If you are new to the world of pneumatic tools and air compressors, you may be wondering what exactly is air compressor CFM. The term is perhaps the most important factor in determining what air compressor will work with your air tools, so it’s important to make sure that you understand what you’re doing, and how to select the right compressor.
This is the amount of airflow that your air compressor is capable of producing. CFM stands for Cubic Feet per Minute, and this is the standard measure of airflow. The larger the CFM, the more powerful the air compressor is.
It’s important to know the CFM capabilities of an air compressor because different air tools have varying CFM requirements in order to function properly. If you are purchasing it for use with specific tools, they will be a great indication of the minimum CFM of the compressor.
- Frequently Asked Questions
- What is the difference between CFM and SCFM?
- What is CFM on an air compressor?
- What is a CFM rating on an air compressor?
- What CFM do I need for sanding?
- What CFM do drills and screwdrivers need?
- What CFM do grinders and cut off saws need?
- What CFM do I need for sandblasting?
- How do I find out the CFM of my air compressor?
- How to increase the CFM of my air compressor?
- Should I purchase an air compressor with a higher CFM?
- Does CFM increase as psi decreases?
- What size air compressor do I need to paint a car?
- How are compressors measured?
- How much air do you need to run an impact wrench?
- What is the best air compressor for spray painting?
- Now hopefully you understand what CFM means
Frequently Asked Questions
Here are some frequently asked questions that help you understand the term a little more, and to help you determine the best CFM for your specific needs.
What is the difference between CFM and SCFM?
CFM stands for Cubic Feet per Minute, while SCFM stands for Standard Cubic Feet per Minute. SCFM shows you the rate of airflow in a controlled environment (the temperature, humidity level and pressure is known).
Although there is some differentiation in what a controlled, standardized environment is between countries, it gives you a reasonable indication of what you can expect in certain circumstances. CFM has no standard to measure against.
What is CFM on an air compressor?
All air compressors will have a CFM number. This number indicates how much air flows out of your air compressor, in cubic feet per minute. The higher the air compressor’s CFM, the more power it can provide to your tools.
Every air tool will have a CFM requirement that your air compressor must meet in order for the tool to function properly. You should always make sure that your air compressors’ CFM is greater than the tools’ requirements.
What is a CFM rating on an air compressor?
The CFM rating on an air compressor is a number that determines its output – the amount of compressed air that flows out per minute. The CFM rating will also indicate at what PSI this flow rate is achieved.
Most commonly, the CFM rating is given at 90 psi and 40 psi, so that tool users can get a good indication of how the air compressor will work for their needs.
What CFM do I need for sanding?
The specific CFM that you need for sanding is going to depend on your sander. Each pneumatic tool has a CMF requirement.
In order to find an air compressor that can meet these requirements, you need to multiply the sander’s CFM by 1.5. As a general rule, you need an air compressor with a CFM of at least 5 – 6 @ 90 psi to ensure that you have enough power to use a sander. The MAC5200 Makita air compressor is a great example of a model that provides the right CFM for use with a sander, at 6.5 CFM @ 90 psi.
What CFM do drills and screwdrivers need?
The CFM requirements of a drill or screwdriver are going to depend a lot on the size of the tool. Smaller tools require less power and therefore less air.
A conservative estimate of a drill/screwdrivers’ CFM requirements for an air compressor is 4 or 5 CFM @ 90 psi, such as the PC1131 Senco air compressor. If you already have the tool and you want to buy the right air compressor to go with it, multiply the tools’ CFM requirements by 1.5.
What CFM do grinders and cut off saws need?
Tools such as grinders are a lot more powerful than other air tools and require a higher CFM to function correctly. Die grinders are smaller and can function when attached to an air compressor with a CFM rating of around 5 CFM @ 90 psi, such as the C041l Industrial Air compressor. An angle grinder is often larger and a more powerful type of grinder.
With angle grinders, you may need an air compressor with a CFM of up to 8 CFM @ 90 psi. These guides are very vague, so to make sure that your grinder and air compressor are compatible, always make sure to multiply the CFM requirements of your grinder by 1.5 in order to get an accurate minimum CFM for your compressor.
What CFM do I need for sandblasting?
