Kelvin, Lumens & Lux
Kelvin, Lumens and Lux – technical terms you come across when buying lamps.

If you intensively think about the topic of interior lighting you can get confused very quickly. If you deal intensively with the subject of lighting in the living room, you can also swirl your head. What does Kelvin, Lumen or Lux mean? Which technical terms should you know and which ones are more specialized knowledge for lighting planners? We give you a quick overview.


Lighting color, measured in Kelvin

The light generated by lamps has a color of its own, the so-called light color or color temperature. The color temperature is being measured in Kelvin (K). Color temperatures (“light colors”) below 2800 K are considered to be extra warm white, from 2800 to 3300 K as warm white, from 3300 K to 5300 K as neutral white and over 5300 K as daylight white. So you can remember: The higher the color temperature in Kelvin (K), the more white the light.

Kelvin-scale
Kelvin-Scale

Light is influencing our mood and our biorhythms ever since. If the clocks are getting switched to summer or winter time we notice that quite a bit. This influence on our body is, as we know today, extremely critical. A topic that “Human Centric Lighting” or “biologically effective light” deals with.

The natural phases of sunlight are “preprogrammed” like a code in our biorhythm.

They are firmly anchored in us and thus we’re also in a light mood that finds the light spectrum of the rising sun very pleasant (about 2800 – 3200 K). After that, around noon and during the early afternoon, we can help our bodies to stay productive by using a light color in the area of approximately 3300 – 6000 K (depending on the lighting purpose). Late in the afternoon, after work and in the evening, our biorhythm defines a light color of approx. 2700 – 3200 K as a feel-good light. Candlelight has a light color of about 1500 K and gives the room a warm, extra romantic atmosphere.


So for the purchase of lamps, you should choose the light sources that support and reproduce these light moods manifested in us. In areas of the house where work is being done, more light is needed. Thus a light with higher Kelvin values is advised. For more details read our furnishing tips for office lighting.

Brightness, measured in Lumens

Another important factor besides the light color is the brightness. At the time of the light bulb, each of us knew how “bright” 60 watts were. The “Watt” unit reflects the consumption of a luminaire / lamp. On the EU energy efficiency label the energy consumption of the lamp is reflected per kilowatts per hour (kWh) and shows the user how much energy the respective light source consumes. The EU’s ban on inefficient lighting has changed a lot for the consumer.

Conversion of watts into lumens

The physically correct value for the brightness is “Lumen”. Lumen (lm) is the unit of luminous flux. The luminous flux is the total amount of light that a lamp emits. This conversion from “Watts” to “Lumen” takes some time getting used to. A quick rule of thumb can help to quickly understand how “bright” the light is: 60 W incandescent lamps correspond to approx. 800 lm. The table shows more lumen values. But beware: LED light is very efficient now. Which means other values apply! Currently the many manufacturers have LED bulbs with up to 100 lm per watt in their portfolio.

If you want to replace the brightness of a 60 W bulb you would have to look for a LED bulb with approx. 8 watts (corresponds to approx. 800 lm).
Christine HillerLighting expert at Houzz & HQ Designs
Comparison chart brightness

With these two terms: Kelvin for light color and Lumens for brightness your lighting purchase should go way smoother. In case of professional lighting planning, other terms also play a key role. The calculation of these light variables can be fairly complicated but it’s good to know the terms at least.

Light intensity, measured in Lux

The intensity with which a light source impinges on a surface (depending on the distance) is called the Light intensity (E). Lux is the measure of the brightness at a particular location. Since the calculation depends on several individual factors, this value is not to be found on luminaire packages and if so then usually only as a guideline (calculation on one meter distance).

Even though this term might not be understandable for the average consumer, with this value the interior designers can determine whether the light is sufficient e. g. to illuminate a desk the right way. For laboratories and public places precise guideline values are required in the interests of occupational health and safety. These guideline values are used to determine whether a workplace, paths or public spaces are perfectly illuminated. This ensures that employees don’t damage their eyes in the long term because the workplace is insufficiently illuminated.


These guideline values are defined in DIN 12464 part 1 for workplaces and interiors of different sectors. For the illustration above we have selected some values for you to refer to normal residential situations.

Important: these are values defined by the requirements of visual tasks, activities and the type of space. This is supposed to be a guide of how high the light intensity should be. However it is always important which requirements each person has personally, thus there’s no general recommendation for living areas.


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