Last updated: September 3, 2021

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It may be that impact wrenches are not the most common tools, but that doesn't mean that they're not useful. These tools have become very handy for DIY-lovers, but even more so for professional mechanics, who work continuously with nuts and bolts.

An impact wrench lets you loosen or tighten a nut more easily without struggling or straining. Using these tools also helps to avoid crushing the nuts, making them useless. This article will cover everything you need to know about these powerful tools so you can choose the one best suited to your needs.

Key Facts

  • Impact wrenches' power comes from their torque, measured in Newton-meters (Nm). It is important to have the right power to loosen any fixing element we work with.
  • Unlike other tools, impact wrenches are usually only found in workshops, as they are very powerful tools. However, new models are very versatile and suitable for all budgets.
  • The size of the cup or mouthpiece is as important as its design or feeding. It is a decisive factor in an impact wrench, as it will define the type of nuts you can work with. Our recommendation is to choose an interchangeable one.

Our Selection of the Best Impact Wrenches

Impact wrenches are often found in mechanics' workshops but are versatile tools which can be equally useful for DIY, amateur mechanics and construction. In order to help you make the best selection, we've pulled together a list of the best impact wrenches on the market.

Shopping Guide: Everything You Should Know About Impact Wrenches

Impact wrenches have been associated with car and tire repair for a long time. Although it is a very common tool in this type of work, you will also find it in other fields such as steel, mining and aeronautics. Please find below our shopping guide for impact wrenches.

mechanic fixing a car

Impact wrenches are commonly used by mechanics.
(Source: Antonio Diaz: 20408465/

What is an impact wrench?

Impact wrenches were introduced to the market about 75 or 80 years ago and have not changed all that much since then. Their appearance is similar to a drill, but unlike that tool, which works using rotation energy, impact wrenches are designed to provide high torque at low speed.

Unlike drills, impact wrenches do not generate a constant torque. They could be said to work in a similar way to placing a manual wrench on a nut or screw that we want to loosen and hitting the wrench with a hammer, making it turn by short and gradual sections.

How do impact wrenches work?

When they receive energy, an internal "hammer" strikes an anvil that is connected to a shank mandrel (which can be square or hexagonal) in the nozzle. This produces a rotation in the socket wrench connected to the mandrel and such rotation is used to tighten or loosen the nut.

This hammering action is its main advantage versus similar tools, since it achieves two important effects that a drill cannot. First, it exerts much more force and second, hammering action tends to loosen rust and other deposits keeping nuts or bolts adhered to the surface, hindering its extraction.

Pneumatic impact wrench gun

Impact wrenches are made to achieve high torque at low speeds.
(Source: Mikhail Gnatkovskiy: 103162718/

What advantages are there to using an impact wrench?

The three main advantages of the impact wrenches are: high power in a compact size and reduced weight tool, speed and most importantly, the lack of reaction, which is the force that tends to turn the machine and the operator's wrist when the machine delivers power to the head. This means this tool is very safe and easy to use.

Although the first models of impact wrenches were heavy and only had one sense of rotation, today these machines have evolved and are very compact. Most modern models work with battery and you can take them in the trunk of your car, allowing you to make an emergency tire change in a few minutes.

What types of impact wrenches are there in the market?

As we have explained, you can currently find a wide variety of impact wrenches in the market. You will find manual, pneumatic and electric models, with both cable and battery power. Each model has its own features and is indicated for a specific type of work.

Next, we will see each of the impact wrenches in greater detail:

Type of impact wrench Characteristics
Manual Original wrenches.

They work with a hammer.

Although electric versions are much more comfortable, manuals wrenches are still a good choice for DIY works.

Pneumatic They work with compressed air and must be connected to an air compressor.

They have a large air consumption, so they need large compressors.

They have different sizes and powers.

Most modern versions have ergonomic designs to reduce operator’s fatigue.

They do not have a regulation trigger.

Ideal for regular and large bolts.

They work very well with rusty bolts.

They should not be used with small nuts, as they will break them.

Electrical with cable Power similar to pneumatics, but inferior.

Slightly larger than pneumatic ones due to the engine space.

They do not need a compressor.

They have a regulating function on the trigger.

Cordless electric Currently the most popular.

They allow incorporating accessories for bolts of different sizes.

Ideal for working in confined spaces, for example, in car engines.

They are powered by 18 to 28 volt (V) lithium-ion batteries.

Less powerful than cable or pneumatic versions.

When not frequently used, the life of the battery gets depleted.

Very portable.

They are the best option for very tight or rusty screws.

How many revolutions per minute does your impact wrench need?

Although it will largely depend on your needs, an ideal speed for an impact wrench is 3000 revolutions per minute (RPM) or more.

As we have already explained, the operation of these tools is based on rotations to tighten or loosen fasteners. More rotations means less effort from the user.

Lower speeds can take longer to finish your task, so if speed is a requirement for your work, it is a good idea to choose an impact wrench with high speed and RPM, even when you have to sacrifice some pressure torques or impacts per minute, it will be worth it in the end.

What are impacts per minute (IPM) and how do they affect impact wrenches?

The number of impacts per minute (IPM), as well as the speed, must be high enough, since impact guns require a lot of contact to act on a fastener in order to tighten it or loosen it. If you can’t buy a wrench with a high IPM, look for one with a good balance between torque, speed and IPM.