If you are using a relatively small sandblaster, you can get away with using an air compressor with a CFM of 10 @ 90 psi, at the very least (like the VT6271 Campbell Hausfeld air compressor). In most cases, you will need something larger, closer to 20 CFM.
If you know that you have a much larger sandblaster that is capable of commercial-sized tasks, you may even need up to 30.
How do I find out the CFM of my air compressor?
Your air compressor should come with an indication of its CFM. If you cannot find this, or you are concerned that it may be inaccurate, you can determine the CFM manually.
First, you are going to want to completely empty the air compressor’s tank. Then, divide your tanks’ volume by 7.48 (if you had a 10-gallon tank, you would divide 10 by 7.48). The number you get from this equation is your tank’s volume measure in cubic feet.
Now you are going to refill the tank. Time how long this takes. You also need to note down the psig (Pounds per Square Inch in Gauge) number on your tanks’ gauge when the compressor begins refilling, and again when it stops filling and the compressor kicks out.
Take your final psig number, and subtract the initial psig number from when the compressor kicked in. Now divide the difference between 14.7, to determine the pressure that was added to the tank while it was being filled.
Multiply your tanks’ volume in cubic feet by the amount of pressure that was added while the tank filled up. This is how many cubic feet your tank pumped while it was filling up.
Now all you need to do is convert this number into minutes, to get the tanks’ CFM. Divide the amount of cubic feet that your tank pumped while refilling by the time it took to complete the refill. This is perfect for your air compressor.
How to increase the CFM of my air compressor?
If you need to increase the CFM then order to provide adequate power to a certain tool, you can do this to some extent. All you need to do is to decrease the pressure in the tank. You can achieve this by turning down the regulator.
Most air compressors are set at 90 psi, but you can lower this, which will in turn increase the CFM. This is because (power = pressure x CFM) so if your power stays constant and you reduce the pressure, the CFM will increase.
Should I purchase an air compressor with a higher CFM?
Yes, you should be looking at air compressors with a higher CFM when deciding what model to buy. Of course, CFM is not the only factor that determines a good air compressor, but you do need the CFM to be high enough that it powers your air tools.
As long as the CFM is great enough for that, you should be fine, and a CFM that is any higher will not damage your tools in any way but is also somewhat unnecessary.
Does CFM increase as psi decreases?
Yes, you can increase the CFM of your air compressor by decreasing the psi, which is the pressure in the tank. Most air compressors allow you to do this manually so that you can get the CFM that you need to power your air tools. You decrease the psi by turning down the regulator.
What size air compressor do I need to paint a car?
If you are looking to paint a car, you should get an air compressor with a CFM of at least 13. This will give you enough power to run the spray painter.
More importantly, you want to make sure that the air compressor has a large enough tank to contain sufficient air so that you do not constantly have to refill it. A great air compressor for this task is the Campbell Hausfeld air compressor with an 80-gallon tank, and 16 CFM @ 90 psi.
How are compressors measured?
Air compressors are measured by three main points: CFM, psi, and HP. As already discussed in detail, CFM refers to Cubic Feet per Minute and refers to how much air is flowing out of the compressor. Psi (Pounds per Square Inch) is the force that the air compressor can generate. HP stands for horsepower, and this refers to the capabilities of the air compressor’s engine. Together, these determine how well the air compressor performs.
How much air do you need to run an impact wrench?
Most impact wrenches require a CFM of at least 5 @ 90 psi in order to function. We also recommend that you get an air compressor with a tank capacity of at least 20 gallons, providing you with enough air to complete a job, so that you don’t need to stop and refill it. The DXCMPA1982054 DEWALT air compressor offers a 20-gallon tank and 5.7 CFM @ 90 psi, making it perfect for use with an impact wrench.
What is the best air compressor for spray painting?
If you want an air compressor to use for spray painting, you should look for something with a decent (at least 5 @ 90 psi), and a tank that is large enough to hold enough air without having to stop and refill. The 10020C California Air Compressor can provide 5.3 CFM @ 90 psi. It also has a 10-gallon tank which is large enough to get through the job but is still lightweight and easy to move around as you work.
Now hopefully you understand what CFM means
CFM is a term that you need to understand when purchasing compressors and we hope that this article has helped you to determine exactly what kind of air compressor you need to buy. Remember that the higher the CFM the better and the higher the CFM. The greater the chances that it will be suitable for a wider range of air tools.