Our lighting level calculators
This fact sheet provides some methods widely used by professional lighting designers on designing successful lighting, and the two calculators to put them in practice.
1- Average intensity produced by a diffuse lighting luminaire
What is the average light intensity produced in a rectangular room by a luminaire with diffuse lighting?
The first of our two calculators below allows you to estimate the average intensity (in lux) produced by a luminaire located in a rectangular room. We can specify several features of this luminaire: depending on the type of reflector or lampshade, but also depending on the type of bulb (halogen, LED or compact fluorescent) that is fitted.
A few guidelines to use the calculator:
- Choose the type of bulb with which the lamp is equipped, and enter its electrical power;
- Specify the type of reflector or lampshade with lamp: opaque or translucent, light or dark;
- Enter the dimensions (length, width, height) of the room in meters;
- Press CALCULATE. The calculator then indicates the intensity (in lux) of the illumination of the room;
- If several lamps illuminate the room, the intensities should be added: calculate the intensity produced by each lamp, and then add them;
- This calculation is fairly independent of the position of the luminaire (floor, ceiling, against a wall) and also the type of luminaire (wall, suspension, etc.). If the illumination of the room is not homogeneous, this calculator will evaluate the average intensity. A suspension placed in the middle of the room would produce a relatively homogeneous illumination (unless it has a shade that keeps part of the room in the dark).
2- Intensity produced by a luminaire with directional lighting
What is the luminous intensity produced by a luminaire which flux is directed on a given surface? The second of our calculators below allows you to predict the intensity expressed in lux produced by several types of lamps: with or without reflector, with or without shade, and with different types of bulb (halogen, LED or fluo-compact). Some guidelines to use this calculator:
- Choose the type of bulb with which the lamp is equipped, and enter its electrical power;
- Specify the type of reflector or lampshade. Office lamps equipped with a G9 bulb are often equipped with a reflector. Conventional lamps with a shade which is white inside can be considered as having a clear shade.
- Enter the size in centimeters of the illuminated area. If this surface is round, specify only its diameter.
- Press CALCULATE. The calculator then indicates the luminous intensity in lux which illuminates the surface
3- Some elements of interpretation
To interpret these results, the following information can be useful:
- To provide comfortable working conditions, a desk surface should be illuminated with 400 to 800 lux;
- To work in front of a computer, 50 to 100 lux provide soft and comfortable lighting;
- A dimly lit floor receives 25 to 50 lux;
- A 1 lux lighting is really dark;
- The lux scale is logarithmic: the eye adapts to darker environments. In full sun at noon, the lighting is around 100,000 lux. But our eye can perceive details of our environment with a lighting as low as 0.25 lux, for instance with moonlight. A home does not need to be lit like in full daylight to be comfortable!
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You can find further guidance in the following page:
- Our advices to dimension your lighting and choose your fixtures: the principles of lighting design.
- Which types of bulbs you should choose, from all the technologies now on the market - fluo-compact, LEDs etc: what you need to know about bulb technologies.
- How you should choose the LED you need, depending on your room and your expectations in terms of lighting (there is more to it than what you can read on most bulb packages): our guide to choosing LED bulbs.
- Explanation of what the various lighting units mean, and how to use them: how to speak the jargon, with lux, lumen and candela!.
- Use our calculators to size your lighting according to its purpose: our lighting calculators.
- Find your way in the jungle of the various European bulb types: our simple guide to the various bulb models.
- Read our advice on why you could consider connected lighting, and how you can jump on the train without the headaches: starting with connected lighting.
You can also find below our advice to choose and install the various types of lighting you can find in our catalogue:
- suspensions, chandeliers and pendants
- Table and desk lamps
- Wall lights
- Lighting beacons for circulation areas (indoor or outdoor)
