Calculate hydraulic horsepower, flow rate, or pressure from any two values with HP/kW, GPM/L/min, and PSI/bar units.

Find fluid power; optionally estimate pump shaft input using supplied efficiency.

Use actual delivered flow and pressure difference across the pump or component. Fluid power is not shaft input or motor electrical power. This estimate alone does not size a motor or verify a hydraulic system.

Hydraulic Flow to Horsepower Formula

The following formula is used to calculate the hydraulic horsepower for a given flow rate and pressure.

HP = QUSgpm ร— Deltaโ‚šโ‚šsi / (396000 / 231)

Variables:

  • HP is the hydraulic horsepower
  • Q is the delivered flow rate in US gallons per minute (US gpm)
  • Delta_p is the pressure difference across the pump or component, in pounds per square inch (psi)

Multiply delivered US gpm by pressure difference in psi, then divide by 1714.285714โ€ฆ (396000/231). The common factor 1714 is rounded. In metric units, hydraulic kW = flow (L/min) ร— pressure difference (bar) / 600. Pump shaft input equals fluid power divided by supplied overall pump efficiency; motor electrical losses are separate.

Hydraulic Flow (GPM) to Horsepower Conversion Table (at 3000 psi pressure difference)
Flow Rate (GPM) Horsepower (HP)
0.50.875
11.750
1.52.625
23.500
35.250
47.000
58.750
7.513.125
1017.500
1221.000
1526.250
2035.000
2543.750
3052.500
3561.250
4070.000
5087.500
60105.000
75131.250
100175.000
Assumes a constant 3000 psi pressure difference and US gallons. Formula: mechanical hp = (US gpm ร— psi) / 1714.285714โ€ฆ. 1 hp โ‰ˆ 0.7457 kW; pump losses excluded.

What is Hydraulic Flow to Horsepower?

Hydraulic flow to horsepower is a measure of the power output of a hydraulic system. It is calculated based on the flow rate of the hydraulic fluid and the pressure at which it is delivered. Fluid power alone does not determine efficiency or establish safe system capability; shaft input and other losses must be measured or supplied separately. Hydraulic horsepower is commonly used in applications such as hydraulic pumps, motors, and other hydraulic equipment to ensure they are operating within their designed specifications.

How to Calculate Hydraulic Flow to Horsepower?

The following steps outline how to calculate the hydraulic horsepower.

  1. First, determine the flow rate (Q) in gallons per minute (GPM).
  2. Next, determine pressure difference across the component in psi, using actual delivered flow.
  3. Finally, calculate mechanical fluid horsepower = US gpm ร— pressure difference in psi / 1714.285714โ€ฆ.
  4. 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.

Flow rate (Q) = 10 GPM

Pressure difference = 1500 psi. Fluid power = 10 ร— 1500 / 1714.285714โ€ฆ = 8.75 hp (about 6.525 kW).