Physics

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Pump Horsepower Calculator.

Calculate hydraulic pump shaft power from flow, head, density, and efficiency.

On-device calculationNo signup
01

Set your values

Results update as you type.

Shaft power: 2,615.106667 W

Shaft power

0.000000W
Shaft power: 3.506916 hp

Shaft power

0.000000hp

Results update automatically as you type.

Use Cases

Pump Sizing for Industrial Systems

Engineers can estimate the required motor power for a pump given flow and head requirements, helping select appropriate pump and motor sizes.

Example: For a flow of 0.05 m³/s, head of 20 m, density 1000 kg/m³, and efficiency 0.75, the shaft power is about 13.1 kW.

Energy Cost Estimation

Facility managers can estimate the power consumption of pumps to calculate operating costs and compare efficiency improvements.

Example: Reducing head from 30 m to 25 m at the same flow can lower power by about 16%.

Frequently Asked Questions

How is pump shaft power calculated?
The calculator uses the formula: Power = (density × gravity × flow rate × head) / efficiency. You input fluid density (kg/m³), flow rate (m³/s), head (m), efficiency, and gravity (m/s²). The result is the hydraulic power required at the pump shaft.
What units are used in this calculator?
The calculator uses metric units: fluid density in kg/m³, flow rate in m³/s, head in meters, gravity in m/s², and efficiency as a decimal (e.g., 0.8 for 80%). The output is in watts (W).
Why is efficiency important in the calculation?
Efficiency accounts for losses in the pump. A pump with lower efficiency requires more input power to deliver the same hydraulic output. The calculator divides the ideal power by efficiency to give the actual shaft power needed.

Tips & Common Mistakes

Tips

  • Ensure flow rate is in cubic meters per second (m³/s). If you have liters per minute, convert to m³/s by dividing by 60,000.
  • Use the actual fluid density for your application. Water is about 1000 kg/m³, but other fluids like oil or slurry have different densities.
  • Enter efficiency as a decimal (e.g., 0.7 for 70%). If you know the percentage, divide by 100 first.
  • Double-check the head value: it should be the total dynamic head, including elevation and friction losses.

Common Mistakes to Avoid

  • Forgetting to convert flow rate from liters per minute to m³/s, leading to power results that are off by a factor of 60,000.
  • Using efficiency as a percentage (e.g., 70) instead of a decimal (0.7), which overestimates power by 100 times.
  • Ignoring the effect of gravity: if you change the gravity value (e.g., for other planets), the power changes accordingly.

Last updated: August 13, 2026