Construction & Materials
Manning's Equation Calculator
Calculate open-channel flow velocity and discharge using Manning's roughness equation.
Your inputs
Change any value to update the result instantly.
Flow velocity
5.7882 ft/s
Discharge Q
46.31 ft³/s
Discharge (gpm)
20,783 gpm
Hydraulic radius
1.2 ft
Formula and working
V = (1.49/n) × R^(2/3) × S^(1/2)
- 1
Collect the inputs
Manning's roughness n = 0.013; Hydraulic radius R = 1.2 ft; Channel slope S = 0.002 ft/ft; Cross-sectional flow area = 8 ft²
- 2
Apply the formula
V = (1.49/n) × R^(2/3) × S^(1/2)
- 3
Result
Flow velocity = 5.7882 ft/s
Frequently asked questions
Important limitation
This is an educational estimate based only on the values and formula shown. Verify current rates, rules, units, and professional standards before relying on the result. It is not personalized financial or investment advice.
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