The diameter of a pipe is the distance between the inner edges of the pipe. It is an important measurement to take when working with pipes, as it can affect the flow rate of fluids through the pipe. There are a few different ways to measure the diameter of a pipe, depending on the size and shape of the pipe.
For small pipes, you can use a ruler or tape measure to measure the outside diameter of the pipe. Then, subtract the thickness of the pipe wall to get the inside diameter.