Hydraulic Calculator
CalculatorsWork out cylinder force, oil flow, and pump size from bore, rod, pressure, and rpm.
Not sure what to check first? Hand the result to the assistant.
About this tool
This hydraulic calculator works out the force a cylinder produces and how fast it moves, from the bore, rod, pressure, and pump flow you enter. Push (extend) force uses the full piston area, with force equal to pressure times area. Pull (retract) uses the smaller annulus area (piston minus the rod), so retract force is always lower and retract speed is higher for the same flow.
Enter the cylinder bore and rod diameters from the service manual or a quick caliper measurement, then the operating pressure of that circuit (commonly 250 to 400 bar, or about 3,600 to 5,800 PSI, on modern excavators). Add the pump flow in L/min to get cylinder speed.
Results are theoretical, before mechanical and volumetric efficiency losses. For cylinders 100 mm and larger the friction loss is usually under 2 percent, so the figures are close in practice. Always confirm critical values against your machine's manual.
Frequently asked questions
How do I find my cylinder's bore and rod size?
They are listed in the service manual or on the cylinder data tag, or you can measure them: the bore is the inside diameter of the barrel and the rod is the shiny shaft. Enter both in millimetres.
Why is pull (retract) force lower than push force?
On retract, pressure acts on the annulus area (the piston area minus the rod's cross-section), which is smaller than the full piston area. So retract force is lower and, for the same pump flow, retract speed is higher.
How do I convert bar to PSI?
Use whichever your gauge or spec sheet shows and pick the matching unit; the tool converts internally. One bar is about 14.5 PSI.
What hydraulic pressure does an excavator run at?
The operating or relief pressure of that hydraulic circuit, from the spec sheet (often 250 to 400 bar on excavators). Do not use the engine or pilot pressure.
Why are the results called theoretical?
Real output is reduced by seal friction and internal leakage. For large bores the loss is small (under about 2 percent); for very small cylinders it can be larger. Treat the numbers as a close estimate.