Cylinder Sizing by Force and Pressure
Sizing a hydraulic cylinder starts with two figures: the force required and the working pressure available. From the relation force equals pressure times area you get the piston diameter. Miss the annular area on the rod side or the buckling risk of the rod and the cylinder quickly ends up undersized. This guide walks through the sizing step by step.
View hydraulic cylindersHow do I calculate force from pressure and area?
The push force of a hydraulic cylinder follows the core equation force = pressure x piston area. With the working pressure known, the required piston area comes from the rearranged form area = force divided by pressure, and from that the piston diameter. A working pressure of 160 bar equals about 16 N per square millimetre, so any piston area converts directly into a force.
Why is the pull force lower than the push force?
On extension the pressure acts on the full piston area; on retraction it acts only on the annular area, because the rod takes up part of the surface. The pull force is therefore lower than the push force. For a cylinder with a 63 mm piston and a 36 mm rod, the force drops from around 50 kN to about 34 kN. If you load both directions, size on the smaller annular area.
- Push force (extend): the full piston diameter counts.
- Pull force (retract): annular area equals piston area minus rod area.
- The piston-to-annulus area ratio also sets extend and retract speed.
- With a through rod, both forces and speeds are equal.
How do I protect the rod against buckling?
Under compressive load over long strokes the rod can buckle long before the material reaches its yield point. The decisive factors are rod diameter, free buckling length and how the mountings are supported. A safety reserve of 1.5 to 2 against buckling is common. As stroke or load grows, the rod diameter must increase or a guide must shorten the buckling length.
How do I choose pressure, series and port?
The working pressure is rarely free to pick; it is set by the power unit. A higher pressure allows a smaller cylinder for the same force but demands pressure-rated parts and clean filtration. Conversely a larger piston saves pressure and eases the seals. Series, mounting style and port size follow from force, stroke and the space available.
Check the available power-unit pressure and size the piston to it.
Compare cylindersFrequently asked questions
How large must the piston diameter be for a given force?
Divide the required force by the working pressure to get the piston area, then compute the diameter from it. At 160 bar, 1 cm² of piston area gives about 1.6 kN. For 50 kN you need roughly 31 cm², which matches a 63 mm piston.
Why does my cylinder pull less than it pushes?
On retraction the pressure acts only on the annular area, because the rod removes surface. The pull force is therefore inherently lower than the push force. Always size the pulling direction on the annular area.
What safety factor should I plan for?
Against rod buckling a factor of 1.5 to 2 is common. Pressure peaks and dynamic loads should have reserve as well. For long strokes the buckling calculation matters more than the plain force reserve.
Size the right hydraulic cylinder
Our hydraulics specialists check force, pressure, annular area and buckling for your application.
Force calculated right
Piston and annular area derived from your working pressure.
Buckling considered
Rod diameter sized with a safety reserve.
Matched to the unit
Cylinder tuned to the available pressure and flow.
Expert advice
Hydraulics specialists support your sizing.