Pneumatic System Calculator

One estimate is the field rule of thumb of roughly 4 CFM delivered per horsepower at 90 psi, and the other is a more rigorous compression-work calculation based on the actual pressure ratio and an assumed 85% mechanical efficiency. Taking the larger of the two protects against undersizing the compressor when the simple rule of thumb breaks down, such as at unusually high or low operating pressures.

Sizing exactly to calculated demand leaves no margin for future tool additions or moments when duty cycles overlap higher than assumed, so the calculator builds in a 25% margin as typical practice when reporting the compressor CFM rating. That margin also feeds into how quickly the tank can recharge, since a compressor sized right at demand would never build back reserve pressure.

It's a ratio comparing total air demand against per-tool consumption adjusted for duty cycle, giving a rough sense of how tight your air supply is relative to how hard your tools are drawing on it — not a literal count of actuator cycles per minute for any specific cylinder. Don't treat it as a cycle-time spec for a particular pneumatic actuator; it's only a system-level tightness indicator.

The calculation only accounts for tool consumption, duty cycle, and a sizing margin — it doesn't model leaks at fittings and hose connections, pressure drop through long hose runs, or restriction from undersized piping, all of which add real demand on top of what's calculated. A shop's actual leak load alone can be a meaningful fraction of total compressor output, so build in extra margin beyond this estimate for an aging or leak-prone system.