How to use the manning channel velocity calculator
Compute open channel flow with Manning's equation. Enter manning n, hydraulic radius, channel slope in the fields above; the velocity is computed instantly and plotted on the chart so you can see how the answer changes.
Formula
Variables
- n — Manning n
- R — Hydraulic radius (m)
- S — Channel slope
Worked example
With manning n = 0.03, hydraulic radius = 0.5 m, channel slope = 0.002, the calculator gives velocity ≈ 0.9390897 m/s.
Frequently asked questions
What is the formula for the manning channel velocity calculation?
Velocity (m/s) = R^(2 / 3) × √(S) / n. Here n is manning n, R is hydraulic radius (m), S is channel slope.
What inputs do I need for the manning channel velocity calculator?
You need manning n, hydraulic radius in m, channel slope. Each field is pre-filled with a typical example so you can see how the result responds as you edit the numbers.
How do I use this calculator?
Type values into the input fields. Results and the chart update instantly. Use Reset to restore the example values, Copy results to paste them elsewhere, or Share to copy a link that preserves your inputs.
Is the result exact?
Calculations use standard formulas and double-precision arithmetic, then display about seven significant figures. Real-world measurements carry uncertainty, so treat results as estimates unless your inputs are exact.