The calculator suggests a colour temperature in Kelvin based on the room, the time when you use the light and what you do there. For living rooms and bedrooms it usually arrives at 2700 K, for the kitchen and bathroom at 3000 K, and for a workspace you use during the day at 4000 K. If you already have lights in the room, it advises you to match their colour temperature.
What does this calculator do?
It turns three questions into a colour temperature: in which room is the light on, when is it on, and what do you do by that light. The result is a colour temperature in Kelvin, with the range within which you can choose, and advice on the technology: a fixed colour temperature, dim-to-warm or tunable white.
A lower Kelvin value means warmer, more yellow light; a higher one means cooler, whiter light. What the values mean and what they look like is explained in choosing a colour temperature.
How does the tool arrive at its advice?
- Starting value per room. Each room has a starting value and a range, according to the table below.
- Time and purpose. If the light is mainly on in the evening to relax, the advice shifts to the warm end of the range; in the living room and dining room it stays at 2700 K, with 2200 K or dim-to-warm for ambient light. If it is on during the day alongside plenty of daylight, or you want to see detail and work, it shifts to the fresher end, but never above 4000 K.
- Existing lights. If you enter the colour temperature of the lights you already see in the same room, the tool follows that value as long as it falls within the range. Lights in one field of view should preferably not differ by more than 300 K.
- Technology. If you use a room both during the day and in the evening, the tool suggests dim-to-warm for ambient light and tunable white for a kitchen, bathroom or workspace.
| Room | Starting value | Range |
|---|---|---|
| Living room | 2700 K | 2200–3000 K |
| Dining room | 2700 K | 2200–3000 K |
| Bedroom | 2700 K | 2200–2700 K |
| Kitchen | 3000 K | 2700–4000 K |
| Bathroom | 3000 K | 2700–4000 K |
| Home office | 4000 K | 3000–4000 K |
| Hall and stairs | 2700 K | 2700–3000 K |
| Outdoors | 2700 K | 2200–3000 K |
What is the advice based on?
Licht.de, the knowledge centre of the German lighting industry, recommends warm white of 2700 to 3300 K for the living room. According to the usual classification, warm white is below 3300 K and neutral white between 3300 and 5300 K. The tool therefore stays in the warm range in living spaces and only moves to neutral white for the kitchen, bathroom and workspace.
The evening rule comes from sleep science. Recommendations published in PLOS Biology in 2022 call for little light that stimulates the body clock in the three hours before bedtime, and according to the same publication warm white LEDs of 2700 to 3000 K meet that limit more easily. Quantity matters just as much: dim the light in the evening as well.
No colour temperature is more pleasant in itself. A review of research by Steve Fotios found that people mainly find too little light unpleasant, and have no preference for a particular colour temperature. The tool’s advice is therefore about light that suits the room and the moment, not about right or wrong.
Frequently asked questions
Why does the tool never suggest more than 4000 K?
Because cooler light is rarely pleasant in a home. Light of 5000 to 6500 K makes sense in a garage, a studio or a hobby corner where you judge colours. If that is what you want, enter “seeing detail” as the purpose and then choose a daylight bulb yourself.
What if my existing lights have different colour temperatures?
Enter the colour temperature of the lights that give the most light or that you see most often. Replace the odd ones out at the next opportunity, or put them somewhere you do not see them next to the others.
Can I change the colour temperature of my current lights afterwards?
Not with ordinary LED bulbs. With fixtures that have tunable white, a selector switch, or with a smart bulb, you can. Dim-to-warm bulbs only change colour when you dim them.
Sources
- Light for living and well-being in the living room, licht.de (2025)
- licht.wissen 14: Ideas for Good Home Lighting, licht.de (2009)
- Recommendations for daytime, evening, and nighttime indoor light exposure to best support physiology, sleep, and wakefulness in healthy adults (Brown e.a.), PLOS Biology (2022)
- A revised Kruithof graph based on empirical data (S. Fotios), LEUKOS, Illuminating Engineering Society (2017)
