The answer to this question depends on the diameter of the tube. 40 watt tubes have diameters ranging from 12″ to 18″, so we’ll assume that you have a tube with a diameter of 16″.

The answer is 4500 lumens. This is because each bulb contains one fluorescent tube, which has a diameter of 16″. The total surface area of a fluorescent light bulb is the sum of all its individual surfaces. In this case, each surface would be the circular cross section of one fluorescent tube. There are two ways to find out how much light is given off by each surface: either calculate it based on how much light it emits per second (lumens), or calculate how much light is received per second by each surface (watts).

We’ll work with lumens first since they’re easier to understand than watts and are more commonly used in lighting applications. Each fluorescent tube has an emission rate of 36 lumens/second at 20°C, which means that for every second that passes, 36 lumens will be emitted by that tube into your room!

Last modified: November 20, 2022