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Pump Sizing

Pump Sizing Calculator

Estimate hydraulic power, motor size, and pump type for your application. Enter flow rate and total dynamic head to get an instant recommendation.

How to use this pump sizing calculator

Pump sizing starts with two numbers — how much fluid you need to move (flow rate) and how much resistance the pump must overcome (total dynamic head, the sum of static lift, friction loss, and pressure requirement). The hydraulic power formula is P = (ρ × g × Q × H) / 3,600,000, giving kilowatts when flow is in m³/h and head is in metres. Divide by pump efficiency (typically 65–80% for centrifugal pumps) to get the shaft power the motor must deliver, then add a 15–20% service margin and round up to the next standard IEC motor rating.

For heads under 150 m with water-like fluids, a single-stage centrifugal pump is the default choice. Above 150 m or for chemical metering, consider multistage centrifugal or positive displacement designs. For viscous fluids and slurries, positive displacement pumps maintain flow regardless of pressure variation.

FAQ

What is total dynamic head?

Total dynamic head (TDH) is the total equivalent pressure the pump must generate, expressed in metres of fluid column. It includes static lift (vertical rise), friction loss through pipes and fittings, and any required discharge pressure at the outlet.

What pump efficiency should I use?

Use 65–75% for small centrifugal pumps, 75–85% for larger industrial pumps at best efficiency point (BEP), and 50–65% for positive displacement pumps handling viscous fluids. Check the manufacturer curve for your specific duty point.

Why add a service margin to motor size?

Motors should run at 75–85% of nameplate for thermal safety and to handle process variation, starting surges, and fluid density changes. Rounding up to the next standard IEC size (0.75, 1.1, 1.5, 2.2, 3, 4, 5.5, 7.5, 11, 15, 18.5, 22, 30, 37, 45, 55, 75, 90 kW) is industry standard.

Which pump type is right for my application?

Centrifugal pumps suit clean water, low-viscosity fluids, and high-flow low-head duties. Multistage centrifugal handles high head with moderate flow. Positive displacement (gear, screw, diaphragm) is preferred for viscous fluids, shear-sensitive fluids, or when precise flow metering is required.