Lumen (lm) is the unit of luminous flux. Lumen indicates the total amount of light emitted by a light source per unit of time (second), regardless of in which direction.

 

LED lamps or luminaires always refer to a certain wattage and number of Lumen.

 

The quality of an LED chip differs in many cases, so it may be that 2 lamps of the same wattage still emit a different number of lumens.

 

Lumen is therefore a better indication of light output than wattage, as wattage only tells how much a bulb consumes.