Air compressors are one of those things most people don’t think they need. Until they have one and realize they should have had one all along.

If you have cars, bikes, a workshop or hobby shop, and certain types of tools, toys, and various other things, you should have an air compressor. This air compressor sizing guide will help you choose what type and size you need.

Choose an air compressor based on the requirements of your tools, tires, etc. Pick the one with the highest cubic feet per minute (CFM) at the highest pounds per square inch (PSI). Base the size of your air compressor on the highest CFM needed plus 50%.

Read on, and I’ll provide tips on how to pick the right size and type of air compressor.

How to Pick the Right Size Air Compressor

The specifications of the air conditioner can be confusing, so let’s talk about a few of them first.

Air pressurePSIand flow rate—CFM—are measured in relation to one another.

CFM

CFM or cubic feet per minute is a measure of volume—the speed that an air compressor supplies air. This is typically the most important specification you should pay attention to. Smaller, portable home air compressors typically deliver around to CFM while industrial compressors can achieve about 1,000 CFM.

In either case, CFM is measured at a specific PSI.

PSI

PSI, or pounds per square inch, is the number of pounds of pressure exerted on one square inch of space. For example, 100 PSI is equal to 100 pounds of force on one square in.

Your air compressor needs to be able to supply sufficient airflow—CFM—at the right amount of pressure—PSI.

What Size to Buy

As mentioned above, looking for an air compressor that supplies about 50% more CMF than your item needs is a good idea, but that isn’t an ironclad rule. But it does allow for room to grow and a margin of safety.

Buying a compressor that will only work on your largest item means it will be of no use to you if you ever buy or acquire something that needs more CFM.

For example, if you currently own a small brad gun and have a compact compressor with a 1 HP motor and 2 CFM, it will do just fine. If you ever need to move up to a larger gun and nails, or you want to run more than one gun, your compressor will be too small.

What Type of Air Compressor do you Need?

Before figuring out what size you need, you should be thinking about what type of air compressor you need. Your application, or what you plan to use it for, dictates the type you need.

There are two popular types of air compressors—reciprocating or piston air compressors and rotary screw compressors. However, there are also scroll turbo styles, but they have specific applications, typically industrial.

Air Compressor Types
There are many different types of air compressors, each with its own unique capabilities and drawbacks.

Reciprocating Compressors

This style of compressor compresses air with at least one cylinder and piston. The pistons move up and down within the cylinder to compress air.

Some features of reciprocating compressors include:

  • A wide range of pressure
  • Low capacity
  • Have been designed for intermittent use

These compressors are typically small in size and are good for the following:

  • Garages
  • Home renovation projects
  • DIYers
  • Workshops

Check this out if you want to take a deep dive into how reciprocating compressors work. 

Rotary Screw Compressors

This type of compressor works by using two screws or meshed rotors that turn in opposite directions inside the compressor housing. Air is compressed when it gets trapped between the rotors.

Rotary screw compressor features include:

  • They are low in pressure, with a maximum of 215 PSI
  • High capacity
  • Designed for continuous use

These are larger machines. Thanks to their lower volumes or compressed air, they’re used for things like tires and power tools. But they may be the best option for your attached garage.

If you’d like to delve a little deeper into how this type of compressor works, check out this detailed guide.

List of Specific Sizes and Applications

If all of the above is too much and you just want to know what size air compressor you need for a specific job, we’ve got youcovered. We can’t list every possible scenario here, but the following is a list of common uses.

Note that this list is geared toward homeowners, not industrial applications.

Car Service Air Compressor
Air compressor tank size matters.

So, what size air compressor do you need for:

Automotive Air Tools

Find the total necessary CFM requirements for all your tools.

For example, if you have a selection of tools that require 70 CFM—which would be normal for a small shop—you’ll need a compressor capable of that at minimum. You can size up from there—as mentioned above, some suggest upsizing by 50% but that’s your choice.

Automotive Paint Gun Guns

Paint sprayers for your car will require about 12 CFM max at 45 PSI.

Brad Gun/Nailer

These guns only require minimal air volume. 1 CFM at 60 PSI for the smallest size, but depending on what you have you may need up to 90 PSI.

Car Tires

If this is your only application, a small portable compressor will do. Your passenger vehicle tires will require one that can handle 35 PSI.

Note that CFM doesn’t apply to car tires since they have valves.

Flooring Nail Gun

Flooring nail guns require a 4 CFM air compressor. That amount, paired with a good PSI will ensure your nails are driven to depth.

Framing Nail Gun

Finally, getting around to finishing your basement? At maximum, you’ll need a framing nail gun, which calls for 4 CFM at 60 PSI. 

Garage

When sizing an air compressor for your garage, take into consideration what you’ll need it for. Once you know the maximum CMF you’ll need, work from there.

For example, what is the largest—at least in terms of air requirements—thing that needs air? Are you going to be using an angle grinder to cut and finish a lot of tiles? Then you need a compressor that can supply a maximum of 6.5 CFM at 90 PSI. You could just use that number and buy accordingly, but a better idea is to round up several CFM for some future applications that might be a bit bigger.

Impact Wrench

If you’re working with lug nuts and have a ½-inch, you’ll need enough torque and about 4 CFM of compressed air. ¾-inch lug nuts will require 7 CFM.

Staple Gun

If you have a heavy-duty staple gun it will require at least 4 CFM at 90 PSI.

Conclusion

Having an all-purpose air compressor in the garage is a wise choice. Just be sure to add up all the things you would use it for—and by add up I mean add the CFM for each appliance. And then round it up.

The good news is there’s lots of selection when looking for a compressor, especially a reciprocating compressor. So even if you know you’ll never need one for anything but a select few applications, you can choose a size based on that.

Hopefully, the info here has helped you in making a choice! While you’re here, why not check out our related posts below? Perhaps we can help you with something else.