Difference Between CFM and SCFM

There are a lot of factors one has to look out for when using the measurement units. There are two types of measurement units, one is the SI units and the other is the non-SI units.

CFM vs SCFM

The main difference between CFM and SCFM is that CFM does not have any standard pressure, volume, temperature in which the volume flow of gas is to be calculated whereas SCFM has a standard volume, pressure and temperature in which the volume flow rate of gas is measured.

Although the standards can vary from place to place, having a standardized and controlled environment to measure the rate of flow of a mass is more efficient and easy then to measure the same rate of flow of a mass in a non-standardized situation.

Many people use these terms interchangeably, but when you want to measure the rate of flow of a gas or any other mass in an industry, it is preferable to use the standard cubic feet per minute measurement instead of the CFM.

CFM stands for Cubic Feet per Minute. The term itself is very confusing as it does not have a single definition which applies to all situations.

CFM describes the volume of air that occurs at an exact pressure or temperature. In comparison to SCFM, CFM values are always a smaller number as they are calculated at a higher pressure which decreases the volume of gas and makes it smaller.

To measure CFM, the pressure is taken to under 90psi. It is more related to the internal capacity of an air compressor. There is no standard temperature or volume at which it is calculated.

SCFM stands for Standard Cubic Feet per Minute. It is the molar flow rate of a gas which is subjected to standardized conditions of fixed pressure and temperature.

There are many standard conditions for pressure, temperature and even standard relative humidity, so while choosing a standard condition care must be taken.

As the pressure is low, the volume of gas is bigger and thus SCFM is always a greater number than CFM. Although the standard values can differ from place to place, it is still preferable to use the SCFM measurement unit than the CFM.

Main Differences Between CFM and SCFM

1. CFM values are taken under the pressure of 90psi, whereas to calculate scfm, the air is expanded to a standard condition around 14.7 psia.
2. CFM is more relevant to the internal capacity of an air compressor, while SCFM is more indicative of how the gas which is pressurized to a standard value will perform at the end point applications.

For the measurement of the rate of flow of any gas, the most used technical measurement units are the CFM and SCFM.

The main difference that one needs to know about CFM and SCFM is that SCFM requires a whole controlled and standardized environment for it’s calculation whereas CFM does not have any such standard conditions for it’s calculation.

Because of this, SCFM is a more preferred measurement unit as it has a standard temperature, volume and pressure and thus, gives a precise result.

The CFM values are calculated at a pressure under 90psi whereas the SCFM values are calculated after expanding the gas to a standard value of 14.7 psi.