CFM Versus PSI

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cfm psi
(Last Updated On: September 19, 2020)

CFM versus PSI ;  The flow, the pressure, is either enough for your air tool or compressed air application?

CFM is the acronym for Cubic Feet per Minute. It is a measure of flow, as in, this compressor flows 4 CFM of compressed air.

If your air tool needs 4 CFM of compressed air to run properly, and you have an air compressor that will deliver 4 CFM of compressed air flow, then you’re golden… right?

CFM versus PSI - www.understanding-air-compressor.comNope.

An air tool needs to have a certain flow of compressed air to run properly. That is the CFM part.

Yet the air tool also needs that flow of air the CFM at a certain pressure, and that’s where the PSI comes into it.

CFM Versus PSI

The pressure of compressed air, in North America, is typically measured in PSI. PSI is an acronym for Pounds per Square Inch.

How can you tell the PSI of your compressed air? The air gauge on your air compressor displays the PSI of the compressed air in the compressor tank.

If you run an air line out to an impact wrench like this beauty from Ingersoll Rand, for example, and feed it the necessary flow of air it requires, but at 10 PSI pressure, odds are very good the impact wrench won’t be able to remove the lug nut from your vehicle wheel. Odds are good that pressure may not even turn the socket, even though you are feeding the wrench with the right flow.


Ingersoll Rand 7803RAKC Reversible Air Drill
The specifications for the air tool, along with telling you how wonderful the tool it, should also indicate the minimum hose size to flow air to the tool, the flow of air required to run that air tool, and the operating pressure for the air tool.

You need to feed the air tool with an adequate flow of air (that’s the CFM) at the correct air pressure (that’s the PSI) in order for the air tool to do the work it is designed to do.

Not fulfilling the air tool requirements, CFM versus PSI, means that the air tool will not work at all, or may not work to your satisfaction.

If your air compressor cannot deliver the pressure and the flow for your air tool, you may have a too small air compressor.


Check out this 50 Piece Professional Air Tool Kit

Hello, I am Bill, the Compressed-Air-Man. I have years of experience in industrial and residential compressed air applications, air compressors and general pneumatics. I created this site to help professionals, students, and DIYers understand and properly implement and maintain compress3ed air systems.

2 COMMENTS

  1. I hope you can help me with a problem that has been perplexing me.

    How do I calculate the amount of air entering a silo in a pneumatic filling application. the cfm of the compressor (blower) is 500 CFM at 15 psi.

    When this compress air flow enters a silo at atmospheric pressure, the compressed air will expand.

    What is the amount of air/product entering the silo in cubic feet per minute? I would like to know the formula. If you have the answer or can point me in the right direction to find the answer, your help will be greatly appreciated.

    • Mike, I’ve moved your question to a more appropriate page. What you have asked is a very, very difficult puzzle to solve. I have looked for years for a simple, or even complex, formula to figure out how the output from a compressor is affected by details similar to those in your question. I have not found an answer so far. I am hoping that a visitor, seeing this, will respond with some guidance.

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