Lighting
Lighting calculator
A bedroom needs an average of 75 lux and a corridor only 50, while a living room, kitchen or bathroom needs 100. So a 4 × 4.5 m bedroom with a 2.6 m ceiling takes 5 downlights of 800 lumens.
Enter the room size and ceiling height, pick the type of room, and see how many lux it needs, how many lumens that takes and how many downlights, with a light map of the floor. It runs the same module as the RAYA app.
Lighting calculator
5 downlights
Target 75 lux · needs 3,360 lumens
- Average with that many
- 89 lux
- Total lumens
- 4,000 lumens
- Uniformity of direct light
- 0.51, below 0.4, so there are dark corners
Enter the room size and the lumens as numbers above 0.
The downlights are spread evenly on the ceiling. The average uses the lumen method; the map counts direct light from the lamps only, not what walls and ceiling reflect.
Targets
Each room needs a different amount of light
A target is the average on a 0.75 m table-height plane, or on the floor for a corridor. Where a room has a task area, such as a reading corner or a kitchen worktop, add local light there to reach the right-hand column.
The lumens needed are the target times the area, divided by the room's utilisation factor and a maintenance factor of 0.79 from the Thai Illuminating Engineering Association's guide.
| Room | Whole room | Task area |
|---|---|---|
| Living roomGB 50034-2013 table 5.2.1 | 100 lux | 500 luxReading corner · TIEA ch. 4 sec. 26 p. 45 |
| BedroomGB 50034-2013 table 5.2.1 | 75 lux | – |
| KitchenGB 50034-2013 table 5.2.1 | 100 lux | 500 luxFood preparation · TIEA ch. 4 sec. 24 p. 44 |
| BathroomGB 50034-2013 table 5.2.1 | 100 lux | – |
| Dining roomGB 50034-2013 table 5.2.1 | 150 lux | – |
| CorridorGB 50034-2013 table 5.2.1 | 50 lux | – |
| StudyTIEA 3.2.2–3.2.3 p. 14 | 100 lux | 500 luxWriting and reading at a desk · TIEA ch. 4 sec. 22 p. 43 |
| Shop (sales floor)TIEA ch. 4 sec. 23 p. 44 | 300 lux | 500 luxTill · TIEA ch. 4 sec. 23 p. 44 |
Common room sizes
How many downlights for a room this size?
These figures use a 2.6 m ceiling, 800-lumen downlights and each room's general target from the table above, with the same calculation as the calculator. With a higher ceiling, or lamps of a different output, put the real figures into the calculator.
| Room | Size (m) | Lumens needed | Downlights |
|---|---|---|---|
| Bedroom | 3 × 3 | 1,970 | 3 |
| Bedroom | 3 × 4 | 2,470 | 4 |
| Bedroom | 4 × 4 | 3,060 | 4 |
| Living room | 4 × 5 | 4,870 | 7 |
| Living room | 5 × 6 | 6,710 | 9 |
| Kitchen | 3 × 4 | 3,290 | 5 |
| Dining room | 3 × 4 | 4,940 | 7 |
| Bathroom | 2 × 2.5 | 1,760 | 3 |
| Corridor | 1.2 × 6 | 1,270 | 2 |
In the app
Every lamp on the real plan
In the RAYA app, the light comes from every lamp you place in the room, downlights, pendants, floor lamps and hidden strips, checked against the room's target, with a light map on the plan showing the dark corners.
See a real room in Design your own home
FAQ
Questions about lighting
- How many downlights for a 4 × 4.5 m bedroom?
- With a 2.6 m ceiling, a bedroom aims for 75 lux and needs about 3,360 lumens: five 800-lumen downlights, for an average of about 89 lux.
- What is the difference between lux and lumens?
- Lumens are the light a lamp gives out, printed on its box. Lux is the light landing on a surface: 1 lux is 1 lumen per square metre.
- I do not know my lamp's lumens. What should I enter?
- The calculator starts at 800 lumens, as bright as a 60 W incandescent bulb. If the box gives the lumens, enter that instead.
Terms
Terms on this page
More words you meet when doing up a home are in the Interior design glossary
Arrange your first room
You can start from a sample room. Stuck anywhere? Message us on LINE @raya-studio or see plan prices on the home page
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