Enter the water velocity and diameter of the pipe into the calculator. The calculator will evaluate the volume flow rate of the water moving through the pipe.
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Water Flow Rate Calculator
The following equation is used to calculate the volume flow rate of water moving through a pipe given the velocity and pipe diameter.
Q = D^2 * V / .408
- Where Q is the volume flow rate in gal/min
- D is the diameter in inches
- V is the velocity ft/s
To calculate the water flow rate, square the diameter, multiply by the linear velocity, then divide by .408.
Water Flow Rate Definition
Water flow rate is typically either a rate of mass or volume of water that is moving through a pipe. In this case, the equation above solves for gallons per minute.
Water Flow Rate Example
How to calculate water flow rate?
- First, determine the diameter of the pipe.
Measure the diameter of the pipe.
- Next, determine the velocity of the flow.
Measure the water flow velocity.
- Finally, calculate the water flow rate.
Using the formula above, calculate the flow rate in gal/min.
FAQ
Water flow is a measure the volume of water moving through an opening per unit of time.

