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Pumps
NPSH Calculator
Enter values in the stated units. Example inputs are provided to help you explore the method.
Results
Your results will appear here after calculation. Changing an input clears the previous result.
Method & assumptions
- Reservoir model: NPSHA = (surface absolute pressure − vapor pressure)/(density × g) + liquid elevation − suction losses; negligible reservoir velocity
- Uses the required NPSH entered from the manufacturer curve; it cannot be inferred from suction conditions
- Returns the arithmetic margin NPSHA minus the supplied NPSHR. A positive margin alone does not establish cavitation-free operation or an adequate application-specific margin.
- Check the pump curve at the actual flow and speed and confirm its cavitation criterion. NPSH3 refers to a 3% head-drop criterion, not the onset of cavitation. Include suction entry, valve and fitting losses.