Pump Power Calculator
Find the hydraulic power delivered to a fluid, and the shaft power a pump driver needs to supply, from flow rate, total head, and pump efficiency.
Enter your values
Flow, head, fluid, and pump efficiency.
How this calculator works
Hydraulic power is the rate of useful energy transferred to the fluid — raising it through the total head at the given flow rate:
Where ρ is fluid density in kg/m³, g is 9.81 m/s², Q is flow rate in m³/s (converted automatically from your m³/h entry), and H is total head in meters. Since real pumps have internal losses, the driver must supply more than the hydraulic power:
η is pump efficiency as a decimal (the calculator converts your % entry automatically). Shaft power is the figure to use when sizing a motor.
Typical centrifugal pump efficiencies
| Pump size / type | Typical efficiency |
|---|---|
| Small centrifugal (<10 kW) | 40 – 60% |
| Medium centrifugal (10–100 kW) | 60 – 80% |
| Large centrifugal (>100 kW) | 75 – 90% |
These are general reference ranges — always use the pump manufacturer's performance curve where available.
Frequently asked questions
What head value should I use?
Use total dynamic head — the sum of static lift, friction losses in the pipe run, and any pressure the discharge point requires — not just the static height difference.
Should I add a safety margin when selecting a motor?
Yes — motors are commonly sized with 10–20% margin above calculated shaft power to cover starting torque, performance curve variation, and future duty changes.