3/8 vs 1/2 Impact Wrench-Which Impact Driver?

We all know that having the right tool for the job can make a huge difference between things going smoothly and everything turning into a complete nightmare!

When it comes to trying to get rusty lug nuts off, deciding if you need a 3 8 vs 1 2 impact wrench is not always easy, but making the right choice will make it a lot easier.

There are loads of makes out there just to make it more difficult as well with great tools from Dewalt, Ryobi, and Ridgid to name just a few, but we’re going to bring it back to basics to help you make the right choice and look at the two most common sizes of impact guns – 1/2″ and 3/8″ and their key differences..

Let’s jump in!

What Exactly Is An Impact Wrench?

In the world of heavy-duty repair and maintenance work and the automotive industry, the repair technician’s life has been made so much easier with the arrival of impact wrenches. It has made it so much easier changing tires, undoing rusty bolts, and maintaining equipment in all areas of industry etc. forever.

Available in both corded and cordless powered versions they are known by several names such as air gun, torque wrench, impact gun, impactor, torque gun, air wrench, cordless impact ratchets, impact socket and probably a few more, but we’re going to stick to the simple name of impact wrench for our comparison.

Most corded and cordless tools come with a push-button system to start and stop the wrench, plus an LED light and some even have a display system to tell you what settings you’re using.

But what is it used for, you may ask?

Put quite simply, this powerful tool is used in many heavy-duty work industries like automotive work, mining, construction etc. to tighten or undo nuts, bolts, screws, and other types of fasteners.

They provide a huge torque output with little effort on the part of the operator by converting electrical energy into very strong rotational force, which is delivered through the shaft or driver of the wrench.

The driver comes in different sizes which is the part of the tool we’re looking at today. There are several tools to choose from ranging from 1/4″ up to a 1-inch version. 

Each one has its own benefits or drawbacks but as we know, the most popular sizes used today are either the 3/8″ or 1/2″ versions.

3/8 vs 1/2 Impact Wrenches

Now that we’ve gone through the basics of what impact wrenches are and what they’re used for, we can look at the differences between the two sizes.

The first thing to note of course is exactly that, the size!

The 3/8 or 1/2-inch size refers to the actual size of the driver’s diameter at the front, with the 3/8 inch version having a more compact design than the 1/2 inch one making it the better option to maneuver in tighter spots.

The downside of this is, of course, that you have less power at your disposal in the smaller-sized wrench as the driver will not be able to handle as much force going through it.

When you are weighing these up, think of the 3/8 driver as the best one to work within tight spots, where you need something not too heavy or bulky to get it into the right position. It’s great for delicate, precise work.

As a general guide, any nut or bolt that is less than 10mm or less will be best served by the smaller impact wrench but anything larger will require the 1/2″ sized driver with higher torque.

The 1/2 inch size is by far the most common impact wrench in use as it sits right in the middle of the different sizes available. It provides a good balance between precision and power and is the best option when you need a bit more oomph to tackle the job at hand.

Let’s take a look at how the two compare when it comes to actual torque.

What is the Torque Rating on Impact Wrenches?

It might be an idea to just take a moment and look at how we measure the power of these very useful tools before we carry on.

Manufacturers will always quote a maximum power rating that tells you how much rotational force or turning effect the impact wrench can apply.

In the U.S. this is usually measured in foot-pounds (which can be denoted as either lb-ft or ft-lb confusingly!) for larger values and inch-pounds (denoted as in-lb) for smaller values.

Often you will also see two ratings such as on the very powerful DEWALT DCF899HB 20V MAX XR Brushless High Torque 1/2″ Impact Wrench which quotes the standard 700 ft-lbs of maximum force but also has 1200 ft-lbs of breakaway torque rating.

The breakaway figure is the amount of force it can apply when undoing a seized bolt and is very useful to know if you need more power.

How Powerful is a 3/8 Inch Impact Wrench?

As we mentioned previously, the smaller size will have less power but that can be a good thing when you’re dealing with delicate nuts and bolts!

As an example let’s look at the popular DEWALT 20V MAX XR Cordless Impact Wrench, 3/8-Inch (DCF890B) which has a very usable 150 foot-pounds of torque.

That’s probably the top end of power available on 3/8 inch cordless tools, so you should expect to find one with between 90 and 150 ft-lbs when looking for a new impactor. 

