Too few downlights and you get dark corners and pools of shadow. Too many and your ceiling looks like an airport runway and your electricity bill agrees. Getting the number right isn’t guesswork, though. A couple of simple rules will get you very close, and this guide walks through them with worked examples.
The spacing rule that does most of the work
The quickest starting point used across the trade is to divide your ceiling height by two. That gives you the distance to leave between downlights.
So for a standard 2.4m ceiling, you’d space downlights about 1.2m apart. For a taller 3m ceiling, roughly 1.5m apart. The taller the ceiling, the further the light spreads before it lands, so the further apart the fittings can sit.
One more rule keeps the edges of the room even: set the outer row about 0.6m from the walls. Any closer and you get scalloped bright patches up the wall. Any further and the room edges fall into shadow.
A worked example
Take a 4m by 5m living room with a 2.4m ceiling, so 1.2m spacing.
- Along the 4m wall: 4 ÷ 1.2 is about 3 fittings.
- Along the 5m wall: 5 ÷ 1.2 is about 4 fittings.
- 3 × 4 gives a 12-downlight grid.
Twelve is fine for bright, even coverage, but a living room rarely wants to be floodlit. This is where the second question comes in: how bright does the room actually need to be?
How bright? Think in lumens per square metre
Brightness is measured in lumens, not watts. A rough target for how much light a room wants, per square metre of floor, looks like this:
| Room | Target brightness |
|---|---|
| Living room, bedroom | 100 to 150 lumens per m² |
| Kitchen, home office, bathroom | 200 to 300 lumens per m² |
| Hallway, utility | 150 to 200 lumens per m² |
Multiply your floor area by the target to get total lumens, then divide by the output of one downlight (a typical LED downlight gives 400 to 600 lumens). That tells you how many you need to hit the brightness, which you can sanity-check against the spacing grid. For relaxed rooms, lean on fewer downlights and add lamps. For working rooms, use the fuller grid.
Beam angle changes the spacing
A downlight’s beam angle decides how wide its light spreads. Most home downlights are 36 to 60 degrees.
- Narrow beam (36 to 40 degrees): a tighter, more focused pool of light. Good for accenting, but space them closer or you’ll see gaps.
- Wide beam (60 degrees): a softer, broader spread that covers more floor per fitting, so you can space them a touch further apart.
If you’re lighting a worktop or a reading corner, a narrower beam puts light where you want it. For general room fill, a wider beam gives more even coverage with fewer fittings.
Don’t forget the ceiling void and fire rating
Two practical checks before you buy:
- Clearance above the ceiling. Standard downlights need roughly 70 to 100mm of space above the plasterboard for the fitting body. If your void is shallow, low-profile downlights need as little as 25mm.
- Fire-rated fittings. Wherever a downlight cuts through a ceiling with a room or loft above, it needs to be fire-rated, so it restores the fire resistance that the hole removes. They cost only a little more, so plenty of people fit them throughout for simplicity. In bathrooms, they also need the right IP rating for the zone, which our bathroom zones guide explains.
Put it on a dimmer, and layer it
Even the best downlight grid is happier on a dimmer, so one room can be bright for cleaning and soft for an evening. And downlights alone rarely make a room feel finished. Adding lamps, pendants or under-cabinet strip is what turns flat, even light into something with depth, which is the heart of our kitchen lighting guide. Pair the plan with the right colour temperature and you’re most of the way there.
Let us mark up your plan
Bring a floorplan to any Luxwell showroom and a lighting designer will plot your downlight positions, spacing and beam angles for free, then show you the fittings switched on so you can see the effect before you commit. Details are on the contact page.
