# Manning's Equation Calculators

Calculate Manning Roughness Coefficient

n=[1.49×R^0.66×S^0.5]/V
n = Manning's Roughness Coefficient
S = Line Slope
V = Flow Velocity

Line Slope:
Flow Velocity:

Result:

Manning's Roughness Coefficient:

Calculate Flow Velocity

V=[1.49×R^0.66×S^0.5]/n
V = Flow Velocity
S = Line Slope
n = Manning's Roughness Coefficient

Line Slope:
Manning's Roughness Coefficient:

Result:

Flow Velocity:
Foot/Second

R=([V×n]/[1.49×S^0.5])^[1/0.66]
V = Flow Velocity
n = Manning's Roughness Coefficient
S = Line Slope

Flow Velocity:
Manning's Roughness Coefficient:
Line Slope:

Result:

Foot

Calculate Line Slope

S=([V×n]/[1.49×R^0.66])^2
V = Flow Velocity
n = Manning's Roughness Coefficient
S = Line Slope

Flow Velocity:
Manning's Roughness Coefficient:

Result:

Line Slope:

Manning's Equation Calculators

Manning's formula refers to the empirical formula of open channel flow or velocity, which is often used in physical calculations, water conservancy construction and other activities. Manning's formula is a formula with a wider range of applications, but if the fluid in the open channel is a constant uniform flow and a constant slowly varying flow in the open channel, we can use the simpler form of Sheetsa's formula to calculate the flow rate.

Manning's formula: Empirical formula for open channel flow or speed. where v is the velocity;
k is the conversion constant with a value of 1 in the SI unit;
n is the roughness, which is a coefficient that comprehensively reflects the impact of the roughness of the pipe and channel wall on the water flow. Its value is generally measured by experimental data, and can be selected by looking up the table when using it. There are some useful n values to choose from in the extended reading URL:
Rh is the hydraulic radius, which is the ratio of the fluid cross-sectional area to the wetted perimeter. The wetted perimeter refers to the perimeter where the fluid is in contact with the open channel section, excluding the perimeter that is in contact with the air;
S indicates the slope of the channel.

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