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Calculators

Pump Hydraulic Horsepower

The horsepower of a pump can be determined once basic information is known about the pumping station.

Horsepower is the unit of power to define hydraulic or water horsepower. In System International System (SI) it is in kilowatts (kw).

The hydraulic power is the next energy transferred to the water per unit time. The input power delivered by the motor to the pump is called brake horsepower (bHp).

The difference between the brake horsepower and hydraulic power is the pump efficiency.


Horsepower Calculator (see formula)
Head =
 ft
Flow Rate =
 gpm
Specific Gravity =
 
HP =
 
KW =
 
Brake Horsepower Calculator (see formula)
HP =
 HP
Pump Efficiency =
 %
Brake Horsepower =
 
Brake KW =
 
SI Calculator
Pressure =
 meters
Flow Rate =
 L/S
KW =
 
HP =
 

Hydraulic Horsepower and Kilowatt Equations
Hydraulic HP = Head (ft) x Flow Rate (gpm) x (Specific Gravity)
3956
Multiply HP by 0.746 to obtain kilowatts
Hydraulic Kilowatts = (9.81) x Head (meters) x Flow Rate ( L / S ) x (Specific Gravity)
1000
Multiply kilowatts by 1.341 to obtain horsepower

 

Brake Horsepower and Motor Efficiency

Brake Horsepower = Hydraulic Power
Pump Efficiency


Once the hydraulic horsepower is known, the brake horsepower can be determined based on the pump efficiency. A pump efficiency of 60% can be used as a conservative estimate for a basic calculation to provide a general approximation.

Many technical references are available that can provide guidance on the use of these equations and the user should refer to these references.

 

Sample Horsepower Calculations

Question: Determine the estimated pump horsepower based on the 200 gpm flow rate and 100 ft discharge pressure at the pump.
HP = Head (ft) x Flow Rate (gpm) x (Specific Gravity)
3956
Pump Discharge Pressure = 100 ft
Measured Flow Rate = 200 gpm

 

Calculate Horsepower
HP = 100 ft x 200 gpm x 1.0
3956
HP = 5

 

Calculate Brake Horsepower
Brake Horsepower = 5
0.6
= 8.3

 

SI Units
Pump Discharge Pressure = 30.48 meter
Measured Flow Rate = 12.6 L / S
Kilowatts = 9.81 x 30.48 m x 12.6 L / S x 1.0
1000
Kilowatts = 3.76

 

 

Other Helpful Calculators


To print this calculator or to use it as a standalone file, please download the Excel format below. (Right-click on the link and select "Save Target As" to download it to your computer.)

Download Excel format

Legend

L/S = Liters per Second
gpm = Gallons per Minute
HP = Horsepower
KW = Kilowatt
m/s = Meters per Second
m³ = Cubic Meters
m² = Square Meters
ft² = Square Feet
ft³ = Cubic Feet

 

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Module 1: Water Use and Impacts | Module 2: Water Management Risk Assessment | Module 3: Case Examples and Links
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