NPSH Available Calculator
Calculate available suction head above liquid vapor pressure from reservoir pressure, elevation and entered suction losses.
YOUR CALCULATION
Result
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Calculation steps
Work through one step at a time or reveal the complete calculation. The steps use your current inputs.
How to calculate
Apply the reservoir-to-pump Bernoulli head balance and subtract vapor-pressure head. Positive elevation is above the pump datum.
NPSHa=(surface absolute pressure−vapor pressure)/(ρg)+surface elevation−suction head loss
Worked example
At 101.325 kPa surface pressure and 2.34 kPa vapor pressure, 1000 kg/m³ density, 2 m elevation and 1 m loss, NPSHa is about 11.0936609 m.
Assumptions and input details
Large reservoir with negligible surface velocity, constant density and entered operating-temperature vapor pressure. No required NPSH or cavitation margin is inferred; manufacturer curves and transient conditions are outside this calculation.
References: University of Florida: pump suction-head balance
Unit definitions
Unit selection is independent of language. Each selector contains only units for its physical quantity. Calculations use defined base units internally.
Choose from 23 length definitions, including explicitly labelled regional measures. Area conversions square the length factor; geometric volumes cube it.
Regional measures are not interchangeable merely because their names look similar. This is a documented selection, not a claim to include every historical unit.
NIST measurement tables · Japanese traditional units · Mainland China and Hong Kong unit distinctions
Using this calculator
Can I enter my own problem?
Yes. Replace the example values with your own inputs. The result, calculation steps, tables and applicable diagrams update from those inputs. Blank or invalid values clear the result; example values are never silently substituted for missing inputs.
Are the results exact?
Results use floating-point arithmetic and displayed rounding. Read the formula, assumptions and any stated data precision before interpreting the result.
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The calculation runs in your browser. No account, file upload or external AI service is required. Inputs are not saved between page reloads.
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