Impact wrenches are powerful pneumatic tools that require a specific minimum CFM and air compressor to work with ease.

If you are wondering Will a 3-gallon air compressor run an impact wrench?

A 3 gallon air compressor cannot run an impact wrench. Even the smallest impact wrench requires a minimum of 1-1.5 CFM, so there will be inadequate pressure to supply the needed CFM to operate the tool. 

Unfortunately, 3-gallon compressors can’t meet the demands of an impact wrench. So in this article, we will help you find a small air compressor that meets the requirements you are looking for. 

Impact Wrench Air Pressure Requirements

Some people may think that you can use any pneumatic tool with any size air compressor. This is a very common misconception. In actuality, you need to look at the CFM rating on your pneumatic tool, in this case your impact wrench, and compare it with the ratings on your air compressor. 

What Is CFM?

Your impact wrench will have a CFM rating on it. In order for your tool to operate efficiently, you will need the same or more CFM coming from your air compressor. Generally you will need an air compressor that can put out 4 to 5 CFM @ 90 PSI to run a ½ inch impact wrench. The PSI rating is how many pounds per square inch the unit can put out. 

What Is PSI?

As stated above, the PSI is how many pounds per square inch the air compressor is capable of emitting. Essentially, it’s the force that a compressor can deliver air. Most pneumatic tools require between 70 and 90 PSI to effectively operate.

A light-to-medium-duty air compressor can accommodate 90 PSI, but you may want to have a compressor that can supply more flow then needed. If you have a tool that’s teetering on the edge of a rating, this is where the higher PSI will come in handy. 

What Is Horsepower?

The otehr factor you need to look at is horsepower. The horsepower is the amount of work the motor can perform.

It’s not as important as CFM and PSI, but it’s still a consideration to make. It’s important to remember than the more horsepower your unit has, the more energy it’s going ot use. The end goal with this is to do more with less horsepower to save energy. 

Impact Wrench Guide

Since there’s really no guide that gives you all of the specifications of every impact wrench, we will go over some of the most common sizes and the estimated air pressure requirements for each one. 

¼-Inch Impact Wrench

This is the smallest impact wrench that we could find. Since it’s smaller in size, you don’t need a ton of air pressure. If you have an air compressor that puts out between 1-1.5 CFM, you can operate the impact wrench with no issues. 

The DeWalt 6-Gallon Pancake Air Compressor would be a good choice for a ¼-inch wrench. It puts out 2.6 CFM @ 90 PSI and isn’t overly loud. You can use it in cold weather and on uneven terrain since it’s oil-less. 

 ⅜-Inch Impact Wrench

Since this is a tad bigger in size, you will need a more powerful compressor. You should look for a compressor that offers 3 to 3.5 CFM. Sure, you could use an air compressor with just 2.5 CFM, but it would prove to be inconsistent with pressure. 

As for the ⅜-inch wrench, we found the BILT HARD 8-Gallon Hotdog Compressor to be an optimal choice. It has a CFM rating of 4.0 @ 90 PSI. Its pneumatic wheels make it easy to transport the compressor as needed and it offers a quick recovery time. 

½-Inch Impact Wrench

The ½-inch impact wrench is the most common type that you will find. They fall in the middle of the size chart, so you will need to pay close attention to eh CFM rating of the air compressor.

You have many options when it comes to size. You can use a compressor that has anywhere from a 3.5 to a 5 CFM rating. You will want to be in the 4-5 CFM range though for better performance. 

As for the ½-inch wrench, the Stark 10-Gallon Air Compressor is an ideal contender. It offers 7.2 CFM @ 40 PSi and 3.5 CFM @ 40 PSI. Additionally, it’s 50% quieter than comparable models and offers optimal durability. 

1-Inch Impact Wrench

These are the big boys. They are generally only found on construction sites. Since they are so large and powerful, you’ll need a powerful air compressor to go with it.  You will want to invest in a compressor that offers a 9-10 CFM rating.

These are going to be a bit more pricey than the other compressors mentioned. You can take a look at these 60-gallon air compressors to see if any of them are a good fit for you. 

Air Compressor vs Battery Powered Impact Wrench

You will find that most mechanics and other handymen have used pneumatic impact wrenches for their various tasks. As technology advances, more and more individuals are leaning towards battery powered tools.

This has many people asking themselves if one is really better than other other. Let’s see if we can come up with a conclusive answer. 


When talking about impact wrenches, pneumatic versions have a clear advantage over battery powered wrenches; they weigh less. Since they rely on air for their power, they don’t have the extra weight that a battery would put on them.

Pneumatic wrenches don’t have an internal motor or a lot of wiring, so they have less meat insid whereas battery powered impact wrenches ate attached to a 2-lb battery and rely on a motor as well. 

High-torque impact wrenches can weigh over 8-lbs and a pneumatic wrench will only weigh 4.5-lbs. This is a noticeable difference and the weight of a battery powered impact wrench can take its toll on the users arms and wrists. 


As the years pass on, pneumatic and battery operated tools have had comparable numbers between the two.

The Milwaukee ½-inch cordless impact wrench can deliver 1,400 ft/lb of torque, with other models going up to 2,000 ft/lb, and the DeWalt ½-inch pneumatic wrench can deliver 1,200 ft/lb of torque.

As you can see, it may depend on the make and model of the tool. Otherwise, it seems that they are very close in torque range. 


No matter which type of impact wrench you choose, whether pneumatic or battery powered, there’s minimal maintenance. A cordless design has almost no maintenance requirements.

You simple need to have a charged battery. On the other hand, pneumatic tools require a little bit of oil. However, with pneumatic tools, you will have an air compressor which requires maintenance.

It has to be drained, oil need to be in it if required, the tank has to be free of moisture, and more. If you don’t want to go through the hassle of maintaining an air compressor, battery operated tools are the way to go. 


We can’t really talk about specific numbers since there are so many makes and models on the market, but we can tell you that cordless impact wrenches are more affordable than pneumatic impact wrenches, unless you already own an air compressor. If that’s the case, the tool may be just about the same price. 

When you purchase cordless impact wrenches, you will most likely purchase them with batteries. If the batteries are no longer working in the future, you will have to buy more, and they aren’t cheap.

With pneumatic impact wrenches, you will need to purchase an air compressor, the hose, and anything else you mey need. In the end, it may be more beneficial to purchase a cordless impact rather than a pneumatic if you don’t have a compressor. 


This one is a no brainer if you ask us. Cordless tools are much more convenient than pneumatic tools. With cordless tools, all you need to do is slap a battery on it and begin your task.

With pneumatic tools, you need to start up the air compressor, attach the tool to the hose, make sure there’s enough pressure, and you have to keep tabs on CFM and PSI to ensure maximum efficiency.

Additionally, cordless tools allow you to take your projects on the road without the hassle of lugging around an air compressor. This is perfect if you are a mobile mechanic. All you need to make sure you have are batteries and sockets.

The Takeaway

We’ve learned a lot from this article. We’ve learned that you cannot run an impact wrench witha 3-gallon air compressor. There is simply not enough CFM. However, you can choose just a bit of a larger size to run the smallest impact wrench on the market. 

Air compressors aren’t overly expensive if you don’t need anything too powerful. Additionally, it seems that cordless tools may be making a name for themselves.

However, if you’re still going to do things the old school way, then be sure to take another look at the compressors listed above.  You may be interested in our guide on Can You Paint A Car With A 30 Gallon Air Compressor