AirCompDX

Cylinder air consumption

All calculators
Formula
SCF/cycle = (A_cap + A_annulus) × stroke ÷ 1728 × (P+14.7)/14.7 · SCFM = SCF/cycle × cycles/min
Total consumption
5.88scfm
0.2941 SCF per cycle × 1
Rod force at pressure
251lb extend
227 lb retract
Per-cylinder breakdown
Cap-end area
3.142 in²
Rod-end (annulus) area
2.835 in²
Extend swept volume
37.7 in³
Retract swept volume
34 in³
Volume per cycle incl. dead volume
78.9 in³
Average rod speed
8 in/s
Supply line check & cost
Line velocity 1,190 ft/min
Comfortable. Under 1,800 ft/min keeps pressure drop and noise in check.
Compressor power for this demand
1.18 kW
Annual energy cost
$565
Field notes
  • Size the cylinder for about 25% more force than the load needs — friction and seal drag eat the rest. If you need more force, going up a bore size costs far less air than raising system pressure.
  • Dropping a machine from 100 psi to 80 psi cuts its air consumption roughly 18% and usually still makes the load.
  • Dead volume matters: 6 ft of 3/8" hose on each port adds about 5 in³ per cycle, which on a fast machine can exceed the cylinder itself.
  • Single-acting cylinders use roughly half the air but give you a weaker, slower return.
  • Add up every cylinder, blow-off and air motor on a machine before you promise a customer their compressor is big enough — nameplate machine CFM is usually peak, not average.
Consumption is free air (SCFM at 14.7 psia, 68 °F). Add cushion charging, pilot air and any blow-off separately. Peak instantaneous demand during a fast stroke is much higher than the average shown here — that is what local storage next to the machine is for.

How to use this calculator

Estimate SCFM per cycle for a double-acting or single-acting cylinder, the rod force it develops, and whether the supply line is oversized or starved.

  1. Enter bore, rod diameter and stroke, and select single- or double-acting operation.
  2. Enter operating pressure and cycles per minute.
  3. Read extend and retract volumes, the free-air consumption per cycle and the total SCFM demand.
  4. Read extend and retract force to confirm the cylinder is not undersized for the load.
  5. Check the supply line velocity figure — keep it under roughly 30 ft/s to avoid pressure collapse during the stroke.

Frequently asked questions

How do I calculate cylinder air consumption?
Compute swept volume for each stroke (bore area × stroke, minus rod area on retract), multiply by the compression ratio (gauge pressure + 14.7, divided by 14.7) to get free air, then multiply by cycles per minute. Add dead volume in hoses and fittings for a real-world number.
How much force does an air cylinder produce?
Force equals pressure times effective piston area. A 2 in bore at 80 psi extends with about 251 lbf; on retract the rod area is subtracted, so a 5/8 in rod drops that to roughly 226 lbf. Derate 10–25% for seal friction and dynamic losses.
Why does my cylinder slow down under load?
Usually flow starvation rather than force. Undersized fittings, a restrictive quick-disconnect, long small-bore hose or an overly closed meter-out flow control will drop pressure during the stroke even though static gauge pressure looks fine.