Convert Lumens to Watts and Watts to Lumens the Right Way

Convert Lumens to Watts and Watts to Lumens the Right Way

The conversion between lumens and watts is important if you want to replace old light sources with modern LED lamps. In case of LED lamps and luminaires, the specified wattage plays only a subordinate role. More important is the actual brightness, which is given in lumen. Here you will find all necessary information to calculate the needed lumens for your preferred brightness.

Conversion between Lumens and Watts

This article explains the difference between lumens and watts and why the lumen value is an important specification for modern LED lighting. You can get a quick overview on the Lumen Watt Comparison Table. The article also offers an online calculator with two main functions:

  • Convert lumens to watts
  • Convert watts to lumens

Convert lumens to watts

Old light sources such as incandescent bulbs or halogen lamps were easy to choose. Here the wattage was the most important indicator for the brightness. If a 60W bulb fails, it could be simply replaced by a new 60W bulb. The replaced lamp was just as bright as before and there was no need to worry about the correct brightness.

For LED lamps, the power consumption is also indicated in watts. However, the wattage plays a minor role now and allows only a very rough conclusion on the actual brightness. Different components in various LED lamps lead to varying brightness with the same power consumption.

For example, a 5W LED illuminant of type A can light up much brighter than a second 5W LED lamp of type B. This is possible because lamp A could achieve a better efficiency through higher quality components and therefore emits more light. For the comparability of LED lamps the brightness is indicated in lumens.

What are lumens?

The unit lumen describes the luminous flux emitted by a lamp. This is the power emitted per second in the wave range of visible light. For LED luminaires and illuminants, this must always be stated in the product description. The lumen specification is often given in the short form lm.

The lumen value can be used to compare the brightness of different lamps, irrespective of efficiency and lighting technology used. The brightness in lumens is particularly important when using LED lamps. The Lumens to Watts Calculator helps you to compare the brightness of different light sources.

Lumens to Watts Converter

This free online calculator will help you convert lumens to watts and vice versa. So you can calculate how many lumens the new LED lamps should have based on your previous lighting. If you already have some LED lamps in the closer selection, you can convert their lumen value into the output (in watts) of previous lights.

Lumen Watt Calculator

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Calculator help

Lumens to watts conversion

Example 1: You see an offer for an LED torchiere. The light output is 1800 lumens and you want to know how bright it is compared to an old halogen torchiere.

In the calculator you have to select Lumens to Watts as conversion type, enter the value 1800 and select the item Halogen lamp as comparison type. After a click on the calculate button you will see the wattage of an equally bright halogen torchiere.

Convert watts to lumens

Example 2: You have a torchiere with two 35W bulbs and want to replace them with LED lights.

In the calculator, select Watts to Lumens as the conversion type, enter the value 35 and select the item Light bulb for comparison. After a click on the calculate button the luminous flux is displayed in lumens. The result should serve as a guideline for the brightness of the new LED lights.

Lumens to watts comparison table

This table shows a comparison of the power consumption and the respective brightness of all common light sources. The lumen values are average values of the respective lighting technology.

Comparison of power consumption (in watts) and brightness (in lumens) of different lighting technologies
PowerLight bulbHalogen lampEnergy-saving lampLED
5 W180 lm500 lm
7 W290 lm700 lm
9 W400 lm850 lm
11 W530 lm1200 lm
14 W730 lm1500 lm
25 W230 lm300 lm
40 W430 lm500 lm
60 W730 lm900 lm
75 W970 lm1200 lm
100 W1380 lm1700 lm

The brightness specifications for LED technology varies greatly depending on the quality of the light sources. Due to the active development of LED technology, a further increase in lumens per watt can be expected in the coming years.

Important notes for lumens to watts conversion

The luminous flux or brightness in lumens indicates the intensity only. The direction or beam angle of the emitted light is not taken into account. So the lumen value says nothing about how the light is diffused in the room. Old light bulbs and halogen lamps emit their light almost all around. Many LED lamps, on the other hand, have a lower beam angle.

For this reason, the lumen value of an LED lamp can often be slightly lower than with the old light source. With a luminaire above the dining table for example, the table would be illuminated just as brightly as before, only the indirect lighting of the ceiling would be darker than before.


Before you replace old light sources with modern LED lamps, you should think about the desired brightness. This avoids disappointments that the new LED lamp is much darker than the old incandescent lights.

To find LED lamps with the correct brightness, you should take the lumen value of the old lighting as a starting point. The online calculator above and the comparison table will help you to choose the right LEDs.