Pressure, area and swept volume
Theoretical static extension force = powered cylinder-port gauge pressure in bar × 100,000 × bore area in m². For double-acting retraction, subtract the rod area. This assumes negligible exhaust backpressure: the port pressure difference times effective area is an ideal static force, before friction, spring resistance or dynamic losses. No universal force margin is added.
For bore and rod in mm, A = π × bore² ÷ 4 and R = π × rod² ÷ 4. Double-acting swept litres per complete cycle = (2A − R) × stroke in mm ÷ 1,000,000. A single-acting spring-return cylinder uses A × stroke ÷ 1,000,000; extension is the powered stroke and its return stroke is not air powered.
Cycle-average consumption is not peak flow
Cycle-average free air at the entered reference pressure in L/min = swept litres per cycle × full out-and-back cycles/min × (gauge pressure + reference pressure) ÷ reference pressure. Here reference pressure also represents local atmosphere, and both air temperatures are assumed equal. The rod-area correction refines the manufacturer’s cylinder-only example, which neglects rod displacement.
This is an ideal cylinder-only air balance, not a universal ANR or ISO 1217 rating. It excludes tubing, dead volume, leaks and valve losses. The average across a complete cycle can be far below the flow needed during a fast stroke. Use the manufacturer’s instantaneous requirements when sizing valves, hoses or a peak air supply.
Worked example: a double-acting cylinder
With a 50 mm bore, 20 mm rod, 100 mm stroke, 6 bar gauge at the powered port, 10 complete cycles/min and a deliberately selected 1 bar absolute reference/atmosphere, theoretical static extension is 1,178.097245 N and retraction is 989.601686 N. Swept volume is 0.361283155 L/cycle; cycle-average reference air is 25.289820861 L/min.
For single-acting spring return at the same dimensions and reference conditions, average air use is 13.744467859 L/min. The extension force above excludes the resisting spring force. These worked figures use 1 bar absolute; the default calculator uses 1.01325, so its consumption differs slightly.
Bring the operating sequence to the enquiry
Record simultaneous cylinders, stroke timing, required pressure and any other connected loads. The air demand planner needs consumption while equipment is running; do not pass a cycle average into it as an instantaneous peak. Include the equipment manufacturer’s flow requirement when available.