System Head Curve Calculator
Build H = H_static + k·Q² from one known duty point; outputs head at 25/50/75/125% flow.
Overlay these points on the pump curve to find where it will really run. High static fraction = poor VFD savings; high friction fraction = great ones.
Formula
System Head Curve Calculator is a free system curve for pump engineers, plumbers and plant designers — 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 System Head Curve Calculator
Build H = H_static + k·Q² from one known duty point; outputs head at 25/50/75/125% flow. The calculation implements H(Q) = H_static + k·Q², k from the known point (Karassik, Pump Handbook — system curves). Overlay these points on the pump curve to find where it will really run. High static fraction = poor VFD savings; high friction fraction = great ones.
How to use System Head Curve Calculator
- 1Enter Static head in m.
- 2Enter Known flow in m³/h.
- 3Enter Total head at that flow in m.
- 4Read Friction constant k, Head @ 25% flow, Head @ 50% flow instantly — no submit button needed.
- 5Need US units? Flip the SI/Imperial toggle and every field converts.
Why use System Head Curve Calculator?
- ✓Implements the standard formula — H(Q) = H_static + k·Q², k from the known point
- ✓Reference cited on-page: Karassik, Pump Handbook — system curves
- ✓One-click SI ⇄ Imperial toggle — values convert in place, physics stays in SI
- ✓Runs entirely in your browser — nothing uploaded, free forever
Frequently asked questions
What formula does the System Head Curve Calculator use?+
It computes H(Q) = H_static + k·Q², k from the known point, per Karassik, Pump Handbook — system curves. The formula is displayed under the result.
What should I keep in mind when using this calculator?+
Overlay these points on the pump curve to find where it will really run. High static fraction = poor VFD savings; high friction fraction = great ones.
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 System Head Curve Calculator free to use?+
Yes — 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.
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