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Pump Specific Speed Calculator
Enter speed, flow and best-efficiency-point head — Nq and impeller type update instantly.
Formula
Nq = N · √Q / H0.75 (Q in m³/s, H in m) | Ns = N · √Q / H0.75 (Q in gpm, H in ft)
Impeller Classification
| Nq (metric) | Impeller type |
|---|---|
| 10 – 20 | Radial (low flow, high head) |
| 20 – 40 | Radial / Francis |
| 40 – 80 | Mixed flow |
| 80 – 160 | Axial flow (propeller) |
FAQ
What is specific speed used for?
It is a pump type classifier independent of size — given duty point you can pick the impeller family before any vendor data.
Relation between Nq and Ns?
Ns (US) = Nq × 51.65 approximately (using gpm/ft vs m³/s/m).