How Do I Find Out What Size Air Compressor Do I Need For Impact Wrench?

We all know that different pneumatic tools come with different air compressor requirements. For the same reason, the air compressor needs to fulfill minimum size criteria for running each tool. Today I stumbled upon the question, what size air compressor do I need for impact wrench?

The size varies depending on the impact wrench’s size. There are three aspects to consider- air pressure, CFM rating, and tank size. For a ½ inch impact wrench, you’ll need an air compressor featuring 90 PSI air pressure, 3 to 4 CFM rating, and a 20-gallon tank.

Like I said, the size requirement will vary depending on your tool’s size. Keep reading through to get all your answers about impact wrenches and air compressors.

What Is An Impact Wrench

What Is An Impact Wrench?

An impact wrench is a tool that transfers kinetic energy to tighten or loosen large bolts, lug nuts, and frozen fasteners. If you’re wondering how an impact wrench works, the process is pretty easy to imagine.

Suppose you are trying to loosen a really tight screw. The screw is so tight that even a wrench won’t loosen it, let alone your hands. Now imagine you are using a hammer to hit the wrench, and the screw turns.

That’s exactly what your impact wrench does. It draws power from your air compressor and uses the power to operate the hammering mechanism.

Uses Of A Pneumatic Impact Wrench?

The most common use of an impact wrench is removing or attaching lug nuts. Have you seen the nuts used on your car tires? Those are called lug nuts.

When changing tires, impact wrenches are used for removing and re-attaching those nuts. Other than that, assembling any large machines can require an impact wrench.

What Size Air Compressor Do I Need For Impact Wrench?

As you may already know, air compressor size for any tool is determined using three components. Air pressure, that’s indicated using a unit called PSI, CFM means the mass volume of air a machine can deliver per minute and the tank size.

  • Air Pressure

Air pressure in compressors is measured using PSI that stands for Pounds per Square Inch. Like most other pneumatic tools, impact wrenches work with 90 PSI air pressure. But the pressure can vary depending on what size wrench you are using.

The range won’t deviate too much, though. You can use any size impact wrench between 90 to 125 psi air pressure.

  • CFM Rating

The CFM rating required for different size impact wrenches can vary between 2 to 16. CFM plays the most vital role when it comes to determining air compressor size. All wrenches may run on the same PSI level, but the CFM varies from 2 up to 16.

When you’re using a ¼ inch impact wrench, an air compressor with 2 CFM will suffice. In comparison, when operating a 1-inch impact wrench, you’ll need an air compressor with 16 CFM.

  • Tank Size

The smallest tank size that can run an impact wrench is 6 gallons. But that’s the lowest bar. It’s safe to go for a 20-gallon tank compressor because, let’s be honest, you won’t use your air compressor only for running an impact wrench.

Ideal Air Compressor Size For Different Size Impact Wrench

As I’ve already mentioned, impact wrenches come in different sizes. And, the size requirements vary depending on wrench sizes. Let’s dive a little deeper.

  • ¼-Inch Impact Wrench

Being the smallest size in impact wrenches, a ¼ inch impact wrench won’t require a large CFM air compressor. Air compressors delivering 1 to 1 ½ CFM will suffice. Even though you can use a compressor with higher CFM, it’s not compulsory.

The minimum air pressure for most tools, including this one, is 90 PSI. You’ll need an air compressor that at least features 90 PSI air pressure.   

  • 3/8-Inch Impact Wrench

If we compare a 3/8 inch impact wrench to the prior one we discussed, it needs 2x CFM. You will need a compressor that can deliver at least 3.5 CFM. Note that you can go for a lower CFM air compressor, but it’s better to be on the safer side.

What I’m saying is you can operate a 3/8 inch impact wrench using a 2.5 CFM air compressor, but if you’re buying a new compressor, it’s always better to go for a higher CFM than staying on edge. As for the air pressure, this too can run on 90 PSI.

  • ½-Inch Impact Wrench

Half-inch impact wrenches are most widely used and one of the most common tools. When someone asks ‘what size air compressor do I need for impact wrench,’ they’re usually referring to a ½ inch impact wrench.

A compressor ranging from 3.5 CFM to 5 CFM can operate a ½ inch impact wrench smoothly. It would be wise not to cut it close by purchasing a 3.5 CFM air compressor. If you’re buying one, a 4 CFM compressor might be the safest bet.

Suppose you want to go for a higher CFM air compressor, much better. If we’re talking about air pressure, it’s better to go for at least 90 to 100 PSI.

  • ¾-Inch Impact Wrench

A ¾ inch impact wrench will need an air compressor of around 7 CFM to operate smoothly. As for air pressure, it should be about 90 to 100 PSI.

  • 1-Inch Impact Wrench

Even though it’s highly unlikely that you’ll be using a 1-inch impact wrench, there’s no harm in stating the facts. These wrenches are mostly suitable for construction sites and can hardly be found in average houses.

If you need to use such wrenches, know that they’ll require powerful compressors. These wrenches can require from 10 to 16 CFM and 90 to 125 PSI air pressure.

Impact Wrench Size

Air Compressor Size Chart For Impact Wrenches

Impact Wrench Size


Air Pressure (PSI)

¼ inch



3/8 inch



½ inch



¾ inch



1 inch



Why Use A Pneumatic Impact Wrench?

