Compressors and air tools - CFM vs SCFM

[California]

I've been curious about the difference between air CFM vs SCFM, ever since I bought a Harbor Freight compressor some 15 years ago, rated 5.1 CFM, that couldn't keep up with a HF die grinder rated to need 4.7 CFM.

Oh well that's just HF's marketing.

But recently looking at something from HF:

"Air Consumption 21 SCFM (3.1 CFM @ 90 PSI)"

Huh? What does all that mean?

 

[mrmikey]

Google is your friend\.
Here's the link to the complete article: What is SCFM in Air Compressors – SCFM vs. CFM Explained

What’s the Difference Between SCFM vs. CFM?​

SCFM and CFM are both essential values that indicate the airflow rate in a compressor. SCFM measures this value based on ‘ideal’ temperature and pressure conditions, while CFM measures the ‘actual’ air flow rate. CFM is the recognized value for measuring the airflow rate in the United States.

CFM (Cubic feet per minute) measures the volume of air or gas that flows through a compressor in one minute. Sometimes, the CFM rating of an air compressor a manufacturer provides may have a margin of error. Therefore, the best way to determine your air compressor’s most accurate CFM value is to test it in your facility.

 

[Roadworthy]

There is a conversion factor to get from one to the other so one may be larger or smaller than the other. SCFM Vs CFM Explained: SCFM To CFM Calculator + Chart

 

[WranglerX]

According ChatGPT

SCFM (Standard Cubic Feet per Minute) and CFM (Cubic Feet per Minute) are both units of measurement used to describe the flow rate of a gas, usually air, through a system. The main difference between them lies in the conditions under which the measurement is taken.

1. SCFM (Standard Cubic Feet per Minute): SCFM is measured at standard conditions of temperature and pressure (usually 68°F or 20°C and 14.7 psi or 1 atm). SCFM takes into account the fact that air density changes with temperature and pressure. Therefore, SCFM provides a standardized measurement that allows for comparisons between different systems regardless of the conditions in which they operate. SCFM is often used when precise calculations and comparisons are needed, such as in HVAC systems or industrial processes.
2. CFM (Cubic Feet per Minute): CFM, on the other hand, does not account for variations in temperature and pressure. It simply measures the volume of air flowing through a system in a minute without specifying any particular conditions. CFM is a more general measurement and is often used in everyday contexts where standardization is not critical, such as in household fans or portable air compressors.

In summary, while both SCFM and CFM measure airflow rate, SCFM is a standardized measurement that accounts for variations in temperature and pressure, whereas CFM is a more general measurement that does not consider such variations.