Calculator
Pump Affinity Law Calculator
Predict how flow, head and power change when pump speed or impeller diameter changes — the affinity laws, essential for VSD optimisation and impeller trimming.
Interactive toolUpdated July 2026
Inputs (Baseline)
Ratio n₂/n₁ = 1.207
Results (New)
Flow
121
Head (m)
43.70
Power (kW)
3.69
Flow
100.0 → 120.7
Head
30.0 → 43.7
Power
2.1 → 3.7
How It Works
Q₂/Q₁ = n₂/n₁
H₂/H₁ = (n₂/n₁)²
P₂/P₁ = (n₂/n₁)³
Power scales with the cube of speed — a small speed reduction gives a large energy saving. The same laws apply replacing speed with impeller diameter ratio.