Pump Power Calculator

Calculate pump power requirements and efficiency for fluid transfer systems.

Enter values to calculate

Pump power result

Free download

Get the printable pipe flow chart

Schedule 40 pipe sizes, water flow in GPM and LPM at four design velocities, and recommended velocities by application. One PDF, made to pin above the bench.

We store your email with EmailOctopus to send the chart and occasional flow-rate tips, nothing else. Unsubscribe any time. Privacy policy.

How It Works

The Pump Power Calculator uses fundamental hydraulic power equations to determine the power requirements for pump systems. It calculates both hydraulic power and shaft power, accounting for pump efficiency.

Hydraulic Power Formula

The hydraulic power is calculated using:

Ph = ρ × g × Q × H

Where:

  • • Ph = Hydraulic power (W)
  • • ρ = Fluid density (kg/m³)
  • • g = Gravitational acceleration (m/s²)
  • • Q = Flow rate (m³/s)
  • • H = Total head (m)

Shaft Power and Efficiency

The shaft power required is:

Ps = Ph / η

Where:

  • • Ps = Shaft power (W)
  • • η = Pump efficiency (decimal)
  • • Power loss = Ps - Ph

Shaft power is where the hydraulic job becomes an electrical one. Once you have the figure in kW, work out what the motor will actually draw with the motor full-load amps calculator — that current is what sizes the cable and the protective device feeding the pump.

FAQ

Here you will find the answers to the frequently asked questions about pump power calculations.

Frequently Asked Questions

What is the difference between hydraulic and shaft power?

Hydraulic power is the power actually delivered to the fluid, while shaft power is the power required at the pump shaft. The difference represents losses due to mechanical inefficiencies, bearing friction, and other factors. Shaft power is always greater than hydraulic power.

How do I determine pump efficiency?

Pump efficiency varies with pump type, size, and operating conditions. Centrifugal pumps typically have 60-85% efficiency, while positive displacement pumps can reach 90-95%. Check manufacturer specifications or use typical values: 75% for general applications, 85% for well-designed systems.

What units should I use for the calculations?

The calculator supports both SI and Imperial units. For SI, use m³/s for flow rate, meters for head, kg/m³ for density, and W for power. For Imperial, use ft³/s for flow rate, feet for head, lb/ft³ for density, and hp for power. The calculator automatically converts between units.

How does fluid density affect pump power?

Power is directly proportional to fluid density. Denser fluids require more power to pump the same volume at the same head. For example, pumping oil (density ~800 kg/m³) requires about 20% less power than pumping water (density ~1000 kg/m³) under the same conditions.

What is specific speed and why is it important?

Specific speed is a dimensionless parameter that characterizes pump geometry and performance. It helps engineers select the appropriate pump type for their application. Low specific speed pumps (radial flow) are good for high head, low flow applications, while high specific speed pumps (axial flow) are better for low head, high flow applications.

Embed This Calculator

Add this free calculator to your website. Copy the code below and paste it into your page.

Related Calculators

Continue your analysis with these related engineering tools

Total Dynamic Head Calculator

Pump head from lift, pressure, friction and fittings

Head Loss Calculator

K-value method for fittings and valve head loss

Pressure Drop Calculator

Darcy-Weisbach pressure loss in piping systems

Flow Rate Calculator

Calculate pipe flow using the Hazen-Williams equation

PSI to Feet of Head

Convert pressure in psi to head in feet of liquid

Bar to Metres Head

Convert pressure in bar to metres of water column

Flow Rate Calculator

Professional hydraulic engineering calculators for engineers, technicians, and students.

Company & Resources

Related Tools

© 2026 Flow Rate Calculator. All rights reserved. A Nomogram Works site.

Privacy Policy Terms of Service Cookie Policy