How this calculator works
Recessed lights look even when the gaps between them are equal and the lights nearest the walls are closer to the wall than to each other. A grid layout starts with the number of lights across and along, then spreads them evenly over the room minus the wall gap at each end. With three lights across a 4 m room and a 75 cm gap, the two spaces between the lights take the remaining 2.5 m, so the lights sit 1.25 m apart. The table gives the position of each light, measured from one corner, which is what an installer needs to mark out the ceiling.
Formula
spacing across = (room width - 2 x wall gap) / (lights across - 1). spacing along = (room length - 2 x wall gap) / (lights along - 1). number of lights = rows x columns. position = wall gap + index x spacing.
Worked example
A 5 m by 4 m room with three lights across, two along and a 75 cm gap has 6 lights. The spacing across is (4 - 1.5) / 2 = 1.25 m and along is (5 - 1.5) / 1 = 3.5 m. The first light sits 0.75 m from two walls, and the second row sits 4.25 m along.
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Frequently asked questions
How far apart should recessed lights be?
A common rule is to space them at about the height of the ceiling above the floor to twice that height. In a 2.4 m room that means roughly 1.2 to 2.4 m apart, which usually gives even light without overlapping beams.
How far from the wall should the first light be?
Close to half the spacing between lights keeps the wall wash even. The edge gap here defaults to 75 cm, which suits a 2.4 m ceiling and a standard downlight.
What about task areas such as a counter or a desk?
Grids light a room evenly but put light where you do not always need it. Add extra lights over counters and desks and reduce the grid density, or use a second switched circuit so the task lights can run alone.
Why can I only use rows and columns?
A rectangular grid is the layout most ceilings can take evenly. If the room is L-shaped, split it into two rectangles and run the calculator for each one.