If you didn’t already know, there are three types of impact wrenches. One that runs using an air compressor, one that runs on a battery, and one that runs using electricity. Among these three, a pneumatic impact wrench is most popular among users.

Why? Because it comes inexpensive. That’s the first reason. The second reason is, using air for operating the wrench makes the tool cooler compared to other methods.

Another reason I must mention is the longevity of the tool. If you compare durability among these three, an air impact wrench will undoubtedly take the cake.

There’s also a downside of using an air compressor-powered impact wrench, though. You’ll have to make sure that the tool is getting uninterrupted compressed air. Or else the tool will shut down.

But that’s a very solvable problem. Choosing the right size air compressor will immediately solve this issue. I mean, that’s what the whole article is about.

Torque Wrench Vs. Impact Wrench

Many users ask this question, why not use a torque wrench instead of an impact wrench? The answer seems pretty obvious to me. Even though both tools can perform a few similar functions, they aren’t the same.
To clear any confusion, let me put some light on how one differs from the other. A torque wrench is a manual tool. You have to use your hands and your own energy to use the wrench.

An impact wrench, on the other hand, will draw power from your air compressor. So, which one do you think is the appropriate one to use?

Let’s talk about some pros and cons. Without any doubt, a torque wrench will cost less than an impact wrench. But, impact wrenches are also very affordable.

If you use a torque wrench for quite some time, you’ll eventually feel fatigued. Impact wrenches, on the other hand, won’t cause you any physical discomfort given that you’re following all safety measures (eye and ear protection).

One advantage you get with a torque wrench is precision. Compared to an impact wrench, a torque wrench will give you more precise torque control. Other than that, an impact wrench is better in every way.

Things To Keep In Mind

Remember the following things before buying, using, or altering any power tools or air compressor.

  • Recommended CFM

Different air tools have different recommended CFM ratings. Even two same size impact wrenches made by different manufacturers can have different CFM recommendations. Check the user manual for your tool’s recommended CFM.

If you somehow lost your user manual, contact your manufacturer. If that’s not possible either, consult a local professional to find out the CFM.

  • Recommended CFM And Required CFM Are Not The Same

Remember that your tool’s recommended CFM is not the same as your air compressor’s CFM requirement. Then how to calculate the required CFM for your air compressor? It’s easy.

You have to multiply the impact wrench’s recommended CFM by 1.5. Suppose your wrench’s recommended CFM is 2. Then your air compressor must have at least 2 x 1.5 = 3 CFM rating.

  • When Buying A New Compressor

Always go for features more than you need. It’s better not to cut it close. Moreover, buying a higher capacity compressor only by adding a few more bucks to the budget will let you use the same machine for different purposes.

You may not need to use the machine for other tools right now, but you don’t know for sure that you won’t. It’ll cost you more in the future to buy another air compressor.

Why Using The Right Size Air Compressor Is Important

When you operate your tools using the recommended settings provided by the manufacturer, they last longer. The manufacturers will suggest to you the settings optimal for the tool to use. If you don’t exceed those settings, your tools don’t have to go out of their way, and the chance of wearing them out reduces.

You also protect your air compressor by using the recommended settings. The more you follow the rules, the less your machine gets heated, the more power it can offer.

Other than longevity, your tools run more efficiently when working inside their comfort zone, i.e., their recommended settings.

Safety Measures For Using An Impact Wrench

  • Understand your tool by going through the user manual thoroughly. Don’t miss anything. Follow any special protocol advised by the manufacturer.
  • Check if you’ve assembled everything properly. Any loose ends can lead to unwanted situations.
  • Use safety glass for not only impact wrenches but all power tools.
  • Cover your ears because your tool and compressor both can make noise up to the annoying level.
  • Avoid wearing any jewelry, loose clothes, tie, etc.
  • If you have long hair, tie them securely before starting your air tool.

Before altering any settings on your impact wrench, make sure you’ve disconnected it from the air compressor.

What Are Others Saying?

Frequently Asked Questions

Q: Can I run an impact wrench with a 3-gallon air compressor?

No, you can’t. The smallest air compressor owned by DIY lovers features a 3-gallon tank. However, you need at least a 6-gallon air compressor to run even the smallest impact wrench.

Q: Should I buy a 6-gallon air compressor to run my impact wrench?

If you’re purchasing the machine solely based on operating an impact wrench, you can buy a 6-gallon compressor. However, purchasing a 20-gallon compressor will let you use other air tools without having to stop midway.  

Q: What tank size do professionals use when operating impact wrenches?

Professionals are more efficient with their tools, so they need continuous air supply. Most professionals will prefer a 50 or 60-gallon air compressor to operate their impact wrenches.

Final Verdict

Hopefully, you got your answer to the ‘what size air compressor do I need for impact wrench’ question. Don’t worry about it. We all get a bit confused sometimes. That’s what got me to do my research on this topic in the first place.

But whatever you do, remember always to follow the safety protocols. If you’re not a professional, using power tools without any knowledge can often lead to accidents. Be smart and keep yourself updated. But also, keep your safety on top of the priority checklist.

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