# Free Online Manning Pipe Head Loss Calculator

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## Manning Formula Head Loss at Given Full Flow

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Inputs
 Flow, Q (See notes) m^3/s l/s Ml/d cfs gpm MGD X Pipe diameter, d0 m mm ft in X Pipe length, L m mm ft in X Manning roughness, n ? X Total combined junction loss coefficient, k X Downstream HGL m H2O mm H2O kPa ft H2O in H2O psi X
Results
 Area, A Area, A m^2 mm^2 ft^2 sq. in. X Wetted perimeter Wetted perimeter m mm ft in X Hydraulic radius Hydraulic radius m mm ft in X Velocity, v Velocity, v m/s ft/sec X Velocity head, hv Velocity head, hv m H2O mm H2O kPa ft H2O in H2O psi X Friction slope Friction slope rise/run % rise/run X Shear stress (tractive force), tau Shear stress (tractive force), tau N/m^2 psf X Friction loss, Hf Friction loss, Hf m H2O mm H2O kPa ft H2O in H2O psi X Junction loss, Hm Junction loss, Hm m H2O mm H2O kPa ft H2O in H2O psi X Total loss, Hl Total loss, Hl m H2O mm H2O kPa ft H2O in H2O psi X Upstream HGL (See notes) Upstream HGL (See notes) m H2O mm H2O kPa ft H2O in H2O psi X Upstream EGL (See notes) Upstream EGL (See notes) m H2O mm H2O kPa ft H2O in H2O psi X

Notes:

It is necessary to check for inlet control conditions.
1. The upstream HGL cannot be lower than the upstream normal depth flow elevation (or lower than the pipe!).
2. The headwater of a culvert is better represented by the upstream EGL than the upstream HGL.
3. See my 2-minute tutorial for simple standard culvert headwater calculations using HY-8.