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Mechanical EngineeringP0

Pump Sizing Calculator

Size a centrifugal pump by calculating required power from design flow, head, efficiency, and safety margin.

Inputs
Enter your values below

0.75 = 75% at BEP

1.1-1.25 typical

Result
Required Motor Power
—
Enter values and click Calculate
Formula
density × flow × 9.81 × head ÷ efficiency × safety ÷ 1000
Result unit: kW

Required Power = ρQgh/(η) × safety. /1000 converts W to kW for the final answer. Safety factor typically 1.1-1.25.

Introduction

Calculate the required motor power for a centrifugal pump given design flow, total head, efficiency, and a safety margin. Round up to the nearest standard motor size (5.5, 7.5, 11, 15, 18.5, 22, 30, 37, 45, 55, 75 kW).

Calculation Example

100 m³/h × 50m at 75% efficiency with 15% safety: 20.9 kW. Select a 22 kW standard motor.

Inputs: flow=100, head=50, density=1000, efficiency=0.75, safety=1.15
Result: 20.9 kW

Engineering Applications

  • •Pump motor sizing
  • •Equipment specification
  • •Capital cost estimating
  • •Procurement

Frequently Asked Questions

What safety factor should I use?

1.1-1.15 for well-defined systems with accurate pressure drop calcs; 1.2 for conservative estimates; 1.25+ for high-viscosity or uncertain conditions.

How do I select standard motor size?

IEC standard sizes: 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, 110 kW. Round up to nearest size.

Related Calculators

Pump Power CalculatorPump Head CalculatorPump Selection Guide Calculator

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Disclaimer: Calculations are for reference and educational purposes only. Always verify results independently for engineering design. See full disclaimer.