Enter the density of the fluid, flow rate, head, and power input into the calculator to determine the pump efficiency.

Pump Efficiency Formula

The following formula is used to calculate pump efficiency.

n = ( p*g*Q*H ) / P 
  • Where n is the efficiency
  • p is the density of the fluid being moved by the pump
  • g is the gravitational constant
  • Q is the flow rate
  • H is the head
  • P is the power input

This formula can further be simplified to power output divided by power input. This is the case because the power output of a pump is calculated using the numerator of the equation above.

To calculate the pump efficiency, multiply the density, gravitational constant, flow rate, and head together, then divide by the power input.

Example Problem

How to calculate pump efficiency?

To calculate pump efficiency, you first need to determine the variables presented in the equation above. The first of which is the density of the fluid. For this example, we will assume the fluid is water and has a density of 997 kg/m^3.

Next, determine the flow rate of the pump. Using either published data, or experimental data, we find the pump volumetric flow rate to be 20 m^3/s.

Next, the head is calculated to be 5m.

Next, calculate the power input. This is the power that the pump consumes for operation. For this problem, the pump consumes 50 W of power.

Finally, using all of the values above, the pump efficiency can be calculated using the equation: ( p*g*Q*H ) / P

So, (997*6.647*10^-11*11 * 20) / 50

= .000000291

= .0000291%