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Allen Wrench Sizes (Illustrated Charts & Table)

A photo collage of Allen wrench sizes.

Allen wrenches are versatile tools that are designed to work with Allen head screws. These screws are widely used in many applications ranging from new construction projects to assembling modular furniture ordered from your favorite store.

Because there are so many valuable applications for Allen head screws, it follows that there are many Allen wrench designs, sizes, and styles to make working with Allen head screws easier.

Below, let’s take a closer look at the many Allen wrench sizes to understand better which Allen wrench sizes are correct for your next project.

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Allen Wrench Sizes

Long Handle Ball Screwdriver

Long Handle Ball Screwdriver Size Chart

The long handle ball screwdriver is a versatile tool that features a long handle. The head of the screwdriver comes in several common sizes to easily allow you to screw in place an Allen head screw.

The long handle allows you to easily reach into a tight space and help give you added torque that may be needed for stubborn screws.  The ball design makes it super easy to maintain contact with the Allen head screw while you are working.  

Short Handle Ball Screwdriver

Short Handle Ball Screwdriver Size Chart

Comparatively, a short handle ball screwdriver is a similar design and style to the long handle variety, only with a shortened handle. This type of screwdriver can come in handy when working in confined spaces that abut to another space.

The shorter handle will allow you to fit your hand into the assembly, working to screw the Allen head bolts into place.  The ball head design makes it easier to make and maintain contact with the Allen head screw.  

Fold Up Allen Key

Fold Up Allen Key Size Chart

If you are looking for a complete Allen wrench set and want to have options, a fold-up Allen key is a great tool to keep in your arsenal.

This tool is the “Swiss army knife” of the hex wrench family and will allow you to have just about any size Allen key at your disposal. Each small Allen key neatly folds into itself, making this is portable and easy Allen wrench set to tote around.

Long Arm L-Shaped Hex Key

Long Arm L-Shaped Hex Key Size Chart

Simple and to the point, the long arm L-shaped hex key is a steadfast tool for modular furniture. This small and practical tool will make short work of standard Allen head screws.

The tool comes in many sizes, and the long arm will give you added leverage when tightening these screws. This Allen wrench option is commonly packaged with modular furniture because it is easy to make and relatively cheap to produce.

Short Arm L-Shaped Hex Key

Short Arm L-Shaped Hex Key Size Chart

Like the long arm hex key, the short arm L-shaped hex key is a standard for furniture assembly. This tool is very similar to the long arm but has a shorter arm length.

Although the shortened length limits the amount of power and torque you can achieve when tightening hex screws, the shorter arm length is advantageous when reaching into confined and tight spaces.

Loop Handle

Loop Handle Size Chart

Another commonly seen Allen wrench is designed with a loop for the handle. Like other Allen wrench varieties, this wrench comes in a variety of sizes. The looped handle gives you something comfortable to hold on to and can give you added leverage.

The loop is designed to allow you to put a straight and thin tool through the loop, like a long screwdriver, giving you additional power to turn the wrench.  This technique is a great way to increase the turning power of your wrench.

T-Handle Allen Key

T-Handle Allen Key Size Chart

If comfort is your main objective, the T-Handle Allen key is a great way to go. This Allen key variety features a comfortable handle at the top of the wrench.

The handle is ideal for adding power and torque to your hex screws. The T-Handle Allen key comes in several sizes and is available as both a standard or a metric Allen wrench.

SAE to MM Conversions

SAE to MM Conversions Table

Building supplies can come from anywhere in the world, and it is not uncommon to see a mix of standard and metric bolt sizes. It follows that you must easily switch between the two units of measurement to ensure that you always have the right tool for the job. Using a handy conversion chart, you will be able to toggle between standard and metric size easily.

This chart will help you find the right tool for the job every time, ensuring that you are using the correct wrench size or socket.  Although there are many size similarities between metric and standard measurements, it is always best to use the bolt’s true size wrench in question.  

Torx to MM to SAE Conversions

Torx to MM to SAE Conversions Table

The Torx screw head is becoming more common because it is a durable and long-lasting screw design. The head of a Torx screw almost looks like a tiny star.

While this type of screw is becoming more popular, many people have yet to purchase specific Torx socket sets or Torx wrenches. Luckily, it is easy to use a hex socket to work with a Torx screw. The above chart can help you convert a Torx screw diameter to a metric or SAE size hex bolt measurement.

Hex Key Conversions

Hex Key Conversions Table

While using an Allen wrench is certainly practical, many people choose to use a socket attachment to help make short work of hex bolts. A hexagonal socket is a perfect way to screw bolts into place quickly.

The above hex key conversion chart will show you the correct way to measure your hex bolt so that you can find the right hexagonal socket for the screw in question.


Allen wrenches are commonly used in several applications ranging from assembling furniture to keeping your decking boards firmly in place. With so many Allen wrench options and hex key options, it can be downright overwhelming.

Below, let’s take a look at some frequently asked questions to help you figure out which Allen wrench is right for your next project.

What sizes do Allen wrenches come in?

Allen wrenches can be measured in both millimeters or in standard sizes, which uses inches. Small specialty Allen wrenches can be as tiny as 2mm, or sizes larger than 25mm.

What does an Allen wrench look like?

Allen wrenches can take many forms but commonly have a six-sided or hexagonal shape. Allen wrenches can be straight, L-shaped, have a loop on the handle, or fitted with a socket head.

What are Allen key screws called?

Usually, an Allen key screw is called an Allen head screw. Sometimes, you will also see this type of screw referred to as a hex bolt.