Piston Force Calculator

Calculate the force in a cylindrical piston from the pressure applied.

Extend force1.8703 kN6 bar over 31.172 cm²

Retract force1.5758 kN84.25% of the extend force — the rod takes up part of the piston face

Full bore area31.1725 cm²

Annulus area26.2637 cm²

Extend force in kilograms-force190.72 kgf

Force difference between strokes294.5243 Nwhy a double-acting cylinder is usually mounted to push rather than pull

Swept volume, extending623.45 cm³

Swept volume, retracting525.27 cm³less air or oil needed on the return

Work per extend stroke374.0694 J

Rod speed0.25 m/s

Power while extending467.5868 W

Flow rate needed46.759 litres a minute

At 4 bar1.2469 kNextend force

At 8 bar2.4938 kNextend force

At 10 bar3.1172 kNextend force

The formula

F = pA, with A = πd²/4

The rod side is weaker

Force is pressure times area, and a double-acting cylinder has two different areas. Extending, the pressure acts on the full bore. Retracting, it acts on the bore minus the rod cross-section, so the force is smaller — often by twenty or thirty percent. That asymmetry is why cylinders are normally arranged so the working stroke is the push.

It also means the return stroke needs less fluid, so a cylinder retracts faster than it extends at the same flow rate. In hydraulics with a fixed pump that produces a noticeably quicker return, which is sometimes useful and sometimes has to be throttled.

Bore enters squared, so a 25% larger bore gives a 56% larger force at the same pressure. Increasing bore is almost always cheaper and safer than raising system pressure, which is limited by seals, hoses and fittings.