Lighting: calculate the useful power and the number of bulbs

Method of calculating the required lighting power and the number of bulbs / light points. Examples in energy saving lighting

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- Choosing lighting in the kitchen and bathroom
- Range of Megaman bulbs in natural daylight (sun color)

Many people wonder about the recommended light output and the number of bulbs needed. The vagueness and commercial blahs being legion, here is a summary article of the sizing of the lighting of a room.

To begin with, you should know that the lighting power in Lux is a rather subjective quantity: some people will be content without problem with 80 lux in their living room while others will want 300!

Also the type of light (spectrum of lighting) plays a lot: a bulb in natural sunlight will give an impression of much more light while the lumens of the source are the same.

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Recommended lighting powers (high scale)

  • Stairs, basements, attics: 30 lux
  • Garages, hallway, utility room: lux 60
  • Kitchen, game room, lounge, dining room, local housework, waiting room: lux 250
  • Room, kitchen work and leisure, secretarial and lab: 500 lux
  • Entrance hall, shower room, bathroom, children's room, pantry: 720 lux
  • Reading, writing, crafts, homework, crafts, drawings, makeup: 750 lux
  • Architecture, accurate work, precise control, differentiate colors 7000 lux

Regulatory lighting powers according to wikipedia

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Examples of other common lighting powers (for comparison)

  • Sensitivity of a low level camera: 0,001 lux
  • Moonlit Night: 0,5 lux
  • Well-lit night street: 20 - 70 lux
  • Local life: 100 - 200 lux
  • Well-lit apartment: 200 - 400 lux
  • Work room: 200 - 3 lux
  • night stadium: 1 500 lux
  • Outside overcast sky 25 000 lux
  • Outdoors in direct sunlight: 50 000 100 000 to lux

The disparity of these values ​​confirms my first remark on the subjectivity of lighting.

Calculation method of lighting design

It's pretty simple.

- 1 Lux = 1 Lumens / m²
- With the surface of the room to be lit and the desired number of lux, you obtain a number of Lumens.
- By knowing the Lumens per bulb, you have the number of bulbs necessary to install and therefore of light points / wall lights / lights to install.

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