Having a higher IPM means there will be more contact between the tool and the fastener. A greater contact means the element will remain in place more firmly. If you add this to considerable torque and speed values, you will get an almost perfect impact wrench.

Close up shot of the hands of mechanics using pneumatic wrench t

There are many different types of impact wrenches, so it is a good idea to choose that which suits your needs. (Source: Nakhorn Yuangkratoke : 65219844/

What uses and applications does an impact wrench have?

Impact wrenches have become very popular, especially since the creation of battery models. As it is a portable tool, its uses have been considerably multiplied. This makes them excellent road or garage mates. You will also see them in spaces under construction where there are no power outlets.

Application Characteristics
Car Impact wrenches have always been used for car repair and assembly.

Battery models are an ideal car complement, especially for an emergency, such as a tire change.

Battery models are better than manual models, since there is no risk of twisting your wrist in the middle of a long trip.

Mechanics garages Impact wrenches have always been a part of mechanical workshops.

They quickly and easily tighten nuts and bolts.

Battery models allow mechanics to work in narrow places like engines.

Carpentry and decor Many furniture require using screws and bolts for assembly.

Impact wrenches perform this task in a very easy way.

Electric impact wrenches ease the removal of rusty bolts in outdoor assemblies.

Domestic use Many furniture and appliances contain nuts and bolts.

An impact wrench can be very useful for home repair works, like changing a sink, for example.

How do you use an impact wrench?

Now that we have explained everything you need to know about impact wrenches, their most important features and uses, it’s time to see how these powerful tools are correctly used so you can get the maximum performance and avoid accidents and injuries.

Next, we explain step by step how to use an impact wrench:

  • Check manufacturer’s manual. This first step is very important; never use a tool without checking manufacturer’s manual first. You have to get familiar with the tool and its main features.
  • Connect the wrench. In the case of being wireless, connect the battery to the charger and wait for it to be fully charged. In the case of electric models, connect the cable to the current. Some models turn on automatically, while others have a switch.
  • Select a head. Depending on the size of the nut you want to loosen, you will have to place the appropriate wrench. Once the right head was found, firmly tighten the square socket of the wrench. Never change a head if the machine is on.
  • Loosen the nuts. Hold the wrench with both hands, place it on the nut and pull the trigger. Do not release the trigger until the nut is loosened. If the work piece has several nuts, loosen each one as we have explained.
  • Tighten the nuts. Make sure the nut is not tight. Place the wrench on the head of the bolt, set the switch to tighten, hold the wrench hard and pull the trigger. Keep on doing this until the nut stops rotating. Do not tighten it too much, as you could damage the nut.
  • Turn the tool off. Once the work is finished, turn your impact wrench off. Unplug the power cord or remove the battery from the base. Store the wrench and accessories in its briefcase.

Cheerful serviceman checking suspension in a car workshop

Modern impact wrenches are very compact.
(Source: Nejron: 9257932/

Shopping Criteria

Impact wrenches are one of the most versatile professional tools. They provide us with maximum torque to tighten or loosen nuts with a minimal amount of effort. Next step in your purchase will be understanding what the decisive factors are to choose the best impact wrench:

Impacts per Minute

The number of strokes or impacts per minute, as well as the speed, must be high enough, since the wrench requires a lot of contact to work on a fastener, both to tighten and loosen. This is important because it will allow you to do very heavy work in a very short time.

For example, if you want an impact gun for unforeseen events with your car, this factor will not be relevant since any wrench is able to loosen tire nuts. However, if you want a machine for professional work, look for one that has a good balance between IMP and the general speed.

Mechanic changing wheel on car

Modern impact wrenches are easy to use.
(Source: Luckybusiness: 47341324/


The power of an impact gun is generally given by the amount of torque, measured in Nm. This is the most important feature and also one of the most underrated.

Having enough power to loosen  anything is key: more torque and more powerful the wrench will be.

Remember that the maximum power must always be greater than the power required for the job. Therefore, it is important to know the value in Nm suggested for the work we plan to perform. For example, for maintenance and repair, we do not require much power, while we do need it to work with machinery.


As we have explained before, a good impact wrench will be one with RPM above 3000. The operation of these tools is based on rotations to tighten or loosen nuts and bolts. More rotations require less effort from the operator, since the impact takes the extra speed of work.

Lower speeds can delay the completion of a task, so if you want to work quickly, this factor will be decisive for your purchase. If this is your case, we recommend you to greatly prioritize speed, even when you have to sacrifice some power along the way.


Traditional impact guns for heavy use on workshops are straight. These are much more expensive and heavy, although they also exert a higher torque than others. These machines have an elongated design, with side and rear handles, ideal to keep stability during the heaviest tasks. They fit in narrow places, but they weigh a lot.

The gun-shaped design is the most common among domestic use impact wrenches. Electric and battery models always have this type of design. They are much more compact and light weighted and easy to transport, allowing you to work much longer. They are turned on with a trigger and are very easy to use for all types of users.


You've probably seen Formula 1 team mechanics run to the pit car and change the four wheels in a few seconds. If you've ever wondered how that is possible, the answer is very simple: impact wrenches that make this task a walk in the park.

In this article, we have reviewed the most important characteristics of impact wrenches. We have explained point by point everything you need to know about them and their operation and we have shown you what the main purchase factors are. Now it's your turn to decide, follow our advice and choose the best impact wrench.

(Source of Featured Image: Vasuta Thitayarak: 55568629/