Pump Power Calculator, Formula, Example, Calculation

Pump Power calculator:

Enter the flow, fluid density (available at the bottom), gravity, head and pump efficiency. Then press the calculate button to get the pump power, motor power. Also, you can change the power unit from kW to HP.

By default, we have included the 10m head water pump for the flow of 50 tons per hour. you can get the kW by pressing the calculate button.

Note: 1 m^3/hr = 1 ton.

Pump Power calculation Formula:

Pump power P_(kW) in kilowatts is equal to the product of the rate of flow q_(m³_/hr) in cubic meter per hour, fluid density ρ_(kg/m³₎ in kilogram per cubic meter, gravity g in m²/s, pump differential h_(m) head in meter and the differential pressure p_(Pa) in Pascal or N/m² divided by 36,00,000.

Hence the pump power calculation formula can be written as below,

Pump Power P_(kW) = q_(m³_/hr) x ρ_(kg/m³₎ x g_(m²_/s) x h_(m) x p_(Pa) / 3600000.

The same way pump power in horsepower formula can be written as,

Pump Power P_(HP) = q_(m³_/hr) x ρ_(kg/m³₎ x g_(m²_/s) x h_(m) x p_(Pa) / 2685600.

Also above pump power is required to lift the liquid to head meters. But for calculating the net suitable motor, you need to calculate the shaft power of the pump.

The shaft power is equal to the pump required power divided by the efficiency.

P_{(kW -Shaft)} = P_(kW) / η

Hence the required motor power in kW formula can be written as,

P_{(kW -motor)} = q_(m³_/hr) x ρ_(kg/m³₎ x g_(m²_/s) x h_(m) x p_(Pa) / (3600000 x η)

Pump power calculation example:

Let we taken a 10-meter height pump needs to lift the water @ 50 m³/hr and the pump efficiency is 67%.

Water density is 1000 kg/m³

Hence the pump required power,

P_(kW) = 50 x 1000 x 9.81 x 10 / 3600000

=1.3kW

Required motor power will be

P_(kW-motor) = 1.3 / 0.67

= 2.02 kW

Converting it into HP

= 2.02/0/0.746 = 2.7 HP.

Approximately 2.2kW, but we have a standard design of 2.2kW or 3 HP motor can be used for lifting 50 m³/hr water @ 10-meter head.

Fluid density Chart: