Recessed Lighting Spacing Calculator

Divide each room dimension by the spacing you want, then add one for the can at the start of the row. The calculator does this for the length and the width, then multiplies the two counts for the total. A 16 by 12 ft room with an 8 ft ceiling and a 2 ft wall offset works out to a 4 by 3 grid, or 12 cans.

The common rule of thumb is to space recessed lights apart by half the ceiling height. An 8 ft ceiling gives 4 ft spacing, a 9 ft ceiling gives 4.5 ft, and a 10 ft ceiling gives 5 ft. That distance is the maximum for even general lighting, so the calculator tightens the actual spacing as needed to fit your room evenly.

Place the outer row of cans about 1.5 to 3 ft from the wall. A popular choice is half the spacing distance, which keeps the ceiling evenly lit without bright scallops down the walls. Set the wall offset field to the distance you prefer and the layout adjusts the fixture count and spacing to match.

Each direction is filled on its own so the cans land evenly along that wall. A room that is 17 ft one way and 12 ft the other rarely splits into the same number of equal gaps, so you might see 3.25 ft spacing one way and 4 ft the other. Both still stay at or below the maximum set by the ceiling-height rule.

The half-the-ceiling-height rule sets the spacing for general ambient light. Over task zones like a kitchen island, a reading chair, or a workbench, plan the cans closer together than the result or add under-cabinet and pendant lighting. Treat this grid as the baseline for even, room-wide coverage.

The layout is based on room geometry and spacing, not on a specific housing size, so it works for 4, 5, and 6 in cans and most LED retrofit trims. Match the trim's beam angle and brightness to the room, since a narrow beam or a tall ceiling can call for closer spacing than the general rule gives.