Colour Temperature Explained

What is colour temperature in lighting?

Colour temperature, also written as color temperature, describes the apparent colour of light, from warm white to cool white. The Kelvin scale for lighting is listed on a bulb as correlated colour temperature (CCT), measured in kelvin (K). Shoppers also search for “light colour temperature” or “colour temp” when comparing this value. Lower Kelvin values appear warmer and more yellow; higher values appear cooler and bluer. A bulb’s colour temperature, also called bulb colour temperature, is not its physical operating temperature or heat output. It also does not measure brightness, which is compared in lumens, or colour rendering, which is described separately by the colour rendering index (CRI).

The phrase “light temperature” is often used to mean this colour appearance; a search for “lamp temperature” can mean the same thing. Neither phrase describes how hot a lamp gets. When choosing a replacement, compare the stated Kelvin value rather than relying only on “warm white” or “daylight”; product naming varies. For a cool white versus warm white choice, compare the figures and the look you want.

Colour temperature chart: warm white, cool white and daylight

Use these common reference points as a guide. They describe light appearance, not a fixed naming rule for every manufacturer.

• 2700 K: usually labelled warm white, with a warm yellowish appearance.
• 3000 K: often labelled soft white or warm white, generally a little less yellow than 2700 K.
• 3500–4000 K: commonly described as neutral white. A 4000 K colour temperature may be labelled neutral white or cool white, depending on the product range.
• 4100–5000 K: often described as cool white.
• 5000–6500 K: cooler daylight or cool-white appearance. The CIE D65 daylight reference has a correlated colour temperature of approximately 6500 K.

Warm white bulbs: 2700 K and 3000 K

People comparing warm white colour often start with 2700 K and 3000 K. Both are common warm-white choices, while 2700 K generally looks more yellow and 3000 K a little cleaner or whiter. This difference is a useful guide, but the exact appearance also depends on the lamp and its surroundings. Check the product’s stated Kelvin value when matching bulbs in the same room.

4000 K colour temperature: neutral or cool white?

A 4000 K bulb sits between warmer white and higher daylight values. Some product ranges call it neutral white; others use cool white. If the existing lamps look right and you want a consistent result, use their Kelvin rating as the comparison point. For a new installation, choose by the appearance you prefer and check the product description rather than assuming every “cool white” bulb has the same colour temperature.

Daylight colour temperature: 5000 K to 6500 K

Higher Kelvin values usually look cooler and bluer than warm-white light. Products described as daylight can have different stated values, so check the specification: 6500 K is an approximate reference for CIE standard illuminant D65, but a lamp marketed as daylight is not necessarily rated at exactly 6500 K. Two light sources with the same nominal CCT can still look different because CCT describes only one part of their colour appearance.

How to choose a light colour temperature

1. Start with the room and task. Warm white is a common preference for a softer, familiar appearance. Neutral or cool white may suit areas where a clearer, less yellow look is wanted. Personal preference and the finish of the room matter.
2. Keep nearby lamps consistent. If several fittings illuminate the same area, compare their Kelvin ratings. Mixing warm white and cool white can make the difference in appearance obvious.
3. Compare the right specifications. Use lumens to compare brightness and CRI to compare colour rendering. Check the bulb fitting, dimming compatibility and other product details separately; Kelvin does not tell you whether a bulb will fit or work with a dimmer.

Walls, furniture, daylight and lamp shades all affect how a light colour looks in a room. When appearance needs to match closely, compare the actual products in the intended setting where practical.

For offices, shops and other commercial spaces, record the selected CCT and keep it consistent across fittings where a uniform appearance matters. Follow the lighting design and task requirements for the installation.

Colour temperature in photography and videography

In photography and video, colour temperature helps describe the appearance of a light source and can guide camera white balance. When a scene uses sources with different colour temperatures, parts of the image can take on different colour casts. CCT is a useful comparison, but it does not describe the source’s full spectrum; two sources with the same Kelvin rating may render colours differently.

Colour temperature and CRI are different

Colour temperature describes whether light appears warm or cool. CRI describes how a source renders object colours compared with a reference. These are separate properties: a Kelvin value is not a CRI score. If colour accuracy matters for the application, check the product specification for both measures rather than using colour temperature as a substitute for CRI.

Common colour temperature questions

Is 4000 K warm white or cool white?

It is often sold as neutral white, although some ranges call it cool white. Compare the Kelvin rating and product description for the exact lamp.

Is 6500 K the colour temperature of daylight?

6500 K is an approximate CCT for the CIE D65 daylight reference. Products described as daylight may use different Kelvin values, so check the listing.

Does a bulb’s Kelvin rating tell me how hot it gets?

No. Kelvin on a lighting specification describes colour appearance. It is not the bulb’s operating temperature or heat output.

Once you have chosen a light colour, browse our LED bulbs and lamps or LED ceiling lights. Check each product for its fitting, brightness, Kelvin rating and dimming details.