Lumen (lm) is the unit for the total amount of light a lamp emits in all directions.

• The lumen rating on a lamp indicates how much light the lamp can produce, but it does not show how much light actually reaches a surface.

• To determine how much light falls on a particular surface, you use Lux (lx).

In short: lumens tell you the total light output of a lamp, while lux indicates how much of that light is available on a surface.