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Understanding Lumens: what you need to know

understanding lumens

When choosing the best lamps (commonly known as light bulbs) for outdoor light fittings, most people will instinctively look to the wattage as a measure of brightness. However, thanks to the widespread popularity of LED technology, wattage is now becoming less and less relevant. The new unit of measurement that should spike your attention when it comes to brightness is the lumen.


What is a lumen?

The lumen is defined as “a unit of luminous flux in the International System of Units, that is equal to the amount of light given out through a solid angle by a source of one candela intensity radiating equally in all directions.

Or, put simply, lumens are the measurement of the total amount of light produced by a light source. Lumens represent the brightness of a light, the higher the lumens the brighter the light and the lower the lumens the dimmer the light.

Lumens = light output


Comparing watts and lumens

Watts are used to measure the amount of energy used by a lamp to produce light. However, despite still being an important measurement of energy efficiency, the move towards the use of more energy efficient lamps means that wattage is no longer the most accurate way to determine brightness. If you want more of an understanding of how bright your light will be then it’s better to choose products based on their luminous flux. After all, the purpose of a lamp is to illuminate an area, so it makes more sense to compare lamps based on light output rather than energy consumption.

Most lamps are now supplied with both a wattage and lumen figure, which makes it easy for you to compare old lamps with new lamps to find the equivalent product when it’s time to replace them. For example, our E27 Filament Lamps are clearly labelled with both wattage and lumens; The 8W version has 1000lm and the 12W watt alternative has 1500lm.

guide to lumens

Working out the most efficient solution

With low energy LED lamps, a higher light output can be achieved whilst also consuming less energy. Our 3.5W LED GU10 lamp will give a similar light output to a 50W Halogen lamp despite its higher wattage, which means you’re getting the same performance but saving a huge amount of energy!

Finding the most energy efficient solution is now rightly a top priority when it comes to choosing lamps. You can compare the efficiency of two lamps by working out the lumen per watt measurement for each. All you need to do is divide the number of total light output in lumens by the power usage in watts; the higher this figure the better the efficiency and lower the running costs.



Watts: 10

Lumens: 1200

Lumen per watt: 120lm/W


What should you be looking for?

Each outdoor space has its own lighting requirements and therefore varying levels of lumens will be required to achieve the overall desired effect. The amount of brightness needed will depend on the light fitting and its purpose within a setting. For example, a spotlight being used to highlight particularly important features in the landscape may require a lamp with a higher light output, whereas a classic lantern doesn’t require the same level of intensity as the light is spread in all directions. In fact, in some cases choosing a very high luminous flux can cause issues, particularly for applications such as street lamps where brightness can affect the visibility of drivers and pedestrians.

When you browse our outdoor lighting range you’ll notice that we have included the wattage and luminous flux of the different lamp options for that particular product, to help you in your decision. You can also view all of our LED lamp options and the relevant specifications.




If you would like more guidance on lumens and how to choose the best lamps for your application get in touch with our team today on 0330 700 3000 or email us at [email protected]

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