How to Calculate Air Compressor CFM
Correctly calculating your air compressor’s CFM requirement is the first step to ensuring that your pneumatic equipment will operate efficiently and reliably. This step-by-step guide will provide a formula for calculating the necessary CFM for your air compressor.
What is an Air Compressor CFM Value?
CFM stands for cubic feet per minute and represents the measure of the volume of air that an air compressor can deliver at a specific pressure, making an air compressor’s CFM value a critical specification that greatly influences the performance and efficiency of your air compressor. CFM values are determined by several factors, including the size of the compressor, the size of the motor and the design of the compressor.
Some air compressor manufacturers refer to the CFM value as ACFM (Actual CFM) or FAD (Free Air Delivery).
Why Correctly Calculating CFM is Crucial for Your Operations
Because your air compressor powers pneumatic tools and equipment used for production, correctly calculating your CFM requirement and ensuring that your compressor can provide the proper CFM is essential to ensuring the best performance from your air-powered tools. If CFM is not properly calculated, it can negatively impact production.
If your CFM is too low
Your tools won’t receive the air they need to operate effectively, which leads to poor equipment performance, potential damage to pneumatic tools and an overheated air compressor because it will have to work too hard to supply the air demand.
If your CFM is too high
You’re wasting money. An oversized compressor uses more energy than necessary, driving up utility bills without any benefit to performance.
The Simple Formula for Calculating Your Minimum CFM Requirement
One of the easiest ways to calculate your CFM requirements is to use JHFOSTER’s CFM calculator.
Or, you can perform the calculations yourself following these steps:
Step 1: Find the CFM Requirement for Each Tool. Every pneumatic tool has a specific CFM rating as provided by the manufacturer. Check the tool itself, the product manual or the manufacturer’s website for this information.
Step 2: Add the CFM of all the Tools Used Simultaneously. To calculate your CFM requirement, add up the CFM requirement for each of the tools that will be operating at the same time.
Step 3: Multiply that number by 1.5 to Provide a Safety Buffer. To account for pressure drop and the initial air surge that tools experience upon start up, multiply the CFM number from step two by 1.5. This calculation would look like this:
(CFM of Tool 1 + CFM of Tool 2 + CFM of additional tools operating at the same time) X 1.5 = Your Minimum Required CFM.
| Using this methodology, a sample CFM calculation would be: |
| (CFM of all tools that will operate at the same time x 1.5) = Minimum CFM requirementFor example, if you have three tools that will operate simultaneously and each has a CFM requirement of 10, the calculation would look like this:(10 CFM +10 CFM +10 CFM) x 1.5 = 45 CFMIn this scenario an air compressor that has a CFM of 45 would be the MINIMUM CFM needed to power these three tools at the same time. |
Plan for Peak Demand and Future Growth
It could be recommended to add an additional 25% buffer to the minimum CFM calculation to account for the occasional peak demand and to allow for future expansion without needing to immediately replace your air compressor.
To add 25% to the calculation above, the formula would look like this:
45 CFM X 1.25 = 56.25 CFM
So, to allow for peak demand and future growth, a compressor rated for 56.25 CFM would be the ideal, long-term solution.
Don’t Forget the Pressure!
While the CFM calculation above can help determine the required CFM, it should be noted that compressors are not just rated for a specific CFM. Rather they are rated for a particular CFM at a specific PSI (or pounds per square inch), for example, 100 CFM at 100 PSI.
An air compressor’s PSI rating indicates the amount of pressure produced by a compressor per square inch of area and impacts the compressor’s ability to provide the right amount of pressure, or force needed for the job.
To better understand the relationship between CFM and PSI, it may help to think of CFM as the flow rate of a river (gallons per minute) and PSI as the water pressure. You need the right flow at the right pressure.
Therefore, it is important for performance and efficiency purposes that the selected compressor can produce the right CFM at the right pressure, or PSI.
To determine the necessary PSI for your facility, you do not have to find the sum of all the PSI values in the facility, instead simply use the PSI value of the tool that requires the greatest amount of pressure. Be sure to take pressure drop through the distribution system into consideration as the compressor will have to compensate for that when supplying the tool with its required pressure and flow.
To have an optimized air compression system, the compressor must be able to deliver the required CFM at the proper PSI. To ensure that this is the case, be sure to ask your air compressor supplier for the CFM rating (as mentioned earlier, this may sometimes be called the free air delivery FAD or ACFM rating) at the required pressure or PSI.
Ensure 100% Accuracy: Partner with a JHFOSTER Expert
While this formula provides an estimate of your minimum CFM requirement, a JHFOSTER expert can perform a full system evaluation to account for pipe design, pressure drop, system efficiency and energy rebates to design the most cost-effective and reliable system.
Don’t guess when it comes to a critical investment. Contact a JHFOSTER compressed air specialist today to schedule a comprehensive evaluation and get a quote for a system tailored specifically to your needs.
