How much push and pull force does a Ø50 mm cylinder with a Ø20 mm rod deliver at 6 bar?
Work with the pressure difference
The base force is F = p · A. On extend, the pressure acts on the full piston area. On retract, the rod takes up part of that area. Convert bar to N/mm²: 1 bar = 0.1 N/mm². The calculator uses gauge pressure and assumes atmospheric pressure on the vented side.
Worked example Ø50 / Ø20
The full area is π · 50² / 4 = 1,963.50 mm². The annular area is π · (50² − 20²) / 4 = 1,649.34 mm². At 6 bar, the theoretical forces are 1,178.10 N extending and 989.60 N retracting. With an assumed force factor of 90%, these become 1,060.29 N and 890.64 N.
Force isn't cylinder selection yet
Use the pressure at the cylinder during motion, not just the set supply pressure. Piping, valves and back-pressure affect the operating point. The force factor is a simplified deduction for losses, not a universal manufacturer value. A long rod also needs a buckling check; side loads often call for a separate guide.
Assumptions and applicability limits
The model calculates static axial force. Speed, air consumption, cushioning, buckling, acceleration and stopping behaviour are not included. For a vertical load, the weight and the required behaviour on pressure loss must also be assessed separately.
Further reading: Festo — Cylinder sizing by piston force ↗