Cavitation Number Calculator

Calculate cavitation number from local pressure, vapor pressure, density, and velocity.

σc = (p − pv) / (½ρv²)

Local absolute pressure p (Pa)

Vapor pressure pv (Pa)

Density ρ (kg/m³)

Velocity v (m/s)

Enter valid values in all required fields.

What this formula means

Cavitation number measures the pressure margin above vapor pressure relative to the flow dynamic pressure. Lower values generally mean a greater risk that vapor cavities will form and collapse.

Use it for propellers, hydrofoils, pumps, valves, spillways, turbines, and high-speed liquid flows. The result should be interpreted with consistent units and with the assumptions of the underlying model in mind.

Worked example

Water near room temperature at 10 m/s and atmospheric pressure gives a cavitation number close to 1.98.

Applications

Use it for propellers, hydrofoils, pumps, valves, spillways, turbines, and high-speed liquid flows. It is also useful as an independent check when comparing hand calculations, laboratory measurements, simulations, or preliminary engineering estimates.

Assumptions and common mistakes

Important: Use absolute pressure and the vapor pressure at the actual liquid temperature. Gauge pressure cannot be inserted directly.

Use SI units unless the field label states otherwise. Keep significant figures appropriate to the accuracy of the inputs, and do not treat a simplified calculator as a replacement for codes, detailed design standards, or professional review.

Frequently asked questions

What equation does this calculator use?σc = (p − pv) / (½ρv²). The calculator evaluates the displayed relationship using the values entered above.

Are the results unit-sensitive?Yes. The input labels use SI units so the displayed output follows the corresponding SI unit.

Can I use this for engineering design?Use it for learning and preliminary checks. Final designs require validated data, applicable standards, safety factors, and professional judgment.