Lamps used for lighting are commonly labeled with their light output in lumens; in many jurisdictions this is required by law. For LED Light Bar technology this measure of light is fast becoming the standard. 

A 23 watt compact fluorescent lamp emits about 1500-1600 lm.

On 1 September 2010, European Union legislation came into force mandating that lighting equipment must be labeled primarily in terms of lumens, instead of watts of electricity consumed.

Lumen (unit), the SI unit of luminous flux. The lux (symbol: lx) is the SI unit of luminance and luminous emittance, measuring luminous flux per unit area. It is used in photometry as a measure of the intensity, as perceived by the human eye, of light that hits or passes through a surface. It is analogous to the radiometric unit watts per square meter, but with the power at each wavelength weighted according to the luminosity function, a standardized model of human visual brightness perception. In English, "lux" is used in both singular and plural.


Luminance is a measure of how much luminous flux is spread over a given area. One can think of luminous flux (measured in lumens) as a measure of the total "amount" of visible light present, and the luminance as a measure of the intensity of illumination on a surface. A given amount of light will illuminate a surface more dimly if it is spread over a larger area, so luminance is inversely proportional to area.

One lux is equal to one lumen per square meter:

1 lx = 1 lm/m2 = 1 cd*sr*m-2.

A flux of 1,000 lumens, concentrated into an area of one square meter, lights up that square meter with an luminance of 1,000 lux. However, the same 1,000 lumens, spread out over ten square meters, produce a dimmer luminance of only 100 lux.

Achieving an luminance of 500 lux might be possible in a home kitchen with a single fluorescent light fixture with an output of 12,000 lumens. To light a factory floor with dozens of times the area of the kitchen would require dozens of such fixtures. Thus, lighting a larger area to the same level of lux requires a greater number of lumens.

As with other SI units, SI prefixes can be used, for example a kilolux (klx) is 1,000 lux.