Free Online Manning Pipe Flow Calculator

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Manning Formula Uniform Pipe Flow at Given Slope and Depth

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Flow, Q (See notes) Flow, Q (See notes) X
Velocity, v Velocity, v X
Velocity head, hv Velocity head, hv X
Flow area Flow area X
Wetted perimeter Wetted perimeter X
Hydraulic radius Hydraulic radius X
Top width, T Top width, T X
Froude number, F Froude number, F X
Average shear stress (tractive force), tau Average shear stress (tractive force), tau X


This is the flow and depth inside the pipe.
Getting the flow into the pipe may require significantly higher headwater depth. Add at least 1.5 times the velocity head to get the headwater depth or see my 2-minute tutorial for standard culvert headwater calculations using HY-8.

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