Enter the flow rate in gallons per minute and the total head in feet into the calculator to determine the water horsepower (WHP).

WHP Formula

The following formula is used to calculate water horsepower. 

WHP = Q*H/3960
  • Where WHP is the water horsepower (hp)
  • Q is the volumetric flow rater of the water (gpm)
  • H is the head of the water (ft)

To calculate water horsepower, multiply the water flow rate by the water head, then divide by 3960.

WHP Definition

WHP is short for water horsepower. Water horsepower is defined as the amount of work per unit of time that a pump or flow of water can generate.

Example Problem

How to calculate water horsepower?

  1. First, determine the volumetric flow rate of the water.

    For this example problem, the volumetric flow rate of the water is found to be 50 gallons per minute (GPM)

  2. Next, determine the head of the water.

    In this case, there is measured to be a total of 10 ft of head.

  3. Finally, calculate the water horsepower.

    Calculate the water horsepower using the formula above:
    WHP = Q*H/3960
    WHP = 50*10/3960
    WHP = .1262 hp

FAQ

What is the significance of the number 3960 in the water horsepower formula?

The number 3960 in the water horsepower (WHP) formula is a conversion factor used to convert the product of flow rate in gallons per minute (GPM) and head in feet to horsepower. This factor accounts for the units involved in the calculation, ensuring that the result is expressed in terms of horsepower.

How does the head of water affect the water horsepower?

The head of water, which is the height of the water column, directly affects the water horsepower. A higher head means there is more potential energy in the water flow, which can be converted into mechanical energy or work. As the head increases, so does the water horsepower, assuming the flow rate remains constant.

Can water horsepower be used to measure the efficiency of a water pump?

Yes, water horsepower can be used as a measure to evaluate the efficiency of a water pump. By comparing the water horsepower (which represents the mechanical power output) to the electrical or mechanical power input required to operate the pump, one can determine the pump’s efficiency. This efficiency is a crucial factor in selecting pumps for various applications.