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Cylinder Force Calculator

How hard a pneumatic cylinder pushes, and what pressure a given force would need. Force comes from bore and pressure alone — stroke does not change it.

Inputs

Bore is the inside diameter of the barrel, not the rod and not the outside. It is the only dimension that changes the force.

psi

Competition rules cap this at 100 psi. Real systems also sag below the regulator setting during a fast sequence.

Only count cylinders pushing the same way on the same mechanism.

Extending uses the full piston face. Retracting loses the area the rod occupies, so it is always the weaker direction.

lbf

Used only for the last two results: what pressure this force would take, and whether that is legal.

Results

Force per cylinder

—lbf

Force per cylinder

—N

Total force

—lbf

Total force

—N

Piston area

—mm²

Pressure for the force you need

—psi

Within the 100 psi limit?

—

Pressure needed, against the rule limit—

of the 100 psi cap

How this is calculated

A cylinder is a piston in a tube. Air pushes on the face of the piston, and pressure is force spread over an area, so the force you get back is the pressure multiplied by the area it acts on.

force = pressure × piston area

That is the whole calculation. Everything below is unit conversion and consequences.

Two things that surprise people

  • Stroke does not appear. A 75 mm cylinder pushes exactly as hard as a 25 mm one at the same pressure. Stroke buys distance, not strength. It does cost air, which is what theair budget tool is for.
  • Neither does speed. Force is set by pressure and area. How fast the rod moves depends on flow — tube diameter, fittings, the valve — and a mechanism can be strong and slow at the same time.

Why retracting is weaker

On the way out, air pushes on the whole circle of the piston. On the way back it pushes on that circle minus the area the rod takes up, because the rod is in the way. Same pressure, less area, less force.

VEX does not publish the rod diameter, so this tool cannot tell you the exact retract force. It shows a range instead, from a thin rod to a thick one, and the honest answer is somewhere inside it. If your mechanism only works at the top of that range, it does not work.

What you will actually feel

The number here is the force at the rod with the pressure you typed holding steady. Three things eat into it on a real robot:

  • Pressure sags. Fire several cylinders quickly and the reservoir drops below the regulator setting. The last actuation in a sequence is the weakest.
  • Seals have friction. A few percent, more on a cold or dirty cylinder.
  • Geometry usually costs more than either. A cylinder mounted at an angle to the thing it moves delivers only the component of its force along the useful direction, and that can be a large loss.

Save this as evidence

Collects what you entered, what came out, how it was worked out, and anything the tool flagged, with a timestamp and a version so someone else can reproduce it.

This is evidence, not a notebook entry. It deliberately does not write your problem statement, your reasoning, or your conclusion, because under RECF rules an Engineering Notebook has to be the students' own work and no tool may generate or organise its content. Take the numbers, decide what matters, and write it yourself.

Save this run, and compare

Keeps what is on screen so you can change something and see both sides of the change. Saved in this browser only, never uploaded.

Sources & assumptions

The 100 psi ceiling and the limit of 2 reservoirs are competition rules, not properties of the hardware.

Checked against VEX's own figure. VEX publishes 54 N of extend force for their 10 mm cylinder at 100 psi. Working it out from bore and pressure here gives 54.15 N, which agrees to within a third of a percent — so the formula on this page and the number on the packaging are the same claim.

The retract range is derived, not published: VEX does not give a rod diameter, so it is bounded by assuming a rod between a fifth and two fifths of the bore, which covers ordinary cylinder proportions.