IES
Mechanical EngineeringP0

Pump Flow Calculator

Calculate pump flow rate from power, head, and efficiency using the hydraulic power formula.

Inputs
Enter your values below

0.75 = 75%

Result
Flow Rate
—
Enter values and click Calculate
Formula
power_input × efficiency ÷ (density × 9.81 × head) × 3600
Result unit: m³/h

Q = P_shaft × η / (ρgH). P_shaft in W (engine converts kW→W); ×3600 converts m³/s to m³/h.

Introduction

Calculate the flow rate a pump will deliver given its shaft power, efficiency, and the system head. This inverts the standard hydraulic power equation to solve for Q.

Calculation Example

15 kW pump at 75% efficiency pumping water to 40m head delivers ~103 m³/h.

Inputs: power_input=15, efficiency=0.75, head=40, density=1000
Result: 103.2 m³/h

Engineering Applications

  • •Pump performance estimation
  • •System curve analysis
  • •Flow verification
  • •Retrofit planning

Frequently Asked Questions

How accurate is this calculation?

It gives rated flow at a specific operating point. Actual flow depends on where the pump curve intersects the system curve.

Why does flow decrease as head increases?

Centrifugal pumps have a falling head-flow curve. At higher system resistance (more head), less flow can be produced for the same power.

Related Calculators

Pump Power CalculatorPump Head Calculator

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