Convert GPH and pressure to hydraulic and shaft horsepower, or reverse-solve pump flow or pressure with efficiency, motor, and energy details.

Pump power balance using US gallons and pressure rise across the pump. This does not determine an actual pump operating point or a complete motor selection.

80% is an editable planning assumption; use efficiency at the operating point.

Motor and energy plan

Planning allowance only; not a motor service-factor rating.

Optional. Enter a duration to estimate electrical energy.

GPH To HP Formula

The following conventional approximation estimates required shaft horsepower from US gallons per hour, pressure rise in psi and pump efficiency. Hydraulic output horsepower omits the efficiency divisor. Pressure-based power needs no separate specific-gravity factor; only the water-head comparison assumes a water density. Actual flow and pressure require the pump and system curves.

HP = (GPH × P) / (102840 × E)

Variables:

  • HP is estimated pump shaft input horsepower; the constant 102840 = 60 × 1714 is rounded.
  • GPH is the gallons per hour
  • P is the pressure in psi
  • E is the pump efficiency (decimal)

To calculate the horsepower, multiply the gallons per hour by the pressure. Divide the result by 102,840 times the pump efficiency.

GPH to Horsepower Conversion Table (Assumes Pressure = 50 psi, Pump Efficiency = 0.70)
Flow (GPH) Shaft horsepower (HP) Shaft power (kW)
500.0350.026
1000.0690.052
1500.1040.078
2000.1390.104
2500.1740.129
3000.2080.155
4000.2780.207
5000.3470.259
6000.4170.311
7500.5210.388
9000.6250.466
10000.6950.518
12000.8330.622
15001.0420.777
18001.2500.932
20001.3891.036
25001.7361.295
30002.0841.554
35002.4311.813
40002.7782.072
*HP uses calculator formula: HP = (GPH × Pressure) / (102840 × Efficiency). Assumes Pressure = 50 psi, Efficiency = 0.70, and water (specific gravity = 1). Power in kW uses 1 hp = 0.7457 kW.

What is GPH To HP?

GPH to HP is a calculation used to determine the horsepower required to pump a certain number of gallons per hour at a specific pressure and pump efficiency. This calculation is crucial in various industries, including agriculture, manufacturing, and water treatment, where efficient pump operation is essential for optimal performance and energy savings.

How to Calculate GPH To HP?

The following steps outline how to calculate the GPH to HP.

  1. First, determine the gallons per hour (GPH).
  2. Next, determine the pressure (P) in psi.
  3. Next, determine the pump efficiency (E) as a decimal.
  4. Finally, calculate the horsepower (HP) using the formula HP = (GPH * P) / (102840 * E).
  5. After inserting the values and calculating the result, check your answer with the calculator above.

Example Problem : 

Use the following variables as an example problem to test your knowledge.

Gallons per hour (GPH) = 500

Pressure (P) = 50 psi

Pump Efficiency (E) = 0.85