Cylinder force calculator

WORKED FIELD EXAMPLE · HYPOTHETICAL

Compare pneumatic-cylinder push and pull force

Assume gauge pressure 0.5 MPa, a 50 mm bore and a 20 mm rod.

1. Enter the conditions

Select Korea · SI and enter pressure 0.5, bore 50 and rod 20. Theoretical push is approximately 981.75 N and pull is approximately 824.67 N.

2. Interpret the result

Pull acts on the piston area remaining after subtracting the rod area. Changing only rod diameter to 25 mm leaves push unchanged and reduces pull to approximately 736.31 N.

3. Check before applying

These theoretical values exclude friction, back pressure and supply-line pressure losses. Cylinder-port pressure during motion can differ from supply pressure. Do not treat these results as permitted lifting loads or guaranteed usable forces.

Choose the right inputs

Enter the piston bore D, rod diameter d and operating gauge pressure at the cylinder. The bore is the internal piston diameter, not the outside diameter of the tube. Upstream regulator pressure can differ from pressure at the cylinder during motion.

Formula and units

Extension area A₁ = πD²/4. Retraction area A₂ = π(D² − d²)/4. With pressure in MPa and area in mm², F = P × A gives newtons. Retraction uses the annular area after subtracting the rod cross section.

1 MPa = 10 bar; 1 kgf = 9.80665 N; 1 lbf = 4.4482216152605 N; 1 in = 25.4 mm. US inputs convert using 1 psi ≈ 0.006894757293168361 MPa.

Worked example: 50 mm bore

At 0.5 MPa, a 50 mm bore and 20 mm rod give an extension area of 1,963.4954 mm² and retraction area of 1,649.3361 mm². Theoretical force is 981.7477 N (100.1103 kgf) extending and 824.6681 N (84.0926 kgf) retracting. Retraction force is 84% of extension force at equal pressure.

What changes at 0.6 MPa?

The same dimensions give 1,178.0972 N extending and 989.6017 N retracting. A 20% pressure increase produces a 20% theoretical force increase. Check the equipment pressure rating separately.

Why actual force differs

This model assumes pressure on the driving side and neglects back pressure on the opposite side. Seal friction, pressure losses, back pressure, acceleration, orientation and load affect actual force. The single-rod formula does not directly model spring-return, double-rod, telescopic or tandem cylinders.

Common questions

Does kgf tell me how many kilograms I can lift?

kgf measures force; kg measures mass. This result is not a safe lifting capacity. Load direction, motion, operating margins and mechanical strength require separate assessment.

What if the rod diameter is unknown?

Accurate retraction force requires rod diameter. Entering zero produces an idealized comparison without a rod-area deduction, not the actual pull force of a single-rod cylinder.

Can I use this for hydraulic cylinders?

The pressure-area relation also applies to hydraulics. Actual operating ratings, construction and performance remain product-specific.

Formula references

SMC — Cylinder theoretical output

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