What Are Lumen and Lux?

In the age of efficient LEDs, the lumen indication increasingly replaces the number of watts, which was previously considered the reference value for the brightness of the incandescent lamps. When buying a lamp, it is good to know how much light the lamp radiates exactly. Sometimes this is indicated in lumens or sometimes in lux. What do these values ​​mean and what is the difference?

Lumen (lm)

Lumen is the unit for measuring the visible luminous flux. This indicates the total amount of light emitted from the light source and coming in each direction. In lumens, efficiency is particularly important because it indicates how effectively the light source converts energy to light. This is referred to as the lumen / watt ratio (Lm / W). According to ToughestFlashlights, with LED, this value is much higher because it requires less current to produce a certain lumen current.

Here are some “Watt / Lumen” discussions for the old light bulbs used earlier:

25 W = 220-250 lumens (night light)

40 W = 410-470 Lumen (desk lamp)

60 W = 700-810 Lumen (WC, corridor)

75 W = 920-1060 Lumen (bedroom lamp)

100 W = 1300-1530 Lumen (kitchen lamp, ceiling lamp in living room or study)

Lux (lx)

Lux is used to measure the amount of light output in a given range-one lux is equal to one lumen per square meter. It allows us to measure the total “amount” of visible light and the intensity of illumination on a surface. It is therefore important in which direction the light source is illuminated. This value is independent of the number of light sources used, the color or the structure in which the light is lit. When the amount of Lux is indicated by a lamp, it is usually located in the center of the beam where the light intensity is highest. The required number for a stairs house, for example, is usually 100 Lux and for work centers it is usually 200-700 Lux, depending on the work to be performed.

The difference

The difference between lumen and lux is that Lux takes into account the range over which the luminous flux (lumen) is distributed. A flux of 1000 lumens, concentrated in an area of ​​one square meter, illuminates this square meter with a lighting intensity of 1000 lux.


A 500 lumen light source illuminates 1 square meter with 500 lux. The same light source, which must illuminate 10 square meters, illuminates this area with only 50 lux.