So How Much Power Does a 1/2 Inch Version Have?

With the larger driver, the 1/2 inch tools can work with a lot more torquing so you should expect to find anything from around 150 ft-lbs to something like 700 ft-lbs at the top end, such as on the Dewalt DCF899HB referenced above, great for heavy-duty projects and has amazing breakaway torque values.

Unless you need that massive torquing power of the Dewalt, then something like a Ridgid R86011B OCTANE 18V Lithium-Ion Cordless 1/2 Inch Impact Wrench which has a max rating of 450 foot pounds is the sort of thing you should look out for on a good cordless impact tool.

When it comes to comparing a 1/2-Inch vs 3/8-Inch impact wrench, that extra step on the size chart makes a big difference for heavy-duty project work.

Which One Should You Use?

As you can see above, different sized wrenches work with different power so you need to figure out which one would work best for you and not pick the wrong tool.

Also bear in mind that the 1/2 inch driver is going to be considerably bigger and heavier than a 3/8 inch compact stubby version.

It’s important to make sure you match the correct power output to the job you’re working on as you don’t want to risk damaging your tools or the material you’re working with by using too much torque. For example, using a 1/2 inch wrench driver with 1200 ft lbs of breakaway torque to undo a small 10mm nut is probably going to result in stripping the bolt thread or rounding off the nut.

On the other hand, trying to undo a rusted lug nut on car suspension bolts with a 3/8 inch cordless torque wrench may just wreck the driver as it will struggle to apply enough force to get the nut off. 

The more compact size of the lighter 3/8 stubby impact wrench is great for working in tighter spaces with limited room to get at the nut or bolt you’re working on. It’s great for effortlessly removing bolts up 10mm and allows for more precise control when working with smaller fasteners around the house.

On the other hand, if you require a bit more power to safely remove seized nuts and bolts without having to apply too much effort then the 1/2 inch version is the one to go for as it can be used as multiple tools in one.

Let’s go through a few FAQs that we’ve had on impacters:

Will a 3/8 Inch Impact Wrench Remove Lug Nuts?

If you come to do your tire rotations and find you have a seized lug nut then you will need a power tool to get it off.

If you only have the 3/8 Inch tool to hand it’s definitely worth a try and will do the job if you use the proper sockets and as long as it has enough power, but of course a 1/2 inch would make a better job of it with a higher level of torque.

Impact Driver vs Impact Wrench – What’s the Difference?

This is something that can be confusing when looking at impact wrenches.

You may well come across a range of tools called impact drivers and wonder if this is the same thing.

The answer – sort of, although they tend to be less powerful, they can do the same sort of job. In fact, there are some impact drivers available now that have higher power, such as the Milwaukee 2853-22 M18 FUEL 1/4″ Hex Impact Driver which has a rating of around 160lb-ft of torquing force!

The main difference is that impact drivers tend to come with a 1/4″ drive and are intended for more precise work in tight spaces.

Can I Use Extensions With My 1/2 inch or 3/8 inch Wrench?

Yes, you can use extensions that will help to get at those hard-to-reach bolts, but you will experience a loss of torque. How much will depend on the length of the extension and whether they are impact-rated.

As a general rule, do not use non-rated accessories, such as chrome sockets, with your impact wrench as they could shatter under the immense load placed on them. This could invalidate your product warranty as well so take note.

The impact extension and impact 6 point sockets that are properly rated will lose less power and are manufactured to withstand being used at high torquing settings.

Conclusion – How Do I Choose an Impact Wrench?

Many people will buy one of these so that they can loosen those seized lug nuts that are in places where you can’t get a breaker bar to fit. If that’s you then the lighter 3/8 inch stubby impact wrench will do the best job as its compact size allows you to use your sockets in tight spaces.

This would also be best for general use around the home as it works well with fragile bolts and the smaller sizes of fasteners you get in the house and where you require precision..

However, if you need to tackle bigger jobs like seized suspension bolts and other suspension work, then the 1/2-inch impact gun will soon become your best friend in the workshop. Although not meant for constant professional use, they are a powerful impact wrench that can be used for most jobs in the workshop and around the home.

If we had to choose one size, it would probably be the 1/ 2-inch impact wrench as it can do pretty much everything and is in the middle of all the sizes.

The best plan would be to get both, then you can just choose the right tool for the particular job you’re doing at that time!