How far apart should recessed lights be?

Half the ceiling height. Eight-foot ceilings take lights four feet apart, ten-foot ceilings five. The rule works because a downlight throws a cone: at half the height the cones overlap at working level, and further apart they leave scallops of dark floor between them.

How far from the wall should the first light be?

Half the spacing — two feet on an eight-foot ceiling. Closer than that and the fitting washes the wall instead of the room; further and the perimeter goes dark, which is where the furniture is.

Why does this give two numbers?

Because spacing and brightness are separate constraints and either can be the binding one. A large room with bright fittings needs more holes than the light level demands, purely so the pattern is even. A small dark room needs more light than the grid provides. Fitting the larger of the two satisfies both.

What is a footcandle?

One lumen falling on one square foot. It is the unit the recommendations are written in: about 10 for a hallway, 20 for a living room, 30 for a kitchen and 50 over a worktop. Lumens describe the bulb; footcandles describe what reaches the surface, which is what you actually see by.

Recessed Light Calculator

With room length 16 ft, room width 12 ft, ceiling height 8 ft, lumens per fitting 800 lm, recessed light comes to 12 lights — lights to fit. It is reached in 6 steps, the last of which is max(12, 7), and each one is printed on the page with its numbers filled in. The formula is the one published by Illuminating Engineering Society, not an approximation fitted to it.

How many recessed lights a room needs and how far apart, from the ceiling height and the light level the room is for.

Formula and sources checked 16 August 2026 · How we check

Room length 16 ft, Room width 12 ft, Ceiling height 8 ft, Room and light level Living room or bedroom — 20 fc

12 lights

Lights to fit for the example below. Editing a field recomputes the calculator below; this figure holds the answer the page was loaded with.

It is written into the HTML rather than drawn by a script, so a search engine reading this page without running JavaScript still finds an answer.

Room lengthRoom widthCeiling heightRoom and light levelLumens per fittinglmA 4 in LED downlight is typically 650–900 lumens; a 6 in one 900–1,200.

Lights to fit

12 lights

Ceiling area: 16 * 12192 sq ft
Spacing, ceiling height ÷ 2: 8 / 24 ft
Distance from the wall: 4 / 22 ft
Lights by the spacing rule: 4 * 312 lights
Lights for that level: ceil((192 * 20) / (800 * 0.7))7 lights
Lights to fit: max(12, 7)12 lights

Ask about this in the chat

Worked example

A 16 × 12 ft living room with an 8 ft ceiling spaces lights 4 ft apart, 2 ft off the wall: four along the length by three across is 12. The 20 footcandle target needs only 7 fittings of 800 lumens, so the spacing rule governs here — take whichever number is larger.

How to work it out yourself

1.Halve the ceiling height. That is the spacing between lights, and half of it is the distance from the wall.
2.Divide the room dimensions by that spacing and round to whole lights each way; multiply for the grid.
3.Separately: multiply area by the footcandles the room is for, and divide by the lumens per fitting allowing about 30% loss.
4.Fit whichever count is higher. Spacing governs a big room with bright fittings; light level governs a small room with dim ones.

The formula

Ceiling area16 * 12
Spacing, ceiling height ÷ 28 / 2
Distance from the wall4 / 2
Lights by the spacing rule4 * 3
Lights for that levelceil((192 * 20) / (800 * 0.7))
Lights to fitmax(12, 7)

Source: Illuminating Engineering Society — recommended illuminance, US Department of Energy — LED lighting

Questions people actually ask

How far apart should recessed lights be?: Half the ceiling height. Eight-foot ceilings take lights four feet apart, ten-foot ceilings five. The rule works because a downlight throws a cone: at half the height the cones overlap at working level, and further apart they leave scallops of dark floor between them.
How far from the wall should the first light be?: Half the spacing — two feet on an eight-foot ceiling. Closer than that and the fitting washes the wall instead of the room; further and the perimeter goes dark, which is where the furniture is.
Why does this give two numbers?: Because spacing and brightness are separate constraints and either can be the binding one. A large room with bright fittings needs more holes than the light level demands, purely so the pattern is even. A small dark room needs more light than the grid provides. Fitting the larger of the two satisfies both.
What is a footcandle?: One lumen falling on one square foot. It is the unit the recommendations are written in: about 10 for a hallway, 20 for a living room, 30 for a kitchen and 50 over a worktop. Lumens describe the bulb; footcandles describe what reaches the surface, which is what you actually see by.

Put this calculator on your site

Free, no attribution required beyond the link.

<iframe src="https://rulecalculators.com/embed/recessed-lighting" width="100%" height="420" style="border:1px solid #e7e4de;border-radius:12px" title="Recessed Light Calculator"></iframe>

Did this answer your question?