Hydraulic Cylinder Calculator
Calculate cylinder force, speed and flow demand from bore and pressure.
Please note: These are idealised textbook models using representative material data. They are for study, sizing and sanity-checking only — never for final design. Real engineering requires code-compliant analysis, verified material certificates and a qualified engineer’s sign-off.
What the Hydraulic Cylinder Calculator does
A hydraulic cylinder converts pressure into force over the area of its piston. Because the rod occupies part of that area on the return stroke, extend and retract behave differently — more force but less speed one way, the reverse the other.
Formula
Extend force = P × π D² ÷ 4Retract force = P × π (D² − d²) ÷ 4Speed = Q ÷ AreaHydraulic power = P × Q
Inputs explained
| Input | Unit | Required | Notes |
|---|---|---|---|
| Bore diameter | number | Yes | — |
| Bore diameter unit | one of 9 options | Yes | — |
| Rod diameter | number | Yes | — |
| Rod diameter unit | one of 9 options | Yes | — |
| Operating pressure | number | Yes | — |
| Operating pressure unit | one of 7 options | Yes | — |
| Pump flow rate | L/min | Optional | Accepts 0 or more. |
| Stroke length | number | Optional | — |
| Stroke length unit | one of 9 options | Yes | — |
| Mechanical efficiency | % | Optional | — |
How to use it
- Choose Bore diameter unit and Rod diameter unit.
- Enter Bore diameter, Rod diameter and Operating pressure.
- Optionally add Pump flow rate, Stroke length and Mechanical efficiency.
- Select Calculate.
Worked example
A 63 mm bore cylinder with a 36 mm rod at 160 bar, fed by 20 L/min.
- Bore
- 63 mm
- Rod
- 36 mm
- Pressure
- 160 bar
- Flow
- 20 L/min
- Efficiency
- 95%
Bore area 3,117 mm² gives 47.4 kN extending at 95% mechanical efficiency; the 2,099 mm² annulus gives 31.9 kN retracting. At 20 L/min it extends at 107 mm/s and retracts at 159 mm/s.
Frequently asked questions
Why is retract force lower than extend force?
The rod occupies part of the piston face on the return side, so pressure acts on a smaller annular area. Same pressure, less area, less force.
Why does it retract faster?
The same reason in reverse — the smaller annular volume fills more quickly at a given flow rate.
Method and sources
Method. Force as pressure times effective area — full bore area on extension, bore less rod area on retraction — with speed from flow rate over area.
Assumptions
- The pressure entered is available at the cylinder, and friction and leakage are ignored.
Limitations
- Real cylinders lose several per cent of theoretical force to seal friction, and more at low pressure or when cold.
- Retraction force is always lower than extension because the rod occupies part of the piston area — a difference that surprises people sizing for the return stroke.
- Pressure at the cylinder is below pump pressure by the losses through hoses and valves, so using the pump rating overstates force.
Sources
- The cylinder manufacturer's specification — Varies by manufacturer. Rated working pressure, effective areas and the friction allowance for a specific cylinder.