Recessed Lighting Spacing and Layout

From target illuminance to fixture count

Multiply the target illuminance by the room area, then divide by the utilization and light-loss factors and the rated lumens per fixture. Round the result up. Use fixture output after optical losses and factors appropriate to that lumen rating.

Typical residential targets are modest. Kitchens, workshops and task areas need considerably more than a hallway or bedroom.

Arranging them

Spread the fixtures so the spacing is even in both directions and the distance from the wall is about half the spacing. That puts light on the walls instead of leaving dark edges.

A common rule of thumb is that the centre-to-centre spacing should not exceed half the ceiling height. Higher ceilings tolerate wider spacing.

Frequently asked

What illuminance should I aim for?

It depends on the room. Living spaces are commonly in the 10 to 20 foot-candle range, while kitchens and workspaces are set considerably higher.

Does the calculator account for wall colour and daylight?

Only if you enter them. Coefficient of utilization and light-loss factor default to 1, which assumes every lumen reaches the work plane and nothing is lost. That result is an upper bound. Dark surfaces and depreciation belong in a utilization factor often around 0.5 to 0.7 and a light-loss factor often around 0.7 to 0.85.

Is recessed lighting spacing a code requirement?

No. It is a design calculation, not an electrical code rule. The electrical requirements concern the wiring and the fixtures, not the layout.

Related calculators

• Recessed Lighting Calculator
• Box Fill Calculator
• Quick reference (PDF)