Colour temperature is a technical characteristic of light sources such as LED lighting.
Colour temperature is expressed as a four-digit number in the unit kelvin, a measure of absolute temperature, using the symbol K. For example, 2700K, 3000K, 4000K, or 6500K. Terms like warm white, cool white, or daylight are also used to describe these colours.
The scale corresponds to the colour of light emitted by an 'ideal black body' at these actual temperatures. We can mostly skip the physics, but here are two examples to try and explain the concept:
- The sun has an actual temperature of about 5800K (5527˚C). Its emitted radiation peaks in a part of the visual spectrum that we perceive as 'daylight'.
- Molten lava has an actual temperature of about 1300K (1027˚C). The light emitted at this temperature is an intense orange or red 'warm white' glow.
Some familiar examples to explain the technical underpinnings of 'colour temperature'.
Colour Temperature Guide - 2000K vs 3000K vs 4000K vs 5000K vs 6000K Light
The image below provides a quick reference or guide to some common colour temperatures.
2000K vs 3000K vs 4000K vs 5000K vs 6000K colour temperature.
The Colour Temperature Scale
For most LED lights, colour temperature ranges from 2000K candlelight to 6500K cool white. In between, there are a wide range of colour codes and an even more comprehensive range of words used to describe them.
Note: the technical term is Correlated Colour Temperature (CCT). For this reason, you will often see it labelled as CCT in lighting specifications.
Colour temperature chart and examples.
| Colour Temperature | Examples |
|---|---|
| 1700K | Match flame, low-pressure sodium lamps (orange streetlights) |
| 1850K | A candle flame, sunset & sunrise |
| 2400K | Standard incandescent or filament lamps |
| 2700K | Soft white compact fluorescent and LED lamps |
| 3000K | Warm white compact fluorescent and LED globes |
| 4000K | Neutral white or cool white fluorescent tubes |
| 5000K | Horizon daylight |
| 5500 – 6000K | Vertical daylight, electronic flash |
| 6500K | Cool daylight fluorescent tubes, overcast |
| Note: terminology and actual correlated colour temperature vary extensively. Examples modified from Wikipedia. | |
Colour Temperature Words ≠ Actual Temperature Reality
Somewhat confusingly, the way we describe colour temperature is the opposite of actual temperature.
The higher the colour temperature on the Kelvin Scale, the 'cooler' the colour. The lower the colour temperature, the 'warmer' the colour. This is despite the fact that the source temperature (remember the 'black body radiation' from earlier) is most definitely 'warmer' at 6000K than it is at 3000K.
It's no wonder why so many people find themselves purchasing the opposite colour temperature light to what they had in mind!
Use The Colour Temperature Numbers
To avoid all this confusion, you should focus on the numbers, not the words. Here's why:
One brand's 5000K could be described as 'daylight', whereas another could refer to the same colour temperature as 'cool white'.
There is even some variation within one brand. For example, we have noticed that Philips describes 4000K bulbs as 'cool white'. Yet, the exact same colour temperature in fixtures is routinely described as 'neutral white'.
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Therefore, if you’re trying to match or replace a specific colour temperature, it's best to ignore the descriptive words and look at the kelvin number. The same rule applies if you’re comparing two different products.
The International Colour Temperature Code
Colour temperature is also specified with another code like 830, 840 or 965. These codes combine two lighting specifications into one: colour rendition and colour temperature.
The first number refers to colour rendition:
- 8 = colour rendering index Ra 80 – 89
- 9 = colour rendering index Ra 90 – 100
The second and third numbers refer to colour temperature, for example:
- 27 = 2700K light
- 30 = 3000K light
- 40 = 4000K light
- 50 = 5000K light
- 65 = 6500K light
An example colour temperature code on an LED Fluro Tube.
The Difference Between 'Warm White' & 'Cool White' Lights
Generally, 'warm white' is atmospheric and 'cool white' is functional.
The choice of colour temperature can be used to foster certain moods. This is similar to how some colours have cultural connotations (e.g. red = passion, blue = calm).
TIP: See our Philips Hue Smart Lighting range for lights that have full colour spectrum control.
Lower colour temperatures are described as 'warm' because they remind us of fire or candlelight. Warm white or soft white colour temperatures create a cosy atmosphere in bedrooms, cafes and restaurants.
Vintage-style filament LED bulbs are perfect for cafe, restaurant or lounge room lighting. They have a colour temperature of 2000K to 2700K.
Higher colour temperatures tend towards blue and are considered 'cool'. Actual daylight is about 5500K to 6000K. So if you want to recreate the feeling of natural light, go for a higher colour temperature.
Higher colour temperatures are also generally perceived as brighter. They’re great for work areas like kitchens and offices. Note: if you’re looking for more brightness - the specification to check is lumens, not colour temperature.
A downside to high colour temperatures is that they can appear stark, harsh or sterile. For example, hospitals and 7-Eleven stores tend to use high colour temperatures.
A 4000K LED panel to replace fluorescent fittings in offices.
Colour Temperature Consistency is Key
Colour temperature discrepancies are more apparent when two lights of different colours are right next to each other. Mismatched lighting can seem incongruous. So whatever you choose, try to keep the colour temperature consistent within a space. For example, all the LED downlights used in one room should match.
Consistency can be problematic in open plan living, where the kitchen and living areas are in the same room. A cooler colour like 4000K might work in the kitchen but seem too stark for the lounge. Likewise, a warm colour like 2700K might be great for the living area but not practical enough for working in the kitchen. In this case, meeting in the middle at 3000K is a good compromise and keeps the light consistent throughout the space.
That’s probably why 3000K is the highest selling colour temperature for our LED downlights. Its versatility makes it a popular choice. That being said, don’t be afraid to use different colour temperatures in separate rooms if you need to.
You can also have one colour temperature for ceiling lights and another for floor and table lamps. This allows you to switch between the two modes of lighting for different occasions.
When in Doubt, Stick With Colour Temperatures That You're Familiar With
If you're upgrading an old light to LED, ask yourself, what colour temperature are you replacing? Do you like what is there? If yes, then there’s no harm in simply trying to match it.
TIP: Check the small print on the light bulbs or tubes you already own to see their colour temperature.
Colour temperature is usually written on the back of the bulb.
Most LED retrofits already have colour temperature options that match old globes. Don't worry if you can’t find an exact match - near enough should be good enough.
Can’t Decide? Try a 'Tri Colour' Light Fitting
Some LED lights can even change their colour temperature. Two examples are:
- Tri colour light fittings. These have a switch on the back of them so you can change the colour temperature post-purchase. These are sometimes specified as '3CCT'.
- Smart or wifi light bulbs like Philips Hue. These light bulbs are controlled via an App on your phone. They are sometimes described as 'tunable white' or 'RGB' for full-colour control.
