SCFM stands for Standard Cubic Feet per Minute, which is the flow rate of a gas or air through a compressor at standard temperature and pressure conditions. The standard temperature for calculating SCFM flow rate ranges from 60°F to 68°F, at a pressure of 14.7 psi and relative humidity of 36% . SCFM measures volumetric airflow at standard conditions, so it will always be higher than the CFM value for an air compressor. CFM, or Cubic Feet per Minute, measures the volume of air that the air compressor delivers to pneumatic tools, and the temperature and pressure components are variable. Essentially, volumetric flow rate in CFM indicates the air flow rate measured for actual conditions, i.e. actual temperature, and actual pressure. However, air density will change with temperature and pressure, which is where a more scientific calculation, such as SCFM comes in handy. The CFM rating of an air compressor will always be lower than its SCFM rating because most manufacturers measure the CFM at a point where the air pressure is lower or equal to 90 PSI. For an appropriate comparison between different compressors, it is better to use SCFM rating instead of the CFM rating because in SCFM, all the measurements are calculated back to a set of standard conditions.