How Many Downlights Do I Need? Spacing and Layout Guide
Downlight layouts go wrong in two directions and both are expensive to fix once the ceiling is closed. Too few and you get pools of light with dark gaps between them; too many and you get a ceiling that looks like an airport runway, plus a lighting bill and a lot of holes in your insulation.
The rule of thumb you will hear most often — space them at ceiling height divided by two — is a starting point, not an answer, because it takes no account of how many lumens each fitting produces. Here is the calculation that does.
The calculation
Three steps.
1. Find your room area in square metres. Length × width.
2. Multiply by the lumens per m² that room type needs (table below). That gives you total lumens required.
3. Divide by the lumen output of the downlight you have chosen. That is your number of fittings.
Worked example. A 4 m × 5 m living room is 20 m². Living rooms want roughly 300 lm/m², so 20 × 300 = 6,000 lumens. Using a 10W downlight at 900 lm, 6,000 ÷ 900 = 6.7, so seven downlights.
Tip: Always round up, and always put the result on a dimmer. Lighting that is slightly too bright and dimmable is a solved problem. Lighting that is too dim is a ceiling repair.
Lumens by room
| Room | Lumens per m² | 20 m² room needs | Fittings at 900 lm |
|---|---|---|---|
| Bedroom | 150–200 lm/m² | 3,000–4,000 lm | 4 |
| Living / lounge | 250–350 lm/m² | 5,000–7,000 lm | 6–8 |
| Kitchen (general) | 400–500 lm/m² | 8,000–10,000 lm | 9–11 |
| Kitchen benchtop (task) | 600–800 lm/m² | — | Add strip or pendants |
| Bathroom | 400–500 lm/m² | 8,000–10,000 lm | 9–11 |
| Hallway | 150–200 lm/m² | 3,000–4,000 lm | 4 |
| Home office / study | 400–500 lm/m² | 8,000–10,000 lm | 9–11 |
| Garage / workshop | 300–400 lm/m² | 6,000–8,000 lm | 7–9 |
| Laundry | 300–400 lm/m² | 6,000–8,000 lm | 7–9 |
These are targets for general ambient light. Task areas — a kitchen bench, a vanity mirror, a desk — need their own dedicated light on top, not more ceiling downlights. A downlight directly behind you casts your own shadow onto the work surface, which is why kitchens get under-cabinet lighting and bathrooms get lighting beside the mirror rather than above it.
Spacing and layout
Once you know the number, the layout follows two rules.
Spacing between fittings
The old rule — ceiling height ÷ 2 — gives 1.2 m on a 2.4 m ceiling and 1.35 m on a 2.7 m ceiling. Treat that as the maximum for a 90 mm, 900 lm fitting. Wider and you will see scalloping between the pools of light.
| Ceiling height | Typical spacing | Distance from wall |
|---|---|---|
| 2,400 mm | 1,100–1,300 mm | 600–750 mm |
| 2,700 mm | 1,200–1,400 mm | 700–800 mm |
| 3,000 mm | 1,400–1,600 mm | 750–900 mm |
Distance from the wall
Roughly 600–800 mm from the wall, or about half your fitting-to-fitting spacing. Closer than that and you wash the wall with a hot spot; further and the room's edges go dark and the room reads smaller than it is.
Set out from the room, not from the ceiling joists
Mark the grid from the walls so it is symmetrical in the room, then adjust individual fittings to miss joists — not the other way around. An asymmetric grid is visible from across the room; a fitting 80 mm off its theoretical position is not.
Also plan around the things that will be there later: a ceiling fan in the middle of a living room, a rangehood, a robe door swing, a pendant over the dining table. A downlight directly beside a ceiling fan blade produces a strobing shadow every time the fan runs.
Beam angle and cut-out size
Beam angle is how wide the light spreads. Most general-purpose downlights are 60°–100°:
- 60° — a tighter, more defined pool. Better for higher ceilings and for a deliberate, layered look. The Martec Rex Gimbal is 60°.
- 100° — broad, even wash. Better for standard ceilings and general lighting, and more forgiving of imperfect spacing. The Titan II and Zone are 100°.
Cut-out size is the hole diameter. 90 mm is the Australian standard and what you should specify unless you have a reason not to — it is the size every replacement fitting is built around for the next decade. 70 mm and smaller fittings look neater on a ceiling but restrict your future options.
Note: If you are replacing halogen downlights, the existing holes are almost certainly 90 mm — the old MR16 standard. A 90 mm LED drops straight in. That is the single easiest lighting upgrade in an older Australian house, and it typically cuts that circuit's consumption by around 85%.
Gimbal or fixed? A gimbal downlight tilts, so you can aim it at art, a splashback or a wardrobe. Use fixed downlights for general lighting and gimbals where you want to point at something specific. A ceiling of gimbals all aimed slightly differently looks unresolved.
IC ratings, IP ratings and insulation
Two ratings matter for a recessed fitting and people routinely confuse them.
IC rating is about insulation contact — whether ceiling insulation may touch or cover the fitting. This is a fire-safety matter, and it is why older halogen downlights required insulation to be cut away around every fitting, leaving a hole in the thermal envelope at every light.
