Cylinder Sizing & Force

Bore Dia. & Cylinder Area
Bore Dia:	Cylinder Area (Sq. in.)
7/16"	0.150
9/16"	0.249
3/4"	0.442
7/8"	0.601
1-1/16"	0.887
1-1/4"	1.23
1-1/2"	1.77
2"	3.14
2-1/2"	4.91
3"	7.07
3-1/4"	8.30
4"	12.57
5"	19.64
6"	28.27
8"	50.27
10"	78.54
12"	113.10

Cylinder Sizing

The equations below & chart at right show the relationship between the force required to move a load, the pressure available and the required cylinder bore size. Always factor in 25% more force than actually required to overcome friction, pressure drop, and other factors.

Given:

Pressure (PSI) = Force(lbs) ÷ Area(sq-in)
Piston Area = π × r²
Cylinder Bore (in) = 2 × r

Therefore:

P = F ÷ (π × (B ÷ 2)²)

And solving for B:

Where:

F = Force Required, the estimated force needed to move the load (lbs)
P = Air Pressure, the nominal air pressure of the pneumatic system (PSI)

Interactive Cylinder Bore Calculator:

Minimum Bore Required (inches) =	Bore	=
				4 ×	Enter Force Required (lbs) (include 25% cushion)
				π × 10 PSI 20 PSI 30 PSI 40 PSI 50 PSI 60 PSI 70 PSI 80 PSI 90 PSI 100 PSI 110 PSI 120 PSI	Select System Pressure

Next largest NITRA cylinder available: Next largest NITRA metric cylinder:

Cylinder Force

The force a cylinder can apply during extension is a simple calculation (the inverse of the above formula): the effective surface area of the cylinder's piston × the differential pressure. For example: a 4" cylinder has a surface area of 12.57 square in. (πr²). If that cylinder is extended with 100 PSI of air pressure, it can supply a force of 1257 pounds.

Factoring in the Rod

When retracting a double acting cylinder, the cylinder rod blocks a portion of the effective surface area. If that same 4" cylinder has a 1" rod, the effective surface area is reduced to 11.78 sq. in. and it can only supply 1178 pounds of force while retracting (given the same 100 PSI differential pressure).The following chart shows the available force (in pounds) for both extension and retraction. White rows show extension force, which takes advantage of the full piston area. Grey rows show retraction forces with the rod diameter taken into account.

Spring Return

If you choose a cylinder with spring return, be sure to factor in the additional force needed to overcome the spring during extension.

Differential Pressure

Pressures shown across the top of the chart are differential pressures across the two cylinder ports. In practice, the air supply line must supply another 5% of pressure to make up for cylinder loss, and must supply 25-50% additional pressure to make up for flow losses in lines and valving so the cylinder will have sufficient travel speed.

Systems should always be designed with calculated forces at least 25% above the actual requirements.