Culvert Sizing Calculator
Size circular culverts by checking inlet and outlet control headwater depths. Determines if a selected pipe size is adequate for the design flow.
Inputs
cfs
ft
ft
ft
ft/ft
Results
Selected Pipe Diameter
36 in
Design Adequate
0
Inlet Control HW8 ft
Outlet Control HW2.74 ft
Outlet Velocity7.07 ft/s
How to Use This Calculator
- Enter design flow (cfs), allowable headwater depth (ft), and tailwater depth (ft).
- Set culvert length (ft) and slope (%).
- Review Required Diameter (inches) and inlet control headwater depth.
- Round up to the next standard pipe size and verify both inlet and outlet control conditions.
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