Pump System Curve Calculator

A pump operates where its curve meets the system curve. Enter static head and one known duty point to build the full system curve — then read off the head your pump must beat at any flow.

Static head (ft)Elevation difference plus any constant pressure head (e.g., tank level ÷ 2.31 for psi).

Design flow (gpm)One known point on the system curve.

Total head at design flow (ft)Static head + friction and minor losses at the design flow.

System Curve

Flow (gpm)	Friction head (ft)	Total head (ft)

How the calculation works

System curve
H = H_static + K · Q²
K = (H_design − H_static) / Q_design² (ft per gpm², solved from your duty point)
Friction head at any flow = K · Q² (the square law follows from Darcy-Weisbach at constant friction factor)

Notes & limitations

The system curve is the standard pump-selection construct: static head (fixed) plus friction head (rising with the square of flow). Plot it against candidate pump curves — the intersection is the operating point. See the Hydraulic Institute standards or any pump handbook.

The square law assumes the friction factor stays roughly constant; at very low flows the curve flattens slightly.
Static head often varies (wet-well drawdown, tank levels) — build curves for the minimum and maximum static head to bracket the operating range.
Valve throttling steepens the curve (raises K); a VFD moves the pump curve instead of the system curve.
Parallel pumps share flow at a common head; series pumps add head at a common flow — each combination shifts the operating point along this curve.

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