How many lumens are in a fluorescent light bulb?
The amount of lumens that are emitted from a fluorescent lamp is given approximately by the luminance (cd/m^2) times the length (m) times the diameter (m) times pi squared. Unfortunately, we don’t usually know the luminance. A good rule of thumb is to multiply the rated wattage by 80 (lm/W) to get the number of lumens. A 40 watt fluorescent lamp will output about 3200 lumens.
