Formula
Actual CFM = (Tank gal × ΔPSI × 0.536) / Time secHow to run the test:
- Close service valve so no air leaves the tank.
- Drain tank to start pressure (or note current).
- Start compressor, time how long to reach end pressure.
- Enter values below.
Target spec (optional)
Actual delivered flow
42.9cfm
20.24 L/s · 72.9 m³/h · ΔP 40.0 psi
What the result tells you
- Way below nameplate: worn rings, leaking reed/discharge valves, failed check valve, clogged intake filter.
- Builds fine but runs constantly: system leak downstream, or demand exceeds supply.
- Short-cycles (< 1 min load/unload): leaks, tank too small, or pressure band set too narrow.
Constant 0.536 comes from converting tank volume × pressure rise to free air (1 ft³ at 14.7 psia per 7.48 gal × 60 s/min ÷ 14.7 psi).