How NPSH Calculator Works
Estimate net positive suction head available from pressure head, elevation, velocity and vapor pressure. The calculation runs locally in your browser and does not require an account.
How to use it
- Enter values using the units shown.
- Check your source measurements and assumptions.
- Calculate and compare scenarios before making a decision.
Limitations
NPSH Calculator is an estimation aid. For a critical result, compare the inputs and output with the applicable standard, manufacturer data, project specification, site condition, or qualified professional review.
Understanding NPSH
Net positive suction head is a pump-system quantity used to assess whether liquid pressure at the pump inlet is sufficient to avoid excessive vapor formation. The available value depends on the liquid pressure at the suction point, elevation, velocity and losses in the suction piping, and the liquid's vapor pressure at its operating temperature. Because vapor pressure changes with temperature and fluid composition, a result that looks acceptable for water at one temperature may not apply to another fluid or condition.
Use this calculator for preliminary comparisons between operating scenarios. For a real pump installation, compare NPSH available with the pump manufacturer's NPSH required curve and include the design margin required by the project. Check transient conditions, minimum tank level, suction-line fittings, strainers and valves rather than relying on a single steady-state number.