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What’s the difference between lumens, kelvins and watts?

What’s the difference between lumens, kelvins and watts?

We know that many of our customers get confused when trying to choose a new lamp (also referred to as a bulb) for their lighting, and if you’ve gone to a supermarket, with all of the options from lumens, kelvins and watts, how do you decide? Let’s help.


The lumens of a lamp is the total light output – basically, how bright the lamp is. The more lumens, the brighter the lamp will be. It’s important to note that lumens and watts are different measurements, with lumens being used to describe the brightness, not the amount of energy a lamp consumes. As lamps are becoming more energy efficient (especially LED), you’ll commonly see the same number of lumens being achieved with less wattages than in previous years.

That’s also why, if you’re switching from incandescent lamps (those which do traditionally use wattages as a measurement), then this guide might help you decide which lumens to choose:

  • A 100 watt lamp would give you roughly 1600 lumens
  • 75W is roughly 1100 lumens
  • 60W is roughly 800 lumens


This is the measurement used to describe the colour temperature of a lamp (think warm versus cool). Why is it measured in Kelvin though?

When you heat a piece of metal, the colour of light it emits will change – you might have seen videos of this online. It begins as a red, but will gradually change colour from that to orange, yellow, white then a blue white – reflecting the temperature, which is a measured in degrees Kelvin.

We associate warm colours with yellows and reds, while cooler colours are associated with blues and greens. Now, just to confuse matters, the lower down the scale you are (for example, 2000K to 3000K) the warmer the temperature of the lamp will be. Just remember why it’s measured in Kelvin and it’ll make sense.

Most indoor lighting will have a colour scale of 2700-3600K, but this will change if in office or work locations depending on the field of work. For example, cooler light is preferred for visual tasks (videos on YouTube perhaps), because it produces a higher contrast than to warm lighting.


We’ve already touched on the fact that wattage is the measure of energy consumed – which is why traditionally, before energy efficient lighting and LEDs, the higher than wattage, the brighter the lamp. As technologies have improved lighting though, there’s no hard or fast rule anymore. To be honest, one brand might be more efficient compared to another when it comes to watts vs lumens, so it’s really a case of trying to look at both measurements when decided on your new lamps.

If you’re not sure and Electrical Estimates are working with you on your new lighting, just ask us, we’re more than happy to help and advice. We’d also highly recommend switching to LED lighting if you haven’t already, they generally use 90% less energy than a traditional incandescent lamp.