What is lumen?

Lumen is a unit of measure for the amount of visible light emitted by a source. It is defined as the amount of light that is emitted per unit of time and is used to measure the brightness of a light source.

Lumens = Light Output

The higher the number of lumens, the brighter the light source is. Lumen is commonly used to describe the brightness of light bulbs, LED lights, and other sources of light.

Lumen (lm) is the unit for luminous flux.

Nowadays, when buying a lamp, the lumen value is decisive and not the wattage.

Key facts about Lumen:

  • Lumens measure brightness, and watts measure power consumption.
  • Luminous efficacy: measures the efficiency of a lamp in lumens per watt; the higher the value, the more efficient a lamp is
  • The ideal lumen value depends on many factors: room size, ceiling height, task areas, and color selection.

Lumen Calculator

Lumen Calculator

Lumen Calculator

Enter the wattage of your bulb:

Enter the luminous efficacy (lumens per watt):


What is the difference between lumens and watts?

The watt unit collects electrical power and does not provide any information about the amount of light emitted. Watt says something about the power consumption of a lamp. Lumen is the relevant comparison value for determining the brightness – because you want to know how much visible light your lamp actually emits. The various light sources, such as halogen and energy-saving lamps, emit a different amount of luminous flux for each watt. Basically, the higher the number of lumens, the more brightness the light source offers.

Lumens per watt: the light output

The luminous efficacy is the physical quantity that is used to measure the efficiency of a lamp. The lumen per watt (lm / W) value indicates how much of the required energy is converted into light. With a high value, the light output is more efficient than with a low one.

Converting watts to lumens made easy

Lumen helps you find the amount of lamps you need to optimally illuminate a room. Here you can see which lumen value corresponds to a wattage:

15 W90120125135
25 W220215230250
40 W415410430470
60 W710700740800
75 W9359209701055
100 W1340132014001520
150 W2160214022502450

Which lumen value do I need?

How many lumens you need depends on several factors: size and layout of the room, height of the ceiling, type of light source, task areas, color scheme and your individual needs. The following values ​​will help you to orientate yourself when planning lighting:

AreaLumens per
square meter
kitchen 300-400
living room 400-500
bedroom 300-400
bathroom 500-600
Workspace 280
Hallway 300
Would you like to replace your lightbulbs at home with energy-efficient alternatives without losing brightness? Simply add up the lumen value of the "old" light sources. So you have an overall value that can be covered by economical LEDs. At the same time, the number of watts and thus your energy consumption is reduced.