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

**What is water flow?**

Water flow is a measure the volume of water moving through an opening per unit of time.