Convert pump flow and head into hydraulic and shaft horsepower, with efficiency included.
Convert pump flow and head into hydraulic and shaft horsepower, with efficiency included.
Shaft horsepower required
How to use this tool
Pump delivery in US gallons per minute.
Total dynamic head in feet, including elevation, friction and pressure head.
1.0 for water; higher for denser liquids such as brines.
From the pump curve at the operating point; shaft power is hydraulic power divided by efficiency.
Formula & worked example
100 gpm, 50 ft head, SG 1, 75% efficiency: hydraulic power 1.2626 hp, shaft power 1.6835 hp = 1.2554 kW.
Limitations — read this before you rely on it
This uses the standard US water-horsepower formula with a single efficiency value. Real efficiency varies with flow along the pump curve, and motor efficiency, drive losses and suction conditions are separate; size motors with a safety margin above shaft power.
Frequently asked questions
The total energy the pump must add: elevation lift plus friction losses plus any pressure difference, expressed as a height of the pumped liquid.
It is the unit-conversion constant for US gallons per minute and feet of water head into horsepower.
Hydraulic power is delivered to the fluid; shaft power is what the motor must supply, higher because the pump is not 100% efficient.
Yes — pumping a denser liquid at the same flow and head needs proportionally more power.
Choose a motor rated above the shaft power at the worst expected operating point, not just the design point.