Watts or lumens – how do I work out how bright bulbs are?

Hello, my name is Anita, and welcome to Paulmann's World of Light on YouTube. When buying light bulbs, do you ever wonder whether it is watts or lumens that indicate how bright they are? Today I will explain the way you can tell how bright a bulb is and how to find the suitable replacement for your worn-out incandescent light bulbs.

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watt = physical unit of power

I'm often asked whether the wattage shows how bright a bulb is. This is because that was the case when using the old incandescent light bulbs. Until a few years ago incandescent light bulbs were the most popular form of lighting. At that time watts were used to show brightness. But they are actually a physical unit of power, in other words the power consumption of a bulb. For incandescent light bulbs, the brightness depended on the power: the more watts, the more light it gave out.

Paulmann lamps

Thus, for incandescent bulbs a comparison was actually given in watts. Replacements for incandescent light bulbs, such as this 33 W halogen bulb, this 9 W energy-saving bulb and this 5 W LED, all produce the same brightness as this 40 W incandescent light bulb, despite having different wattages.

As you can see, the wattage is no longer useful for comparing the brightness of different types of bulb.

Lumen (lm) = unit of measurement for luminous flux

The explanation for this is quite simple: new, modern bulbs require less electricity than incandescent light bulbs to achieve the same luminous power. The most efficient bulbs at the moment are LEDs.  

In terms of brightness, the crucial value is lumen. This is the unit of measurement for luminous flux, in other words the amount of light that a bulb emits. Therefore, lumens rather than watts show how bright a bulb is.

Wie finde ich eine LED mit der gleichen Helligkeit wie meine ausgediente Glühbirne?

Multiply the wattage of your old incandescent light bulb by 10 to get a rough lumen value for a more efficient LED lamp to replace it with.

But how do I find an LED with the same brightness as my old incandescent light bulb? And what is the equivalent of the wattage I have been using up to now in lumens?

There is a really easy trick to work this out. Multiply the wattage of your old incandescent light bulb by 10 to get a rough lumen value for a more efficient LED lamp to replace it with. However, this only works for LED omnidirectional lamps, meaning those in the traditional light bulb shape.

We'll use this 40 W incandescent light bulb as an example: 40 times 10 = 400. For the same brightness you'll need a 400 lumen bulb.

LED saves 80%

Let's compare it with this 470 lumen LED bulb. The human eye perceives no difference in brightness. But the LED only uses 5 W instead of 40. This reduces energy consumption by well over 80%.

You can find the lumen specifications and the comparison with watt value for incandescent light bulbs on all Paulmann packaging. The relevant conversion table for the bulb you want can also be found on the shelves in Paulmann hardware or furniture shops, on the Paulmann homepage and on flyers.

conversion table  Watt - Lumens

In this episode, I have shown you that a bulb's brightness can be determined from the lumen value. I have also demonstrated an easy way to calculate the lumen value for a new bulb using the wattage of an old incandescent light bulb.

So the next time you have to buy a light bulb you shouldn't have any problems. Best of luck in choosing the right bulb! Until next time,


video colour temperature

I also recommend watching our video on the topic of colour temperature. In this video I explain what colour temperature means and how you can use it to achieve specific effects.

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