To use a watts-to-lumens conversion table or calculator, such as those at RapidTables.com or MGE.com, find the type of light source on the table or calculator, and then find the lumens associated with the wattage rating for the light source. The brightness of a light source, often measured in lumens, depends on many factors including the light source's type, color and power rating, which is typically measured in watts.
At MGE.com, click the Saving Energy tab near the top of the main page, and then click Lighting beneath the Saving Energy heading near the top-left of the page. Click the Lumens-per-Watt Comparison link beneath the Compact Fluorescent Bulbs section midway down the page to display a chart. Find your light source type on the horizontal scale; the bar above it depicts the typical range of brightness in lumens per watt of power your light source uses.
At RapidTables.com, click Lighting Calculators beneath the Online Calculators heading near the top-left of the main page, and then click Watts to Lumens Calculator beneath the Calculators heading near the top-left of the page. Type the wattage rating of the light source in the Enter Power in Watts box, select the type of light source on the Enter Light Source drop-down menu, and then click the Calculate button to display the brightness of the light sources in lumens.