# 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 EGL 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 Average shear stress (tractive force), tau Average 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 EGL Upstream EGL m H2O mm H2O kPa ft H2O in H2O psi X Upstream HGL in pipe (See notes) Upstream HGL in pipe (See notes) m H2O mm H2O kPa ft H2O in H2O psi X

Notes:

For an open inlet (culvert) condition, 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.