HP to PSI Calculator
Work out the pressure a hydraulic system can produce from its horsepower and flow rate.
Horsepower and pressure are not interchangeable. In a hydraulic system, power is what pressure and flow produce together — squeeze the same power through less flow and pressure rises; open the flow up and pressure falls. That trade-off is the whole basis of the conversion.
Why You Cannot Convert HP to PSI Alone
Asking how much PSI is in 20 horsepower is like asking how wide a room is when you only know its floor area. Without the second dimension there is no answer.
The same 20 HP produces 3,428 PSI at 10 GPM, but only 1,714 PSI at 20 GPM, and 6,856 PSI at 5 GPM. The power has not changed at all — only how it is distributed between pushing hard and moving quickly.
| Power | At 5 GPM | At 10 GPM | At 20 GPM | At 40 GPM |
|---|---|---|---|---|
| 5 HP | 1,714 | 857 | 429 | 214 |
| 10 HP | 3,428 | 1,714 | 857 | 429 |
| 20 HP | 6,856 | 3,428 | 1,714 | 857 |
| 50 HP | 17,140 | 8,570 | 4,285 | 2,143 |
All figures in PSI. Note how quickly pressures climb at low flow — a reminder that component ratings, not arithmetic, set the real ceiling on any system.
Efficiency and Real Systems
The formula gives hydraulic horsepower — the useful work done by the fluid. The motor driving the pump must supply more than that, because no pump is perfect. Typical gear pumps run around 85% efficient, piston pumps somewhat higher.
To size the driving motor, divide the hydraulic horsepower by pump efficiency. A system needing 20 hydraulic HP through an 85% efficient pump requires about 23.5 HP at the input shaft. The calculator above shows this input requirement alongside the pressure figure.
Pressure Is Limited by Hardware, Not Maths
The formula will happily tell you that 50 HP at 2 GPM gives 42,850 PSI. No standard hydraulic system will do that. Real limits come from component ratings: most mobile equipment runs 2,000–3,000 PSI, industrial systems 3,000–5,000 PSI, and high-pressure specialist equipment up to around 10,000 PSI.
If your calculation returns a pressure above the rating of your pump, hoses or cylinders, the relief valve will open and the surplus power will turn into heat rather than pressure. That is a design problem, not a calculation problem.
Related Hydraulic Conversions
For the reverse calculation, our PSI to HP calculator works out power from pressure and flow. To size a pump for a given duty, use the hydraulic horsepower calculator, and for water pumping specifically see pump horsepower. If you are sizing the electric motor to drive the pump, the electric motor HP calculator handles the electrical side.
Frequently Asked Questions
Multiply HP by 1714 and divide by flow in GPM. So 20 HP at 10 GPM = 20 × 1714 ÷ 10 = 3,428 PSI.
No. Hydraulic power is pressure × flow, so pressure cannot be recovered without flow. The same 20 HP gives 3,428 PSI at 10 GPM but only 1,714 PSI at 20 GPM.
It converts between horsepower, psi and US gallons per minute, derived from one horsepower being 33,000 ft-lbf per minute adjusted for hydraulic units.
It depends on flow. At 1 GPM, 1 HP gives 1,714 PSI; at 10 GPM it gives 171 PSI.
It affects the motor size, not the pressure. The formula gives hydraulic HP; divide by pump efficiency (around 85% for gear pumps) to find required input power.
Mobile equipment typically runs 2,000–3,000 PSI, industrial systems 3,000–5,000 PSI, and specialist equipment up to around 10,000 PSI.
Usually the relief valve opening. If calculated pressure exceeds the system setting, surplus power becomes heat instead of pressure. Internal leakage and pump wear do the same.