Hydraulic Cylinder Calculator
Enter bore, rod diameter and system pressure to get extend and retract forces — the rod side is weaker, and this shows exactly by how much.
Open calculatorLast updated: 2026-09-15
How the calculation works
- Force is pressure times area. Extending uses the full bore area; retracting uses the annulus (bore minus rod).
- The retract figure shows the force penalty of the rod — typically 30–50% less than extend at the same pressure.
Worked example
Interpreting the result
The extend/retract asymmetry is a design lever: rodless cylinders push and pull equally; big rods trade retract force for buckling stiffness. Real output is 5–10% below calculated (seals, line losses), and long strokes in compression need rod buckling checks before force checks.
Assumptions
- Standard double-acting cylinder with round rod.
- Neglects seal friction and back-pressure on the exhaust side.
Limitations
- Regenerative circuits (rod and cap sides connected) behave differently.
- Telescopic and plunger cylinders have distinct areas.
Push force (kN) by bore and pressure
| Bore | 100 bar | 160 bar | 210 bar |
|---|---|---|---|
| 40 mm | 12.6 | 20.1 | 26.4 |
| 50 mm | 19.6 | 31.4 | 41.2 |
| 63 mm | 31.2 | 49.9 | 65.5 |
| 80 mm | 50.3 | 80.4 | 105.6 |
| 100 mm | 78.5 | 125.7 | 164.9 |
Force = pressure × piston area. Real force is lower by seal friction and by any pressure lost between pump and cylinder.
Retract force of a 63 mm bore cylinder at 160 bar by rod diameter
| Rod diameter | Retract force (kN) | Share of push force |
|---|---|---|
| 28 mm | 40.0 | 80 % |
| 36 mm | 33.6 | 67 % |
| 45 mm | 24.4 | 49 % |
Worked scenario: a 63 / 28 mm cylinder at 160 bar
The push force is 49.9 kN (11,213 lbf). On the return stroke the rod takes up part of the piston area, so the retract force is 40.0 kN. A thicker rod gives a stronger rod but a weaker pull.
Mistakes to avoid
- Mixing pressure units. 1 bar is 14.5 psi, and a wrong unit changes the force by that factor.
- Using the pump's pressure rating instead of the pressure that actually reaches the cylinder.
- Forgetting that a long, slender rod under compression also has to be checked against buckling.
Frequently asked questions
How much force does a 4-inch cylinder make at 2000 psi?
F = 2000 × π × 2² = 25,133 lbf ≈ 12.5 tons extending. Retracting with a 2-inch rod: 18,850 lbf.
Why is retract force lower?
The rod occupies area on the retract side, so the same pressure acts on less piston area — the annulus.