How To Calculate CFM Of Air Compressor?

Air compressors can be used in a variety of different types of tools needing compressed air to work. However, it is essential to know the right amount of air pressure for each tool and for that, you must know how to calculate the CFM of air compressor.

How To Calculate CFM Of Air Compressor

CFM is the unit of air pressure measurement which is quite critical to follow as it is drastically variable. Not only that you should be aware of different other air compressing units as it’ll help in making the right decision when it comes to accurate weighing and measurements.

It is important to invest in such information if you want to work professionally or frequently with an air compressor. In this blog, we’ll be discussing an easy way of calculating CFM.

Are CFM and SCFM Same?

Before getting any deeper with the CFM, we must know the difference between CFM and SCFM as most people think of both as the same units. Although both of them are used for their equivalent tasks, they can’t be referred to as the same because when calculated, they use different standard values.

CFM is the cubic feet per minute for airflow and the standard pressure for CFM is 90 PSI, but when you want to calculate SCFM then you should work with the standard pressure and temperature defined above. Learn more about SCFM in detail.

Calculating CFM of Air Compressors

If you’re good at mathematics and mechanics of an air compressor, then measuring the CFM won’t be such a big deal. Here are some easy-to-follow steps to calculate CFM:

Measure the Tank Volume

Start the process by measuring the volume of your air compressor i.e the amount of the gallons of air that can be filled in the tank of your company. You can easily find the number on the manual of your air compressor and sometimes, it is also marked on it by the manufacturer.

Convert in Cubic Feet

Once you’ve got the tank volume then divide it by 7.48 which is the volume of the tank in one cubic foot. After calculating, you’ll get the tank volume measured in cubic feet.

Calculating CFM of Air Compressors

Release the Air

After accurately calculating the tank volume, you have to completely drain out the tank so that no air would be left. Usually, compressors beep when the compressed air has reached the minimum. You’ll find all the air released in just a short span.

For instance, if you want 125 to 135 PSI to be filled in the tank then you’ll have to wait only for 5 minutes.

Refill the Compressor

Once all the air is passed out then you can start up the air compressor to fill the new air in.

Keep an eye on your watch and note the time when you turn on. You can have room for error, but it shouldn’t exceed longer so you should be nearby or else your tank is going to blow up.

If your tank is 6 ounces then you’ll be required to wait no longer than 12 and a half minutes as overfilling can cause serious damage to you and your environment. Here is the detail guide on how to increase CFM in an air compressor.

Refill the Compressor


Note the PSIG mentioned on the tank gauge of the compressor exactly when the compressor kicks in. Later, when the compressor kicks out, you have to note the PSIG at that time as well and subtract it.

Calculate Additional Pressure

Now, you can easily divide the difference between the two recorded PSIGs by 14.7. You’ll get the additional pressure you’ve gotten when you fill the tank based on atmospheric changes. Finally, you can just multiply the tank volume in cubic feet with this number to get CFM. 


As we have reached the end of the blog, you might be having some queries. Some of them are answered as follows:

Why do you need to calculate CFM?

Calculating CFM in an air compressor is required as per the applications you’re trying to execute. Some tasks like refilling tires or backfilling the tampers doesn’t require extra CFM but rock drilling or air knives need high CFM for efficient performance.

Does an air compressor with increased CFM provide efficient performance?

As CFM means the amount of air release per minute, thus if your air compressor release a heavy amount of air then it can surely deliver efficient performance.

What should we choose CFM & SCFM?

Technically, CFM and SCFM have quite the same purpose and both are just modified versions of one another. So, if you’re aware of the mechanics and functionality both of them are offering then you can choose whichever you want. But, if you are new in this field then choosing SCFM would be safe.


Different types of tools need different pressure ratios to run it efficiently. Some need high air movement while others can swiftly run on low air levels. However, if your compressor can deliver a high CFM ratio then it can release more gas. That’s why it can be used in performing heavy-duty tasks like framing nail guns, air wrenches, and more.

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