Lumens (lm) are a measure of the total amount of visible light (to the human eye) from a light bulb or light source. The higher the lumen rating the “brighter” the lamp will appear. Simply put, lumens = light output.
We have all bought 50W or 60W conventional bulbs or spotlights in the past expecting a certain level of brightness. This incorrectly linked power consumption (Watts) to light output. With low energy LED lamps, more light output can be achieved with much less power consumption. For example, a 6.5W LED lamp will give a similar light output to a 50W Halogen bulb. That's 87% less energy for the same light output! When using LED, more energy is converted to light rather than heat. As technology improves, more lumens will be produced using even less Watts - i.e. more lumens per Watt. So as a result, using Watts as a guide to brightness is no longer relevant.
For non-directional bulbs such as a globe, golf ball or candle shape, the total lumen output is calculated for all directions. With a directional bulb such as GU10 spotlight, the light is emitted in many directions, some of this light (spill light) may not be useful but it is counted in the total lumen rating.
How many lumens you need will depend on several factors including room size and shape, height of ceilings, colour scheme, type of light bulb and fitting, task areas and needs of the user.
As a basic guide, below are the lumens required per sq m (10.76 sq ft) for different room settings. In many cases a mixture of general and task lighting will be required.
