# What are some examples of light bulbs

## Lumen: A unit for the luminous flux

### Lumens - what is it?

Lumen (lm) is the standardized unit for the so-called Luminous flux and allows conclusions to be drawn about the brightness of a lamp. The luminous flux indicates how much light a light source emits in all directions. Colloquially, one also speaks of the light output of a lamp. Using the lumen rating, consumers can estimate how bright a lamp is: the higher the lumen value, the more light a lamp emits per unit of time.

Different light sources such as incandescent lamps, energy-saving lamps and LED lights produce very different luminous fluxes per watt. When light bulbs were still used almost exclusively for lighting in the home, their brightness was easily recognized by the power consumption in watts. But now manufacturers have to specify how many lumens a lamp emits.

### Scientific definition lumen

Lumen is the internationally standardized unit of measurement for the luminous flux of a light source. The luminous flux indicates the amount of light generated per unit of time; the time unit is due to the speed of light of 300,000 km / second quasi = 0, since the speed of light forms our perception limit.

### Lumen: what is light?

To get a feel for how many lumens a lamp has, here are some examples:

• a 40 watt (W) fluorescent lamp = about 3,000 lm
• a 100W light bulb = about 1,340 lm
• one candle = about 12 lm

However, the examples mentioned are less informative today than they were a decade ago, because light bulbs and fluorescent lamps are used less and less.

The watt unit provides information on how powerful a lamp is and how much electricity it consumes. When there were only light bulbs, a look at the wattage was enough to be able to draw conclusions about the brightness of a lamp. At that time, the rule of thumb was: the more watts that are shown, the brighter the lamp shines.

### How many lumens does a light bulb have?

The following luminous flux values ​​apply to light bulbs:

• 25W light bulb = approx. 220 lm
• 40W light bulb = approx. 415 lm
• 60W light bulb = approx. 710 lm
• 100W light bulb = approx. 1,340 lm

With the variety of lamp types nowadays, you should rather take a look at the lumen specification of the lamps. Because in the meantime lamps are a lot more efficient and require significantly less watts in order to be able to shine even brighter than the earlier lightbulbs. A high-quality LED lamp, for example, can produce a much higher luminous flux than an incandescent lamp with the same energy consumption. The wattage indicated on the packaging is now primarily used as information about energy consumption.

The EU has summarized the equivalent lumen values ​​of different types of lamps compared to the old incandescent lamp (Regulation EC No. 244/2009 of the Commission of March 18, 2009) in a table:

### Luminous efficiency: How many lumens corresponds to how many watts?

When considering the luminous flux of a lamp in combination with its output, one quickly arrives at another physical quantity: the luminous efficacy. The light output is measured in lumens per watt (lm / W) and indicates how efficiently a lamp shines. The light yield can be used to read how much energy is converted into light. The higher the value, the more efficient a light source can be classified.

As a guide for the light output, you can roughly use the following values:

• Light bulb: approx. 10 lm / W
• Halogen lamp: approx. 20 lm / W
• Fluorescent lamp: approx. 70 - 90 lm / W
• LED lamp: approx. 60 - 170 lm / W

### Where do you need how many lumens?

How many lumens should you plan for per square meter in order to illuminate your home optimally and comfortably?

The need for brightness depends primarily on the needs of the residents and the activities that take place in this room. In rooms such as the kitchen or the study, a greater amount of light is required in order to cook or work without any problems. The living room, on the other hand, is primarily used for relaxation: it should be cozy here, bright light is hardly needed. You can also find details on the topic in this post: "Interior lighting: function, planning and implementation".

You can use the following rough guide values ​​for optimal brightness in the various rooms of your home:

• Kitchen: about 280 lumens per square meter (lm / m2)
• Bath: about 280 lm / m2
• Bedroom: about 140 lm / m2
• Living room: about 140 lm / m2
• Nursery: about 140 lm / m2
• Workspace: about 280 lm / m2
• Hall: about 140 lumens lm / m2

For example, if you want to pleasantly illuminate a 30 square meter living room, your lamps should generate a luminous flux of around 4,200 lumens (30 square meters x 140 lm = 4,200 lm).

### Can you just add lumens?

Yes, the values ​​of different lamps can simply be added up. For example, if you want to replace the light sources in your living room with economical LEDs without sacrificing brightness, you can add the individual lumen values ​​of the "old" light sources. This results in a lumen value that can now also be covered by energy-efficient LEDs.

### An example: swapping light sources for LEDs in the living room

The following lights are available in the living room:

• Ceiling lamp with four halogen spots GU10, 50 watts each 330 lm
• Floor lamp with energy-saving lamp E27, 20 watt, 1,140 lm
• table lamp with halogen E14, 40 watts at 260 lm

So far, the lamps in the living room could generate a luminous flux of 4 x 330 lm + 1,140 lm + 260 lm = 2,720 lm.

After replacing the light sources with efficient LEDs, a luminous flux of 3,371 lm could be achieved in the living room. The possible solution to this:

• Ceiling lamp with four LED GU10, 5.5 watts, each 345 lm
• Floor lamp with LED E27, 15 watt at 1,521 lm
• table lamp with LED E14, 6 watt at 470 lm

At Lampe.de you will find lights for your living rooms and the outdoor area.