Froude, Mach & Weber Numbers

Calculate the Froude, Mach and Weber numbers of a flow from velocity, length, density and surface tension, free online.

Velocity (m/s)

Characteristic length (m)

Fluid density (kg/m³)

Surface tension (N/m; water 0.072) — optional (optional)

Speed of sound (m/s) — optional (optional)

About this calculator

Froude Fr = v ÷ √(gL) compares inertia to gravity (ship waves, open channels); Mach Ma = v ÷ c compares speed to the speed of sound (343 m/s in air at 20 °C); Weber We = ρv²L ÷ σ compares inertia to surface tension (droplets, sprays).