Froude Number Calculator
What is a Froude Number Calculator?
A Froude Number Calculator computes the Froude number (Fr), a dimensionless quantity used in fluid dynamics to compare inertial forces to gravitational forces in a flow system. It helps determine whether a flow is subcritical, critical, or supercritical.
The formula is:

Where:
- Fr = Froude number
- V = Flow velocity (m/s)
- g = Acceleration due to gravity (9.81 m/s²)
- L = Characteristic length (e.g., water depth in open channels)
Why is a Froude Number Calculator Important?
- Helps analyze open-channel flow (rivers, canals, spillways)
- Determines flow regimes:
- Fr < 1 (Subcritical Flow): Slow, controlled by gravity
- Fr = 1 (Critical Flow): Transitional state
- Fr > 1 (Supercritical Flow): Fast, dominated by inertia
- Used in ship hydrodynamics to predict wave resistance
- Assists in aerodynamics and hydraulic engineering
How Does It Work?
- Input values for velocity (V) and characteristic length (L).
- Use the formula
- Interpret the result to determine flow behavior.
Example: If water in a canal flows at 3 m/s with a depth of 0.5 m,

Since Fr > 1, the flow is supercritical (fast and turbulent).
When is a Froude Number Calculator Used?
- Hydraulic engineering (dam spillways, river analysis)
- Maritime industry (ship design, wave formation)
- Aerodynamics (airflow analysis in wind tunnels)
- Civil engineering (flood control, drainage systems)