GPM to PSI Converter
Flow alone has no pressure. But a pump with a known horsepower and flow can only make so many psi.
Quick answer: Multiply the horsepower by 1,714, then divide by the flow in gpm. The answer is the pressure in psi. For example, 10 gpm, 5 hp is 857 psi, 5 gpm, 3 hp is 1,028.4 psi and 25 gpm, 10 hp is 685.6 psi.
The gpm to psi formula
Hydraulic horsepower is the flow in gpm times the pressure in psi, divided by 1,714 (Engineers Edge: Hydraulic Pump Horsepower Equation).
Turn that around and the pressure is the horsepower times 1,714, divided by the flow.
Take 10 gpm, 5 hp. 5 × 1714 ÷ 10 gives 857 psi.
Take 5 gpm, 3 hp. 3 × 1714 ÷ 5 gives 1,028.4 psi.
Flow and power to pressure
A pump turns power into flow and pressure.
For a set power, more flow means less pressure.
The 1,714 number joins gpm, psi and horsepower.
How to convert gpm to psi step by step
- Write down the flow in gpm.
- Write down the pump power in horsepower.
- Multiply the horsepower by 1,714, then divide by the gpm.
- The answer is the pressure in psi.
Example 1: 10 gpm, 5 hp
- Start with 10 gpm, 5 hp.
- 5 × 1714 ÷ 10 = 857.
- The pressure is 857 psi.
10 gpm, 5 hp = 857 psi
Example 2: 5 gpm, 3 hp
- Start with 5 gpm, 3 hp.
- 3 × 1714 ÷ 5 = 1,028.4.
- The pressure is 1,028.4 psi.
5 gpm, 3 hp = 1,028.4 psi
Example 3: 25 gpm, 10 hp
- Start with 25 gpm, 10 hp.
- 10 × 1714 ÷ 25 = 685.6.
- The pressure is 685.6 psi.
25 gpm, 10 hp = 685.6 psi
The sum treats the pump as perfect. Real pumps lose some power, so the true pressure is a little lower.
gpm to psi conversion table
| Flow and power | Pressure (psi) | Pressure (bar) |
|---|---|---|
| 5 gpm, 1 hp | 342.8 psi | 23.635 bar |
| 5 gpm, 3 hp | 1,028.4 psi | 70.906 bar |
| 10 gpm, 2 hp | 342.8 psi | 23.635 bar |
| 10 gpm, 5 hp | 857 psi | 59.088 bar |
| 15 gpm, 5 hp | 571.33 psi | 39.392 bar |
| 20 gpm, 10 hp | 857 psi | 59.088 bar |
| 25 gpm, 10 hp | 685.6 psi | 47.27 bar |
| 40 gpm, 15 hp | 642.75 psi | 44.316 bar |
The highlighted row is the default of the calculator. The last column gives bar.
A quick mental shortcut for gpm to psi
Multiply the horsepower by 1,700, then divide by the gpm. So 5 hp at 10 gpm is about 850 psi.
The exact answer is 857 psi.
What gpm measures
A gpm is one US gallon of flow each minute.
Pump and hydraulic sheets use it.
What psi measures
A psi is one pound-force pressing on one square inch (Wikipedia: Pound per square inch).
US tyre gauges, tanks and hoses use it.
A small pump
A pump with 5 hp at 10 gpm can reach about 857 psi.
That is 59.09 bar.
A low flow case
A pump with 3 hp at 5 gpm can reach about 1,028 psi.
That is 70.9 bar.
A bigger pump
A pump with 10 hp at 25 gpm can reach about 685.6 psi.
That is 47.27 bar.
Losses are ignored
The sum treats the pump as perfect. Real pumps lose some power as heat and friction.
So the real pressure is a little less than the answer.
Why 1,714
Hydraulic horsepower is gpm × psi ÷ 1,714 (Engineers Edge: Hydraulic Pump Horsepower Equation).
Solve for psi and you get hp × 1,714 ÷ gpm.
Going the other way
To go back, multiply the gpm by the psi, then divide by 1,714. The answer is the horsepower.
So 857 psi at 10 gpm is 5 hp.
Check your answer
Your psi should fall when the flow rises, for the same power.
Reverse the steps and you should get your first number.
More worked values
A 5 hp pump at 50 gpm can at most make 171.4 psi. A 1 hp pump at 20 gpm can make 85.7 psi, and a 10 hp pump at 100 gpm can make 171.4 psi.
These are upper limits for a perfect pump.
Real pumps
Real pumps lose some power as heat and friction. So the pressure you measure is lower than this figure.
Use the pump curve from the maker for design work.
Quick conversion answers
| Conversion | Result |
|---|---|
| 5 gpm, 3 hp | 1,028.4 psi |
| 10 gpm, 5 hp | 857 psi |
| 15 gpm, 5 hp | 571.33 psi |
| 20 gpm, 10 hp | 857 psi |
| 25 gpm, 10 hp | 685.6 psi |
| 40 gpm, 15 hp | 642.75 psi |
Where this conversion is used
Shop staff size pumps.
Technicians check hydraulic limits.
Students solve power sums.
Common mistakes to avoid
- Mixing up gpm and gph. One gpm is 60 gph.
- Forgetting losses. The sum is for an ideal pump. Real pumps give a little less.
- Using the wrong power. Use the power at the pump shaft, not the motor label.
- Rounding too early. The answer for 5 gpm, 3 hp is 1,028.4 psi. Cut it to 1,000 psi and you are off by about 2.8 percent, and the gap grows if you reuse it.
Related converters
A light duty pump
A pump with 1 hp at 5 gpm can reach about 342.8 psi.
That is 23.63 bar.
A big hydraulic unit
A pump with 15 hp at 40 gpm can reach about 642.8 psi.
That is 44.32 bar.
Frequently asked questions
How do I find psi from gpm?
You need the pump power too. Multiply the horsepower by 1,714, then divide by the gpm.
How many psi can 5 hp make at 10 gpm?
About 857 psi.
Why is the answer a limit?
Real pumps lose some power, so they give a little less.
What does 1,714 mean?
It joins gpm, psi and horsepower in one sum.
How many bar is 857 psi?
About 59.09 bar.
Does more flow mean less pressure?
Yes, for the same power.
Sources
- Engineers Edge: Hydraulic Pump Horsepower Equation (engineersedge.com)
- Wikipedia: Pound per square inch (en.wikipedia.org)
- Wikipedia: Bar (unit) (en.wikipedia.org)
