Pneumatic cylinder force calculator with load factor and air consumption
This pneumatic cylinder force calculator works like the SMC selection guide: theoretical force = pressure × piston area, pulling on the smaller ring area. Because friction and acceleration eat part of it, only a share of that force may be used as load – the load factor. A 50 mm bore with a 20 mm rod at 5 bar (0.5 MPa) gives 981.7 N extending and 824.7 N retracting.
Example: Bore (piston diameter) 50 mm · Rod diameter 20 mm · Pressure unit: bar · Operating pressure 5 · Type of operation: dynamic – moving a load (η 0.5) · Stroke (optional) 100 mm · Cycles per minute (optional) 10 → Theoretical force: Extend 981.7 N · retract 824.7 N. Source: SMC – Technical data for air cylinders / Air Cylinders Model Selection (catalogue pp. 1569–1576): load factor η (static ≤ 0.7, dynamic ≤ 0.5, horizontal on guide ≤ 1), regulator 85 % of source pressure, Data 2 air consumption eq. (8)–(12), Data 3 theoretical output table (read 09.10.2026). Updated: .
How it is calculated
Force = pressure × area. SMC calls this the “theoretical output”: operating pressure times the piston area, assuming no resistance in the cylinder. Retracting, the rod cross-section is missing, so the force is smaller. 1 MPa on 1 mm² is exactly 1 N, which makes the metric calculation simple.
Theoretical output at 0.5 MPa (5 bar)
| Bore / rod | Extend | Retract |
|---|---|---|
| 20 / 8 mm | 157.1 N | 131.9 N |
| 32 / 12 mm | 402.1 N | 345.6 N |
| 40 / 16 mm | 628.3 N | 527.8 N |
| 50 / 20 mm | 981.7 N | 824.7 N |
| 63 / 20 mm | 1,558.6 N | 1,401.5 N |
| 80 / 25 mm | 2,513.3 N | 2,267.8 N |
| 100 / 30 mm | 3,927.0 N | 3,573.6 N |
SMC’s own table rounds these values (e.g. 980 N and 825 N for 50/20 mm).
Load factor and bore selection
SMC limits the load to a share η of the theoretical force: up to 0.7 for static work such as clamping, up to 0.5 when a load is moved, up to 1 when the load runs horizontally on a guide – and less for high speeds. So the 50 mm cylinder at 5 bar may move about 490.9 N. Reversed, a load of 300 N needs at least a 39.1 mm bore at 0.5 MPa and η 0.5 – the next standard size is 40 mm. As operating pressure SMC generally sets the regulator to 85 % of the supply pressure.
Air consumption
Per stroke the cylinder fills its volume at operating pressure, counted as free air: area × stroke × (P + 0.1) ÷ 0.1. For 50/20 mm, 100 mm stroke and 0.5 MPa that is 2.168 dm³ (ANR) per cycle, at 10 cycles per minute 21.68 l/min. Convert pressures with bar to psi; for oil instead of air use the hydraulic cylinder calculator, and for the basics the force calculator.
Frequently asked questions
How do you calculate the force of a pneumatic cylinder?
Pressure in MPa times piston area in mm² gives newtons. 50 mm bore = 1,963.5 mm²; at 0.5 MPa that is 981.7 N.
Why is the retract force lower?
The rod covers part of the piston. With a 20 mm rod the ring area is 1,649.3 mm², so the force at 0.5 MPa is 824.7 N.
What load factor should I use?
SMC: 0.7 or less for static operation (clamping), 0.5 or less for moving a load, up to 1 for horizontal movement on a guide, lower still for high speed.
What bore do I need for a 300 N load?
At 0.5 MPa and load factor 0.5: √(4 × 300 ÷ (π × 0.5 × 0.5)) = 39.1 mm, so a 40 mm cylinder.
How much air does a cylinder use?
Area × stroke × (P + 0.1) ÷ 0.1 per stroke. 50/20 mm, 100 mm stroke, 0.5 MPa: 2.168 dm³ (ANR) per cycle.
What does 5 bar give in pounds?
The 50 mm cylinder pushes 981.7 N, which is 220.7 lbf (1 lbf = 4.448 N).
Sources and legal basis
- SMC – Technical data for air cylinders / Air Cylinders Model Selection (catalogue pp. 1569–1576): load factor η (static ≤ 0.7, dynamic ≤ 0.5, horizontal on guide ≤ 1), regulator 85 % of source pressure, Data 2 air consumption eq. (8)–(12), Data 3 theoretical output table (read 09.10.2026)
- NIST SP 811, Appendix B.8 – conversion factors: 1 psi = 6 894.757 Pa, 1 lbf = 4.448 222 N (read 09.10.2026)
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