April 23rd, 2020 by Sarah Miles

Unless you have a keen interest in lighting design, chances are you’re probably not aware of the term ‘Kelvin’ when looking at light bulbs. However, you may have noticed a number followed by a K on the light bulb packaging when you’re browsing the shops.

You may not have heard of it, or – if you have – you may not really know what it means, but the Kelvin rating is really useful to understand when choosing home lighting. It allows you to choose the right light bulb for its purpose, whether at home or in a commercial environment. As form follows function, this is really just as important as the aesthetic appearance of the lighting itself.

The Kelvin rating is used to measure the colour temperature of a particular light bulb. To give it its technical definition “the SI base unit of thermodynamic temperature, equal in magnitude to the degree Celsius.”. Don’t worry, you don’t have to understand the science; an easier way to understand it is a scale of how white the light bulb is: the higher the Kelvin number, the whiter the light emitted.

This is what’s more commonly known as colour temperature and Kelvin is the unit of absolute colour temperature. In home interior design, we often choose our lighting to go with the look and feel of the room but what we should also take into consideration is the purpose of that space to ensure that the level of light is appropriate. This is where the Kelvin rating will help you.

Some rooms may require low, ambient lighting – such as a living room. Some, where tasks need to be completed, require good light levels – such as a kitchen or home office. A commercial environment may require whiter light still.

Here’s a guide to Kelvin ratings and where you might use each one:

Less than 2700K

Emits a low, dim glow of light, similar to that of a candle (a candle flame is typically around 1850K). This light will be a warm light. This level is generally a little too dim, even for living rooms.

2700-3500K: Warm White

This offers a warm white glow and is commonly used for relaxed areas such as living rooms and bedrooms.

3500-4500K: Cool White

White light has a neutral colour temperature at around 3500K so we’re beginning to see more white in this range. This is appropriate for ‘task lighting’ ie, lighting required to enable you to complete a task such as cooking or working. Therefore this K rating is most suitable for kitchens and home offices.

4500-6500K: Bright White

This emits a bright, blue-white light, similar to that of full daylight. This K rating is rarely appropriate for domestic environments and is more commonly used in commercial spaces such as offices, factories and hospitals.

Next time you buy light bulbs, as well as looking at the wattage, pay close attention to the Kelvin rating and this will help you choose the most appropriate bulb for the purpose of the space.