Manning Formula

Manning Formula (SI System） (fps System)

where:
V – Velocity (ft/s);
R – Hydraulic radius in ft;
R = area / wetted perimeter;
n – Manning roughness coefficient;
S – slope of the energy grade line (head loss per unit length of conduit or pipe.

Manning Formula (SI System） (SI System)

where:
V – Velocity (m/s);
R – Hydraulic radius in m;
n – Manning roughness coefficient;
S – slope of the energy grade line (head loss per unit length of conduit or pipe.