About the Pump Affinity Laws Calculator Online Free Tool

The Pump Affinity Laws Calculator Online Free Tool estimates how pump flow, head, and power change when rotational speed changes, using the standard affinity law relationships.

How to Use the Pump Affinity Laws Calculator Online

1. Enter the base flow, head, power, and base pump speed.
2. Enter the new pump speed you want to evaluate.
3. Run the calculation to estimate scaled flow, head, and power.
4. Check the result against the actual pump curve before using it for selection.

Choosing Options Correctly

Base values:
Use values from the same operating point on the same pump curve.

Speed values:
Keep N1 and N2 in the same units, normally rpm.

Common Use Cases

• Estimate pump duty changes from VFD speed changes.
• Compare power draw at a higher or lower speed.
• Screen pump operating points before checking the manufacturer curve.

Quick FAQ

What do pump affinity laws estimate?
They estimate how flow, head, and power change with pump speed or impeller diameter under similar conditions.

Do they work for every pump change?
No. They are approximations and work best for small changes in a similar operating region.

Why does power change so quickly?
Power varies roughly with the cube of speed, so small speed increases can greatly increase power demand.

Should I still check the pump curve?
Yes. Verify the new duty point, efficiency, NPSH, motor load, and operating limits on manufacturer data.