How to use this calculator
- Enter bore. Use the cylinder bore or piston diameter.
- Enter rod diameter. Use 0 for a single-acting plunger or the actual rod for retract force.
- Enter pressure. Use working gauge pressure at the cylinder, after regulator and line losses.
- Set efficiency. Use 100 percent for theoretical force, or derate for practical sizing.
- Read force. Compare extend and retract force, then size valves and structure separately.
How it works
Pneumatic force is pressure times effective area:
F = P x A
Extend force uses full piston area A_p = pi x B^2 / 4. Retract force
uses annulus area A_a = pi x (B^2 - d^2) / 4, where
B is bore and d is rod diameter.
The efficiency field multiplies the theoretical force to allow for seal friction and
practical losses. The equivalent mass is simply F/g, useful for a quick
vertical-load screen before applying proper safety factors.
Worked example
Verified against the live calculator
A 50 mm bore cylinder at 6 bar gauge has piston area
1963.5 mm^2. With 90% efficiency, extend force is
0.6 x 1963.5 x 0.90 = 1060 N.
With a 20 mm rod, retract area is 1649.3 mm^2, so
retract force is about 891 N. The same air pressure pushes harder in
extension than retraction because the rod removes area.
Frequently asked questions
How do I calculate pneumatic cylinder force?
Cylinder force is gauge pressure times effective piston area. Extend force uses the full piston area, F = P*pi*bore^2/4. Retract force subtracts the rod area: F = P*pi*(bore^2 - rod^2)/4. This calculator also applies your efficiency allowance.
Why is retract force lower than extend force?
On a double-acting cylinder, the rod occupies part of the piston area on the retract side. That annulus area is smaller than the full bore area, so retract force is lower at the same pressure.
What efficiency should I use?
Use 100 percent for theoretical force. For sizing, 85 to 95 percent is a common allowance for seal friction and losses, but the right value depends on cylinder type, pressure, speed and condition.
Is the pressure gauge or absolute?
Use gauge pressure. A typical shop air line near 6 bar gauge is 0.6 MPa, about 87 psi.
Can I use this for vertical lifting?
It gives a static equivalent mass, but real lifting requires safety factors, load guidance, side-load control, speed control, valve sizing, fail-safe behavior and applicable machine safety rules.
Does this work in imperial units?
Yes. Toggle to imperial to enter bore and rod in inches and pressure in psi. Results show force in lbf and equivalent mass in pounds.
Method & assumptions
- Pressure is gauge pressure at the cylinder port.
- Force is static; acceleration, cushion setting, flow restriction and pressure drop are not included.
- Side loads, rod buckling, mounting strength and machine safety requirements need separate checks.
- Use the valve Cv / air-consumption calculators for flow and compressor sizing.