slightly uneven. Your eye reads the edges as a border; it does not audit the middle.
What about the corners
Corner fittings sit at the offset distance from both walls — 2 ft in and 2 ft across on an 8 ft ceiling. Do not aim a fitting into the corner itself. Corners are naturally darker and trying to fix that with a dedicated downlight produces a hot spot rather than an evenly lit corner.
If a dark corner genuinely bothers you, a floor lamp or an uplighter does the job far better, because it lights the corner from below and behind rather than from directly above.
Working out the full layout
The offset is one half of a layout. The other half is the spacing itself and how many fittings the room takes, both covered in recessed light spacing and worked through for a square room in how many recessed lights in a 12×12.
For total output across the whole grid, the room lighting calculator gives the lumens and divides them across the fittings.