Space downlights at roughly half your ceiling height apart, and half that distance from the walls. With a standard UK ceiling of 2.4m, that means about 1.2m between fittings and 60cm from the walls. For the count, multiply the floor area by the room's target light level — around 250 lux for a kitchen, 150 for a living room, 100 for a hallway — and divide by one downlight's output (a typical LED downlight gives about 600 lumens). A 12m² kitchen lands on five or six.
Downlights are the only light fitting people buy by the dozen, and the advice on how many swings between "one per square metre" and "as few as you can get away with". Neither is a plan. The honest answer is two small sums — one for spacing, one for quantity — followed by ten minutes with a floor plan, moving the fittings to where the light actually has a job to do. This guide walks through both sums, with worked figures for the rooms UK downlights usually end up in.
What is the formula for spacing downlights?
Divide the ceiling height by two. That is the distance to leave between downlights. A standard 2.4m UK ceiling gives a spacing of about 1.2m; a 2.7m Victorian ceiling gives about 1.35m. The logic is simple: a downlight throws a cone of light that widens as it falls, and at half-height spacing the cones from neighbouring fittings overlap at the height where you live and work, so the room reads as evenly lit rather than as a row of bright pools with dark bands between them.
It is a rule of thumb, not a regulation. Push the fittings a little further apart and the light gets moodier, with soft pools rather than an even wash — often exactly right for a living room or bedroom. Squeeze them closer and the light flattens out — useful over a kitchen worktop, wasteful in the middle of a room. Start at half the ceiling height and adjust with intent.
How many downlights do I need for my room?
Spacing tells you the pattern; lumens tell you the number. Multiply the room's floor area in square metres by a target light level in lux, and you have the total lumens the room needs from its general lighting. Then divide by the output of one downlight. The Valtari we stock puts out 600 lumens, which makes it a convenient unit of account; the table below uses it.
| Room | Target level | Example room | Lumens needed | 600lm downlights |
|---|---|---|---|---|
| Kitchen | 250–300 lux | 12m² | 3,000–3,600 | 5–6 |
| Bathroom | 150–200 lux | 6m² | 900–1,200 | 2 |
| Living room | 100–150 lux | 16m² | 1,600–2,400 | 3–4 |
| Bedroom | 100–150 lux | 12m² | 1,200–1,800 | 2–3 |
| Hallway | 100 lux | 5m² | 500 | 1–2 |
Two caveats make the table honest. First, these are targets for the general layer only — a kitchen still wants task light where you chop, and a living room is far nicer when lamps and wall lights carry the evening and the downlights barely feature. Second, dark walls and floors swallow light, so a room with charcoal cabinetry or a deep green wall sits at the top of each range. If you want the arithmetic behind lux and lumens, our lumens guide unpacks it.
Valtari Slim Fire-Rated Downlight · 600 lumens
A known output makes the sums easy: 7W and 600 lumens per fitting, IP65, fire-rated for 90 minutes, and just 32mm deep in a 68mm cut-out — with a switch to set the colour temperature between 2700K and 6000K.
How far from the walls should downlights sit?
Half the spacing. If your fittings are 1.2m apart, keep the outer row about 60cm from the walls. The reasoning is the same cone geometry: the wall receives light from one side only, so a fitting placed a full spacing away leaves the room's edges dim, which is precisely where worktops, wardrobes and bookshelves live.
Kitchens earn one refinement. Where downlights serve a worktop, place them over its front edge rather than in the centre of the walkway behind you — light from behind puts your own shadow on the chopping board. Over the run of units, that usually means the outer row sits closer to the wall than the half-spacing rule suggests, and that is fine: here the downlight's job is the worktop, not the floor.
Should downlights be laid out in a grid at all?
Not blindly. The grid is a starting pattern for even general light, but the better question for each fitting is: what is this one for? Kitchens want them over worktops, hob and island. Bathrooms want one over the shower and honest light at the mirror — which is really a wall-light job in zone 2, with the zones deciding the ratings: at least IPX4 in zones 1 and 2, which an IP65 downlight comfortably exceeds. Living rooms and bedrooms often want downlights only at the edges — washing shelves, curtains or artwork — leaving the centre of the ceiling to a pendant and the atmosphere to lamps.
Planned that way, most rooms need fewer downlights than the forums suggest, and every one of them earns its hole in the ceiling. A ceiling with thirty holes in it is not a lighting scheme; it is a colander with a standing charge.
Which downlights make the plan easiest?
Two things simplify a downlight scheme: a known lumen output, and a fitting you will not mind seeing repeated a dozen times. An integrated fitting like the Valtari states its output on the box, so the table above works as written. A GU10 fitting like the Kanto takes whatever bulb you choose — so the output, beam and colour temperature are decided by the bulb, and you should run the sums with the lumen figure printed on the bulb you actually intend to fit.
Kanto Trimless Plaster-In Downlight · GU10
Skimmed flush into the plaster, so the ceiling shows an aperture of light and no bezel at all. IP65 and fire-rated, in fixed (£17) and tiltable (£22) versions that share the same face — the tiltable is the one for washing art or shelves.
Whichever you choose, check the fire rating against your ceiling — our fire-rated guide explains when it is required — and put the circuit on a dimmer, because a scheme sized for a bright Tuesday evening of homework should also do a quiet Friday night at 30 per cent.
Do I need an electrician to fit downlights?
For new downlight positions, yes — new holes mean new wiring, and a registered electrician will design the circuit, check the fire rating against the ceiling and certify the work. In England, work in the special locations around a bath or shower, new circuits and consumer-unit changes are notifiable under Part P; adding lights to an existing circuit in a kitchen or living room is not notifiable in itself, but it still needs to be done competently and to BS 7671. Wales, Scotland and Northern Ireland each have their own rules. A like-for-like swap of an existing fitting, with the circuit isolated, is the only downlight job that sensibly stays DIY.
