01
Why extension and retraction force differ
The piston rod reduces the area exposed to pressure on the rod side. At equal gauge pressure, a single-rod cylinder therefore produces less theoretical retract force than extension force. A double-rod cylinder can have more nearly equal effective areas, depending on its construction.
02
Theoretical force is a starting point
The pressure-area product does not include seal friction, bearing friction, exhaust backpressure, pressure loss through the valve and tubing, imperfect alignment, or acceleration. Use the minimum expected inlet pressure and an appropriate load margin before selecting the next available bore.
03
Keep units and pressure references consistent
Pressure multiplied by area gives force only when the units are compatible. For example, 1 MPa equals 1 N/mm². Cylinder force commonly uses gauge pressure because atmospheric pressure acts on both external sides, while gas-law calculations require absolute pressure.
Selection checklist
What to verify before selection
- 01
Bore and rod diameter
- 02
Extension or retraction direction
- 03
Minimum inlet gauge pressure
- 04
Exhaust backpressure
- 05
Friction and load margin
- 06
Compatible force units
Application caution
Common mistakes
- Using full bore area for retraction
- Mixing bar, MPa, inches, and millimetres without conversion
- Calling the pressure-area result guaranteed output force
FAQ