Gas Flow Conversions — SCFM, ACFM, CFM, m³/h

SCFM is flow at standard reference conditions (14.7 psia, 68°F, 36% RH per ANSI). ACFM is the actual volumetric flow at the system's actual pressure and temperature. SCFM = ACFM × (P_actual / P_std) × (T_std / T_actual). This means a compressor delivering 100 ACFM at 100 psig delivers about 780 SCFM.

Multiple standards exist: ANSI/CAGI uses 14.7 psia, 68°F, 36% RH. ISO uses 1 bar, 20°C, 0% RH. Always check which standard your equipment manufacturer uses — about 3% difference between ANSI and ISO standards.

Multiply CFM by 1.699 to get m³/h. For example, 100 CFM = 169.9 m³/h. The exact factor is 1.699008, derived from converting minutes to hours and cubic feet to cubic meters.

Manufacturers typically rate compressors in SCFM at the inlet, not at the discharge pressure. A 5 SCFM compressor at 90 psig inlet rating may only deliver about 0.7 CFM of compressed air at pressure. Always check the tool's consumption SCFM requirement at operating pressure, not the compressor's free-air delivery.

Nm³/h (Normal cubic meters per hour) is the metric equivalent of SCFM. It references 0°C and 1.01325 bar. 1 Nm³/h ≈ 35.31 SCFH. European and Asian manufacturers commonly use Nm³/h, while US manufacturers use SCFM/SCFH.