Lumen (lm) is the measure of power of light perceived by the human eyes.

A shortcut light bulb manufacturers use to explain the light output of CFLs and LED light bulbs is based on the wattage of incandescent light bulbs that produce certain amount of light output, in which CFLs or LED light bulbs to replace can produce similar amount of light output.

Below table shows different wattage of incandescent light bulbs and light output (in lumens) these light bulbs produce (*light output shown in table is dependent on light efficiency of incandescent light bulbs):