Lighting Lumen Calculator
Enter the room, its size and the ceiling height to get the total lumens needed, the LED wattage, and for downlights the number and spacing — plus the right colour temperature.
Brightness is measured in lumens, not watts — a 12 W LED can be brighter than a 60 W bulb. Pick the room, enter its size and ceiling height, and the page returns the total lumens, the LED wattage, the downlight count and spacing, plus a colour temperature that suits the room.
Room and fixtures
Lengths in metres. Results update as you type.
Total lumens needed
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LED wattage
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Downlights
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Spacing
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Colour temperature
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Recommended illuminance
| Room | Illuminance | Colour temperature |
|---|---|---|
| Living room | 150 lux | 3000–4000 K |
| Bedroom | 100 lux | 2700–3000 K |
| Kitchen | 300 lux | 4000 K |
| Study | 300 lux | 4000 K |
| Dining room | 200 lux | 3000 K |
| Bathroom | 150 lux | 4000 K |
Before you buy
- Compare lumens, not watts. Wattage only tells you how much power the lamp draws.
- A single ceiling light lights the middle of the room brightly and the corners dimly. Rooms over about 20 square metres usually need a second layer, such as a floor lamp or downlights.
- Keep one colour temperature per room. Mixing 3000 K and 6000 K in the same sightline looks dirty rather than bright.
- For downlights, the spacing should be roughly equal to the distance from the wall to the first row, so light lands on the walls, not only the floor.
- Choose CRI 80 or above for general rooms, and CRI 90 or above over a dining table or a mirror.
- Dimmers need dimmable lamps and a compatible driver; otherwise the light will flicker at low output.
Five common mistakes
- Buying by wattage and ending up with a room that is bright in the middle and dark at the edges.
- Ignoring ceiling height: the same lamp in a 2.6 m and a 3.2 m room gives very different light on the floor.
- Using 6000 K cool white in a bedroom — it reads as a hospital corridor.
- Pointing downlights straight at a sofa or a mirror, which puts glare in the sightline.
- Forgetting the kitchen worktop and the bathroom mirror, where task light matters more than ceiling light.
Reference values for ordinary residential rooms. Colour, wall finish and furniture change the result — confirm with a lighting designer or electrician before installation.