Work out the pressure a hydraulic pump can generate from its drive power, flow rate and efficiency.
For the electrical side of the same plant, use the main kVA to kW converter.
Every diagram and table on this page updates with the calculator above.
The fundamental relationship — hydraulic power is pressure multiplied by flow.
Rearranged for pressure. Multiply bar by 14.5038 for psi.
Power, pressure and flow are locked together. You cannot raise pressure at constant flow without supplying more input power — the physics does not permit it, whatever the catalogue implies.
A fixed motor can deliver high pressure at low flow, or high flow at low pressure, but never both. This trade-off is why hydraulic systems use variable-displacement pumps, accumulators and load-sensing controls.
| Pump type | Overall efficiency | Typical max pressure |
|---|---|---|
| External gear | 80 – 85% | 250 bar |
| Internal gear | 85 – 90% | 300 bar |
| Vane | 82 – 88% | 175 bar |
| Axial piston | 88 – 93% | 350 – 450 bar |
| Radial piston | 90 – 95% | 700 bar |
Losses appear as heat in the oil, which is why hydraulic systems need coolers and why a poorly matched pump shows up first as a rising tank temperature.
Available pressure across a range of flow rates at your drive power and efficiency.
| L/min | Pressure (bar) | Pressure (psi) |
|---|---|---|
| 5 L/min | 1,530 | 22,191 |
| 10 L/min | 765 | 11,095 |
| 15 L/min | 510 | 7,397 |
| 20 L/min | 382.5 | 5,548 |
| 30 L/min | 255 | 3,698 |
| 40 L/min | 191.3 | 2,774 |
| 50 L/min | 153 | 2,219 |
| 75 L/min | 102 | 1,479 |
| 100 L/min | 76.5 | 1,110 |
| 150 L/min | 51 | 740 |
| 200 L/min | 38.3 | 555 |
| 300 L/min | 25.5 | 370 |
Use this to check quickly whether a proposed power unit can reach the pressure a circuit needs at its required flow.
| kW | 10 L/min | 20 L/min | 30 L/min | 60 L/min | 100 L/min |
|---|---|---|---|---|---|
| 4 kW | 204 | 102 | 68 | 34 | 20 |
| 7.5 kW | 383 | 191 | 128 | 64 | 38 |
| 11 kW | 561 | 281 | 187 | 94 | 56 |
| 15 kW | 765 | 383 | 255 | 128 | 77 |
| 22 kW | 1,122 | 561 | 374 | 187 | 112 |
| 37 kW | 1,887 | 944 | 629 | 315 | 189 |
| 55 kW | 2,805 | 1,403 | 935 | 468 | 281 |
Pressure only becomes useful once it acts on an area. This is the step that turns a pump specification into the force a machine can actually exert.
Use the full bore area for extension, and bore minus rod area for retraction.
About 128 kN, or roughly 13 tonnes of push force on extension.
Retraction force is always lower, because the rod occupies part of the piston area on the annulus side.
It tells you what the pump could produce. The relief valve setting, hose ratings and cylinder ratings decide what the system is actually allowed to do.
Note: Theoretical figure. Never exceed component pressure ratings or relief valve settings.
29 calculators built on the same maths as the tool above. Each one has its own inputs, interactive diagrams and worked examples.
Common questions about converting kw to psi.