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How to Convert GPM to FPS

When calculating the flow of water in a pipe, scientists and engineers convert the amount of water traveling during a given time frame to a speed. For example, if you calculated the flow of water to be 34 gallons per minute (GPM), you can convert that to feet per second (FPS). You will need to know variables such as the area of the object the water is running through. But that sounds more complicated than it is in practice. With a little effort and some simple math, the conversion can be done quickly.

Instructions

- 1
  Convert GPM into cubic feet by multiplying by .1337. For example; 34 GPM x .1337 = 4.54 cubic feet per minute.
- 2
  Examine the object the water is flowing through. In most instances, it will be a metal pipe, such as those used in sewers. Calculate the cross-sectional area of the pipe in square feet. The formula for the cross-sectional area of a pipe is Pi/4 (outside diameter - inside diameter.) For example; the cross-sectional area of a pipe with an outside diameter of 4 feet and inside diameter of 2 feet would be 3.14/4 (4-2) = 1.57 square feet.
- 3
  Divide the cubic feet measurement by the cross-sectional area to get linear feet per minute. For our example; 4.54/1.57 = 2.89 feet per minute.
- 4
  Convert feet per minute into feet per second by dividing by 60. In our example; 2.89 / 60 = .048 FPS.

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