We get asked allot how lumens relate to wattage, all lamps have always been rated in wattage, because they have been around for so long people know how bright 60 watts is, but as soon as the manufactures started advertising the lumen output of their lamps it confused people.
Bellow is the basic lumen output of standard non energy saving lamps
Incandescent lamps = Average 10 lumens per watt
Halogen lamps = Average 15 lumens per watt
So a 100 watt standard lamp ( 100 x 10 = 1000 lumens) This is basically how it works.
Below is a far more detailed explanation of lumens to watt
The lumen (symbol: lm) is the SI unit of luminous flux,
a measure of the perceived power of light. Luminous flux differs from radiant flux, the measure of the total power of light emitted, in that luminous flux is adjusted to reflect the varying sensitivity of the human eye to different wavelengths of light. The lumen is defined in relation to the candela by
1 lm = 1 cd•sr = 1 lx•m2
That is, a light source that uniformly radiates one candela in all directions radiates a total of 4π lumens. If the source were partially covered by an ideal absorbing hemisphere, that system would radiate half as much luminous flux—only 2π lumens.
*If a light source emits one candela of luminous intensity uniformly across a solid angle of one steradian, its total luminous flux emitted into that angle is one lumen. Alternatively, an isotropic one-candela light source emits a total luminous flux of exactly 4π lumens. The lumen can be thought of casually as a measure of the total "amount" of visible light in some defined beam or angle, or emitted from some source.
A standard North American 100 watt incandescent light bulb emits 1500–1700 lumens, while a standard European 230 V model emits 1200–1400 lm.
A 100 watt high-pressure sodium vapour lamp emits around 15,000 lumens.
*The watt (symbol: W) is the SI derived unit of power, equal to one joule of energy per second. It measures a rate of energy use or production.