NPSH Available Calculator
Net positive suction head available at the pump eye, from atmospheric pressure, lift, friction and vapour pressure.
Every metre of suction lift and every degree of temperature eats NPSHa. ANSI/HI 9.6.1 recommends margin ratios of 1.1โ2.5ร depending on service.
Formula
NPSH Available Calculator is a free npsh available for pump engineers, plumbers and plant designers โ instant, accurate and 100% client-side, with the governing formula and reference shown next to the result so the number can be defended, not just quoted.
About NPSH Available Calculator
Net positive suction head available at the pump eye, from atmospheric pressure, lift, friction and vapour pressure. The calculation implements NPSHa = P_atm/ฯg โ H_lift โ h_f โ P_v/ฯg (ANSI/HI 9.6.1 โ NPSH margin). Every metre of suction lift and every degree of temperature eats NPSHa. ANSI/HI 9.6.1 recommends margin ratios of 1.1โ2.5ร depending on service.
How to use NPSH Available Calculator
- 1Enter Atmospheric pressure in kPa(a).
- 2Enter Static lift (+below pump) / submergence (โ) in m.
- 3Enter Suction friction loss in m.
- 4Enter Vapour pressure in kPa(a) (Water: 20 ยฐC = 2.34 ยท 60 ยฐC = 19.9 ยท 90 ยฐC = 70.1).
- 5Read NPSH available, Margin over NPSHr instantly โ no submit button needed.
- 6Need US units? Flip the SI/Imperial toggle and every field converts.
Why use NPSH Available Calculator?
- โImplements the standard formula โ NPSHa = P_atm/ฯg โ H_lift โ h_f โ P_v/ฯg
- โReference cited on-page: ANSI/HI 9.6.1 โ NPSH margin
- โOne-click SI โ Imperial toggle โ values convert in place, physics stays in SI
- โLive worked example: the substitution recomputes from your numbers
- โBuilt-in engineering verdict flags out-of-range results instantly
- โRuns entirely in your browser โ nothing uploaded, free forever
Frequently asked questions
What formula does the NPSH Available Calculator use?+
It computes NPSHa = P_atm/ฯg โ H_lift โ h_f โ P_v/ฯg, per ANSI/HI 9.6.1 โ NPSH margin. The formula is displayed under the result along with a worked example substituted with your own inputs.
What should I keep in mind when using this calculator?+
Every metre of suction lift and every degree of temperature eats NPSHa. ANSI/HI 9.6.1 recommends margin ratios of 1.1โ2.5ร depending on service.
Can I use this for pump selection?+
Use it to establish the duty (flow, head, NPSH, power) and then pick a pump whose curve passes through that point near best efficiency. The tool gives you the engineering numbers a supplier will ask for.
Is the NPSH Available Calculator free to use?+
Yes โ completely free, no sign-up, no limits. It runs client-side in your browser, so inputs stay private and results are instant even on slow connections.
Related Engineering tools
Reynolds Number Calculator
Compute Re from density, velocity, pipe diameter and viscosity โ with instant laminar/turbulent classification.
โ LiveLaminar vs Turbulent Flow Classifier
Classify hydraulic-oil or process-fluid flow regime from kinematic viscosity, line velocity and tube bore.
โ LiveBernoulli Equation Solver
Solve downstream pressure between two points from velocities, elevations and fluid density (ideal, lossless).
โ Live