- IC-4 — insulation may be laid over the fitting
- IC-F — insulation may abut and cover the fitting
- No IC rating — insulation must be cleared away, with a specified gap
Most of the range we stock is IC-4 or IC-F rated, which means the ceiling insulation stays continuous. That is worth real money in heating and cooling.
IP rating is about water and dust. IP20 is indoor-only; IP44 handles splashing and is what you want in a bathroom, above a shower, or under external eaves.
Watch out: On an IP44 downlight rated for insulation coverage, the driver often still has to sit above any insulation covering the fitting. Check the specific instructions — it is a detail installers miss.
What we stock
Standard 90 mm downlights
- Martec Titan II 10W — 900–970 lm, 3000K/4000K/5000K, 100° beam, CRI >80, dimmable, IP44, 90 mm cut-out — $12.35. The default choice.
- Martec Arte 10W — up to 900 lm, IC-4, IP44, die-cast aluminium, pre-connected driver, flex and plug — $25
- Martec Class II 10W — low-glare recessed reflector, aluminium housing, IP44 front, IC-4/IC-F — $32.98
- Martec Prime 10W — up to 1,080 lm, IP44, IC-F, slimline — $21.50. The brightest of the 10W fittings.
- Martec Blitz II 13W — low-profile with flush diffuser, dims to 10%, 50,000+ hour life — $10.45. Also available as a quad-colour version adding 6000K.
- Martec Niko 9W — $5.99. The budget option for garages, sheds and utility spaces.
Adjustable gimbals
- Martec Arte Gimbal 10W — tilting head, dimmable, die-cast aluminium — $32
- Martec Rex Gimbal 9W in Matt White — $15.99 · in Matt Black — $34.99. 700–780 lm, 60° beam, IP20, 5-year replacement warranty.
Specials
- Martec Zone 9W with sensor — built-in 360° detection to 4 m with a 1-minute duration, 780–850 lm, IP44, IC-4/IC-F — $29. For a pantry, robe, garage or hallway.
- Martec Arte Mini 8W — smaller aperture, low glare, IC-4/IC-F — $27
Dimming
Most of these are dimmable but need a compatible trailing-edge dimmer — a leading-edge dimmer designed for halogen will buzz, flicker or refuse to dim low. We stock the Martec rotary trailing-edge dimmer at $37 and the push-button trailing-edge dimmer at $49. Browse dimmers & controls.
Five layout mistakes
- Treating downlights as the whole plan. A ceiling of evenly spaced downlights lights a room flatly and unattractively. Layer them with wall lights, a pendant over the table, and task lighting where you work.
- Putting them in a perimeter ring. Downlights close to walls light the walls and leave the middle of the room dim. Set them out across the space.
- Mixing colour temperatures. 4000K fittings in the kitchen next to 3000K in the living room reads as a fault, not a design choice. See our colour temperature guide.
- Ignoring furniture. A downlight directly over where the TV goes, or right against the wardrobe doors, is wasted. Sketch the furniture first.
- Not dimming. A kitchen at 500 lm/m² is correct for cooking and hostile at 10pm. A $37 dimmer fixes it permanently.
In Australia, hard-wired ceiling fittings, heaters and fans must be installed by a licensed electrician. Nothing on this page is a substitute for the installation instructions supplied with the product or for AS/NZS 3000.
Frequently asked questions
How many downlights do I need for a 20 m² living room?
Around 6,000 lumens total, which is six to seven 900 lm downlights, or five to six at 1,080 lm. Space them 1,100–1,300 mm apart on a 2.4 m ceiling and keep them 600–800 mm off the walls.
How far apart should downlights be?
Roughly ceiling height divided by two, so 1,100–1,300 mm on a standard 2,400 mm ceiling and 1,200–1,400 mm on a 2,700 mm ceiling. Keep them about half that distance from the walls.
What size downlight cut-out is standard in Australia?
90 mm. It is what the old MR16 halogen fittings used, so it is what most existing ceilings are already cut for, and it is the size to specify for a new build unless you have a specific reason to go smaller.
How many lumens per square metre does a kitchen need?
400–500 lm/m² for general lighting, plus dedicated task lighting on the benchtops — typically under-cabinet strip — because ceiling downlights behind you cast your own shadow onto the work surface.
Can I put insulation over LED downlights?
Only if the fitting carries an IC rating. IC-4 allows insulation to be laid over the fitting and IC-F allows it to abut and cover it. An unrated fitting requires the insulation to be cleared away, which leaves a gap in your thermal envelope at every light.
Do I need IP44 downlights in a bathroom?
Yes for anything in or near the shower or bath zones — IP44 handles splashing from any direction. Outside those zones an IP20 fitting can be acceptable, but IP44 costs very little extra and removes the question.
Why do my LED downlights flicker when dimmed?
Almost always the wrong dimmer. LEDs need a trailing-edge (or LED-specific) dimmer; a leading-edge dimmer left over from halogen will buzz, flicker and refuse to dim smoothly at the low end.
Keep reading
Browse all downlights, oyster & ceiling lights and dimmers & controls.