Hydraulic Cylinder Selector Calculator

Formula

• A_required = (F × SF) / P
• D_bore = √(4A / π)
• Standard bore = next ISO size ≥ calculated bore

About this calculator

Part of our Fluid Power Calculators collection. Pneumatic and hydraulic cylinder forces and system sizing.

How it works

Required piston area comes from force equals pressure times area, with a safety factor applied. The tool converts area to bore diameter and estimates retract force from your rod-to-bore ratio. Pick the next standard bore size up from the result.

Enter your values in the inputs above and click CALCULATE. Results appear on the right without a page reload. No login and no server upload.

Worked example

140 bar, 30 kN required extend force, safety factor 1.2, rod ratio 0.55.

1. Design force = 30 × 1.2 = 36 kN = 36,000 N
2. Required area = 36,000 / (140 × 10⁵) = 25.71 cm²
3. Calculated bore = √(4 × 0.002571 / π) × 1000 = 57.2 mm
4. Next standard bore = 63 mm → extend force ≈ 43.6 kN at 140 bar

Result: Size up to 63 mm bore; suggested rod ≈ 34.7 mm; retract ≈ 30.4 kN.

When to use

• First-pass hydraulic cylinder bore selection
• Checking if existing system pressure can deliver required force
• Estimating retract force after picking a standard bore

Limitations

• Standard bores are metric ISO-style sizes; manufacturer catalogs may differ slightly
• Does not select stroke, mount, or seal type
• Safety factor is user-defined; follow application standards for lifts and presses

FAQ

What safety factor should I use?

Many industrial applications use 1.25 to 2.0 depending on shock load and duty. Critical lifting applications need code-compliant factors beyond this calculator.

What is rod ratio?

Rod diameter divided by bore diameter. Enter 0.55 for a typical 63 mm bore with 35 mm rod. Higher ratio increases retract area loss.

Why round up to a standard bore?

Cylinders are sold in standard bore sizes. Rounding up ensures the selected bore meets or exceeds the calculated requirement.