Manning's Equation Calculators

➔ Calculate Manning's Roughness Coefficient
➔ Calculate Flow Velocity
➔ Calculate Hydraulic Radius
➔ Calculate Line Slope

Calculate Manning Roughness Coefficient

n = Manning's Roughness Coefficient
R = Hydraulic Radius
S = Line Slope
V = Flow Velocity

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

Calculate Flow Velocity


V = Flow Velocity
R = Hydraulic Radius
S = Line Slope
n = Manning's Roughness Coefficient

Hydraulic Radius:
Line Slope:
Manning's Roughness Coefficient:
Flow Velocity:
Foot/Second

Calculate Hydraulic Radius


R = Hydraulic Radius
V = Flow Velocity
n = Manning's Roughness Coefficient
S = Line Slope

Flow Velocity:
Manning's Roughness Coefficient:
Line Slope:
Hydraulic Radius:
Foot

Calculate Line Slope


V = Flow Velocity
n = Manning's Roughness Coefficient
R = Hydraulic Radius
S = Line Slope

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

Manning’s Equation is commonly used in open-channel hydraulics to calculate flow parameters such as flow velocity, discharge, or flow area. Here are the calculators based on Manning's Equation:

1. Calculate Manning's Roughness Coefficient (n)

Manning's equation relates the flow rate in an open channel to several physical factors. If you want to calculate the roughness coefficient nn, you can use:

Where:

  • = Flow velocity (m/s)
  • = Manning's roughness coefficient (dimensionless)
  • = Hydraulic radius (m)
  • = Slope of the flow (dimensionless)

To isolate nn, rearrange the equation:

2. Calculate Flow Velocity (V)

Flow velocity can be calculated using the formula:

Where:

  • = Flow velocity (m/s)
  • = Manning’s roughness coefficient
  • = Hydraulic radius (m)
  • = Slope of the flow (dimensionless)

3. Calculate Hydraulic Radius (R)

Hydraulic radius is the ratio of the cross-sectional area of the flow to the wetted perimeter. It is defined as:

Where:

  • = Cross-sectional area of the flow (m²)
  • = Wetted perimeter (m)

4. Calculate Line Slope (S)

The slope SS of the flow is the change in elevation (head) per unit length of the channel, and it can be found from:

Where:

  • = Change in elevation (m)
  • = Length of the flow path (m)