GPM Flow Rate Calculator
Convert between flow and velocity for water in a pipe. Enter flow and inside diameter to get velocity, or a target velocity to get the flow rate — with a high-velocity warning.
Inputs
From the pipe above, or enter a custom ID
Result
Enter values to calculate
Based on v = 0.4085 × GPM ÷ d² (d in inches). Keep supply-side velocity at or below about 8 fps to limit erosion, noise, and water hammer.
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