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It is common to rate the compressed air consumption in Standard Cubic Feet per Minute - SCFM.
The SCFM - Standard Cubic Feet per Minute - determines the weight of air to fixed or "Standard" conditions. There are several definitions of SCFM. The most common used in the United States is with "sea-level" properties:
Europeans normally use one ata and 0oC as SCFM.

Unfortunately, real life "actual conditions" are seldom "standard conditions". When
Actual air volume flow is often termed ACFM - Actual Cubic Feet per Minute.
Actual Cubic Feet per Minute - ACFM, depends on the
of the actual air.
The conversion from SCFM to ACFM can be expressed as
ACFM = SCFM [Pstd / (Pact - Psat Φ)](Tact / Tstd) (1)
where
ACFM = Actual Cubic Feet per Minute
SCFM = Standard Cubic Feet per Minute
Pstd = Standard absolute air pressure (psia)
Pact = absolute pressure at the actual level (psia)
Psat = Saturation pressure at the actual temperature (psi)
Φ = Actual relative humidity
Tact = Actual ambient air temperature (oR)
Tstd = Standard temperature (oR)
The calculator below can used to calculate ACFM:
The actual CFM of a compressor operating at "non-standard" conditions like
can be calculated as
ACFM = 100 [14.7 (psia)/ (12.23 (psia) - 0.5069 (psia) 0.80)](540 (oR) / 520 (oR))
= 129.1
Inlet Cubic Feet per Minute - ICFM, is used by compressor vendors to establish conditions in front of additional equipment like inlet filter, blower or booster.
When air passes through the filter there will be a pressure drop. The conversion from ICFM to ACFM can be expressed as
ACFM = ICFM (Pact / Pf) (Tf / Tact) (1)
where
ICFM = Inlet Cubic Feet per Minute
Pf = Pressure after filter or inlet equipment (psia)
Tf = Temperature after filter or inlet equipment (oR)
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