How many downlights you need for any room — based on Australian lux standards, ceiling height and room type. Includes grid spacing layout.
The calculator uses a lumen-based method to determine how many downlights are needed to reach a target lux level for your room type. It then works out a grid spacing layout based on the standard rule that the first row of lights sits half the spacing distance from the wall, with lights evenly distributed across the room.
The following targets are based on Australian and New Zealand lighting standard AS/NZS 1680 and general residential best practice:
| Room type | Recommended lux | Notes |
|---|---|---|
| Kitchen (general) | 300 lux | Supplement with under-cabinet task lighting over benchtops |
| Living / dining room | 200 lux | Use dimmable fittings for flexibility |
| Bedroom | 150 lux | Bedside lamps supplement general lighting |
| Bathroom | 300 lux | Vanity mirror lighting should be additional |
| Study / home office | 400 lux | Higher requirement for sustained task work |
| Hallway / passage | 100 lux | Safety and navigation — not task lighting |
| Laundry | 250 lux | Task-oriented space, good general light needed |
Lux is a measure of light falling on a surface. One lux equals one lumen per square metre. To hit a target lux level across a room, the total lumens needed equals the target lux multiplied by the room area, divided by a utilisation factor.
The utilisation factor (0.6) accounts for light that hits walls and ceilings rather than the floor or work surface. A maintenance factor (0.8) accounts for lumen depreciation as LEDs age. These are standard residential values.
A reliable rule for even downlight spacing is:
This calculator works out the actual grid (rows × columns) that best fills your room dimensions while keeping spacing even.
The calculator gives a starting point for ambient general lighting. You may want to increase the count if the room has dark surfaces (navy walls, dark timber floors) which absorb light. You may want fewer if you plan to supplement with floor lamps, pendant lights or under-cabinet lighting.
Always confirm the final layout with your electrician before cutting holes — they'll account for ceiling joists, insulation clearance and circuit load.