Impact Wrench Sizes. What Size Impact Wrench Do You Need?

Impact wrenches are one of the most useful tools that you can have in your arsenal. They are great for working on construction projects, scaffolding, cars, trucks, mowers, and just about anything else that you can think of. However, you have to make sure that you have the right size for the right job. In this article, I’m going to tell you everything that you need to know about impact wrench sizes.

The Different Sizes of an Impact Wrench

Impact wrenches come in various sizes, and as you might have guessed, the size of the wrench and its socket can have a massive impact on what jobs the wrench is able to tackle.

What is the size of an Impact Wrench?
First, let me explain what you mean by the size here. The size of an impact wrench is the dimension of the drive anvil.

Impact Wrench Size
The size of the impact wrench is the distance between the flat edges of the driving anvil.

In this section of the article, I want to introduce you to some of the most common sizes that you will see when out shopping for an impact wrench. For quick reference, these are the sizes that you will see if you were to go to any hardware store and look for impact wrenches: 1/4-inch, 3/8-inch, 1/2-inch, 3/4-inch, and finally, a full 1-inch.

Before moving on though, I want to briefly explain in a bit more detail what each of these sizes is good for and how common they are.

1/4-inch and 3/8-inch

By far the smallest impact wrenches that you can find are 1/4-inch and 3/8-inch wrenches. These small wrenches are generally pretty compact and very easy to use in extremely tight spaces. They come in a variety of different styles, including both pistol grip and inline grip styles.

These are perfect for bolts that are 10mm in diameter or below. They are also perfect for working in situations where accuracy and precision trump power.


Probably the most common size of impact wrench is the 1/2-inch impact wrench. The reasons for this are pretty obvious, especially if you have used these power tools a lot before. Because 1/2-inch impact wrenches are in the middle of the size chart, they offer the best balance between precision and power.

1/2-inch Impact Wrench
A digital vernier caliper measuring the size of a 1/2-inch impact gun.

On the one hand, you can use them to safely remove nuts and bolts without fear of applying too much torque and causing damage. On the other hand, this size of impact wrench tends to actually have enough power to do a wide variety of jobs, including those that smaller, less powerful impact wrenches can’t.

3/4-inch and 1-inch

Finally, we come to the two biggest sizes on the size chart, 3/4-inch, and 1-inch wrenches. Of all the sizes, these two are the least common. The reason for this is that they tend to be so powerful that they aren’t particularly useful for most home projects. However, take a walk over to your local construction site, and you will start seeing a lot more 3/4-inch and 1-inch wrenches since their power is a lot more useful in a professional setting.

While this quick guide to the various sizes of impact wrench is certainly useful, I don’t want to just stop the article there. So, to help you out even more, let me go over some of the more common jobs that you will use an impact wrench for and explain what size wrench is good for each job.

What Size Impact Wrench to Use for Each Kind of Job

The three common jobs that I’m going to talk about in this section are dealing with lug nuts (both installation and removal), auto repair, and removing and installing lawn mower blades. Obviously, this is just a small fraction of the tons of different jobs that you can do with an impact wrench. I just want to show you the sorts of things that you should be considering when trying to determine what the right size impact wrench is for a specific job.

What Size Impact Wrench for Lug Nuts?

Alright, so let’s say that you have to remove some old lug nuts and add in some new ones. This is a pretty common job if you work on vehicles or do your own vehicle maintenance. Or you just want to replace the flat tire with a spare one. I do this a lot and I’m sure many of you reading this also do it. What size impact wrench is the best for this sort of job?

I recommend staying near the middle in terms of size. So, go for either a 3/8-inch impact wrench or even better, a 1/2-inch impact wrench. These are the best sizes because they offer enough power to get even very tough lug nuts out, but at the same time, they won’t apply too much torque. You want to be careful about applying too much torque because you could end up stripping the lug nut. Trust me when I say that doing that will make your life a lot more difficult for no reason.

A lot of people ask me if they could use an impact driver to remove lug nuts. While it is possible with the modern power tool, an impact wrench or a breaker bar and a torque wrench are the right tools for replacing your car tires.

What size impact wrench for changing tires?

The ½-inch impact wrench is the best size for changing car tires.

A 3/4-inch or even a 1-inch impact wrench could be an option, but unless you are working on a big truck, construction site or in a commercial setting, it’s a bit overkill. I definitely recommend sticking with either the 3/8-inch or 1/2-inch option.

Impact Wrench Size for Automotive Work

When it comes to working on your automobile, the best size is going to be dictated largely by what kind of vehicle you own. For most regular-sized vehicles, a 1/2-inch impact wrench should have more than enough power and flexibility to handle working with the vehicle. At that size, the impact wrench will have enough power to do whatever job you need it to do. At the same time, a 1/2-inch impact wrench isn’t so big that you will have issues maneuvering with it.

If you have a very big vehicle or a truck of some sort, then you may find a 3/4-inch impact wrench to be the better option. An impact wrench of this size will be more powerful and will be better able to handle the very large components found inside bigger trucks.

Impact Wrench for Changing Lawn Mower Blades

Finally, another very common job that you need an impact wrench for is changing lawn mower blades. Now, if you still happen to own your lawn mower manual, then you can find out from there what sort of tool is needed to change the blades. It should give you the exact specifications. If, however, you are like me and don’t have the manual that’s okay.

When it comes to changing lawn mower blades, you don’t need a lot of power. Instead, what you need most is precision. The type of precision that you need for changing lawn mower blades is only possible if you use smaller impact wrenches. For this reason, I would recommend going with either a 1/4-inch impact wrench or a 3/8-inch impact wrench. These will be small enough to do precise work, while still being powerful enough to easily get the old blades out and the new ones in.

Alternatively, you can go for an impact driver which has torque control. But you will need to use special socket adapter since impact driver usually has a ¼-inch hexagonal socket.

Recommended Impact Wrench Size

In my opinion, a ½-inch impact wrench is the best size for most people. It has enough power to get most of your DIY, home repair and is suitable for a variety of professional work as well.

Whatever size impact wrench you chose, always get the right size impact socket with it. Never try to use the regular chrome socket on an impact tool.