Watts and Lumens

Watts and Lumens: What Is the Difference?



 – Watts and Lumens: light output and conversion

 – Watts and lumens: correspondence table

 – Some facts about “new generation” light bulbs


You knew the watts (W). With the advent of light-emitting diodes, another unit of measurement is used, the lumen. Where watts measure the electrical power consumed, lumens directly measure the light output.

So what does this mean in practice?

Watts and lumens: what is the difference?

To choose the power of our lighting, until 2006, we looked at the number of watts indicated on the packaging of a bulb:

 – The more powerful the light, the more energy was consumed and the higher the number of watts.

 – Now, however, new light bulbs can produce much more light with much less energy consumption:

 ◦ They are called “compact fluorescent” because they produce light by exciting a fluorescent molecule.

 ◦ Basically, this molecule can absorb energy and release it as light.

 ◦ Fluorescent light uses much less energy than the light produced by conventional incandescent lamps, which produce their light by heating a metal filament.

 ◦ In fact, CFLs heat up much less.

 – The energy consumed is, therefore, no longer a sufficient criterion for measuring the power of a bulb.

 – The lumen is a direct measure of the light emitted by a lamp.

 – The abbreviation for lumen is “lm”.

Watts and lumens: correspondence table

Watts and Lumens

To go from watt to lumen smoothly, here is a table of correspondence between the watts of traditional bulbs with filament and the lumens of the bulbs “new generation”:


15 W

25 W

40 W

60 W

75 W

100 W

150 W

200 W


130 lm

240 lm

440 lm

750 lm

990 lm

1 420 lm

2 290 lm

3 220 lm

If you don’t have your correlation chart with you and can’t look it up using your smartphone, here’s a tip:

 – 1 W is worth about 10 lm.

 – You should be fine either way:

 ◦ multiplying the number of watts you are looking for by 10 to get the approximate value in lumens;

 ◦ dividing the number of lumens listed by 10 to get the approximate value in watts.

Some facts about “new generation” bulbs

The new compact fluorescent bulbs:

 – are not to be disposed of in regular household waste: take them to stores that sell them, otherwise drop them off at a waste electronics collection service;

 – can rarely be used with a conventional dimmer switch;

 – take a long time to reach maximum brightness: be aware that there are improved compact fluorescent lamps;

 – They are more expensive, but their start-up time is almost as fast as other types of lamps.

In places where the lamps will be regularly switched on and off, do not use conventional CFLs, as they may have a short life due to the many switching operations (on, off).

Choose compact fluorescent lamps that can withstand up to one million switches or those for which the number of switches is unimportant. The maximum number of switches a lamp can handle is specified on the package.

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Watts and Lumens: What Is the Difference?

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