MAXScanner engineering calculator
NPSH Available Calculator — Pump Suction Margin
Calculate pump net positive suction head available from absolute suction pressure, vapor pressure, density and suction velocity.
Last updated: September 17, 2026
Results
Require suction pressure ≥ vapor pressure, positive density and non-negative velocity
Formula, example and assumptions
NPSHa=(Ps−Pv)/(ρg)+v²/(2g).
Ps=200 kPa abs, Pv=3 kPa, ρ=998 kg/m³ and v=2 m/s gives NPSHa≈20.3 m.
- Pressures are absolute at the selected suction reference point.
- Compare NPSHa against manufacturer NPSHr with an appropriate project margin.
Frequently asked questions
What does this NPSH Available Calculator solve?
Calculate pump net positive suction head available from absolute suction pressure, vapor pressure, density and suction velocity.
Which units should I use?
Use the SI units shown beside each input. The results also expose practical converted outputs where useful.
Can I use this for final equipment selection?
Use it for transparent engineering estimates and cross-checks. Confirm fluid properties, manufacturer curves and applicable design codes before final selection.