Crochet Hook Conversion Chart and Sizes

Crochet Hook Conversion Chart and Sizes

When making a crochet project, it is very important to use the correct crochet hook size which is why I am so happy to share these crochet hooks size conversion charts with you! Sometimes it can get confusing to determine what size hook you have versus what size you need when looking at US sizes or crochet hooks that are sized in millimeters. This handy chart will help you out so that you will have the answers at your fingertips! 

crochet hook conversion chart

No matter if you have been crocheting for many years, like me, or if you are a crochet beginner, choosing the right hook size is very important and can be confusing at times. 

Below we are going to explore all the different types of crochet hooks and learn about the sizing systems and different types of use. Then, we are going to look at the handy crochet hook size conversion chart we have included for your reference. 

Using this crochet hooks size conversion will help you understand and select the right-sized hook, for your stitching style, and for the project you are making.

Let’s get started with the basics! 

What is a crochet hook size?

The crochet hook size refers to how thick or thin the hook is around. There are different measurement systems used to refer to the size, all of which will be included in the conversion chart below.

What is a Crochet Hook Conversion Chart

A crochet hook conversion chart is a handy tool that will help you look at the different sizing scales and determine which sizes are the same across the scale. 

For example, a crochet hook that is labeled with a letter of the alphabet is measured by the US sizing scale but will have a corresponding millimeter size. 

The conversion chart will help you take the size you have and convert it into different measurement scales so that you know if it matches your pattern’s recommended size or not. 

aluminum crochet hooks

Crochet Hook Size conversion chart – Crochet for beginners

Crochet Hook Definition 

Selecting the correct hook size is important when making a crochet project. The size of the hook you choose, along with the yarn size, will determine the finished size of your project. This is especially important for clothing projects when you are trying to make a specific size to wear. 

Take it from me, early on in my crocheting days I tried to make a crochet vest, and it did not turn out true to size because I used a hook that was too small, and my stitches were much too tight compared to the pattern! 

It can also be important to use the right-sized crochet hook if you are trying to make a certain size blanket, animal, or whatever project you are working on, especially if you want it to be a specific size when you are finished making it. 

Now, before we dive into the sizing of a crochet hook, let’s look at the specifics of what exactly a crochet hook is, and what different parts of a crochet hook are called. 

This information is especially helpful for beginner crocheters, but for those who are advanced, you may still learn a thing or two.

What is a crochet hook?

A crochet hook is a tool you use to make loops of yarn into stitches for crochet projects. The tool gets its name because it is in the shape of a hook. There are several different parts of this hook, each with its name.

crochet hook parts names

Names of Crochet Hook Parts

Hook/Head: The hook’s head is the entire portion of the hook encompassing its whole hook shape. 

Point: The point is the very tip of a crochet hook. On each crochet hook the point does have a pointy shape, but some styles of hooks may be more pronounced than others. 

Throat: The throat is a thinner section of the hook, near the head. 

Lip: The lip on a crochet hook is part of the hook’s head that forms the hook. This is part of the hook that guides the yarn into the correct place. 

Bowl: The bowl of a crochet hook is the portion of the hook, directly underneath the lip.  

Shaft: The shaft of the crochet hook is the section of the hook between the hook’s head and the grip thumb rest. 

Grip: The grip is the flattened section of a crochet hook where your thumb usually comes to rest. This section will also have the hook’s size engraved on some styles of hooks. 

Handle: The handle of a crochet hook, is the remaining bar of the hook, from the grip to the end of the hook. This is generally the portion that you hold on to.

What Are All The Sizes Of Crochet Hooks?

There are a ton of different crochet hook sizes. You can find very large crochet hooks, so large in fact that they are like working with a large wooden dowel, or even the size of your arm. 

Others are teeny tiny! These very small crochet hooks are used for super fine projects called micro crochet and require a special kind of crochet thread to make the small projects. 

Does crochet hook size matter?

You might be wondering if the crochet hook size matters. The answer is, yes, it does matter. When we refer to the size of a crochet hook, we are talking about how big the hook is in diameter. 

The hook size you use is important because you want to pair the right size hook with the right yarn. Most yarn packages will include a suggested size, right on the label. In most cases, thin yarn will require a smaller hook size, and thicker yarn requires a larger sized hook.

Another reason why the crochet hook size matters is for making a specific-sized pattern. This comes into play if you are making a specific-sized item like a blanket, or you are crocheting clothing items.

Specific patterns will tell you how many stitches are needed for different sizes, and to get the size it dictates, the right-sized hook and right-sized yarn are needed to replicate the finished size. 

colored crochet hooks

Yarn Weights

When you are making a crochet project, you will have the option to use many different yarn thicknesses, this is known as the yarn weight. One of the most common types of yarn is worsted-weight yarn. Worsted weight yarn is a lighter yarn, another common weight is medium-weight yarn. These kinds of yarn sit in the middle of the yarn weight spectrum. 

Bulky yarn is another type of yarn weight. It is a thicker kind of yarn and is often used for projects like blankets. For this type of yarn, you are going to want to use a larger-sized crochet hook. 

The other type of yarn is thin yarn, this yarn will be very lightweight. Most baby yarns will be thin yarn, they are much lighter, thinner, and even softer.

Some types of extra-thin yarn can also be known as crochet thread. This is a very thin type of yarn that almost looks like a thread. When making a project with extra thin yarn, smaller hook sizes are recommended.

I always thought you had to find the tiny crochet hooks at a special store, but I just recently found some super small hooks at Hobby Lobby, for a micro crochet project I am working on, and I was so excited! 

Crochet Hook Sizes and Comparison Chart

When it comes to crochet hook sizes, there are many different naming conventions used. The different naming conventions come from different countries, and based on your country of origin, you might be used to a specific naming system found on your crochet hooks. 

The most common naming conventions for crochet hook sizes are US hook sizes and the metric system which names the hooks in millimeter sizes, or mm size. There is also a less common naming convention, the Canadian sizes, which primarily use the UK sizes.

colored ergonomic hooks

Different Sizes

Crochet hooks come in a variety of sizes depending on different systems, the most common ones being the metric system, measured by millimeters, the United States named sizes, and UK sizes. 

The metric system labels crochet hooks in millimeters. On each hook, they are labeled with the number of millimeters across the diameter of the hook. You will see this noted as “a number and” mm hook size engraved on the hook itself.

The mm crochet hook sizes come in a lot of different sizes, all the way from large, to tiny enough that you could probably crochet quilting thread with it if you wanted to. I have done exactly this a few times! 

The various sizes of US hook sizes are also labeled on each hook, but instead of a measurement of how many millimeters across the hook is, the United States uses the alphabet to name each crochet hook size. The smallest size starts with the letter “B”, yes that’s right, there is no letter A crochet hook in US size. They go up to the largest hook labeled “T” which converts to 30mm. 

This might all seem a bit overwhelming trying to figure out what is what, and what size you should use for your project. Or if you are a beginner, it can be challenging to learn which sizes you should start with.

Below, I have included a handy crochet hook conversion chart to help you see the size conversions across the different naming conventions.

Types of Crochet Hooks Included

In these conversion charts, you will notice that there are a few different options. There are two main options that I have included for your convenience. 

  • Regular Crochet Hook Size Chart
  • Steel Crochet Hook Size Chart

These two charts will help you determine the size conversions across these different crochet hook types. 

steel crochet hooks in different sizes

Choosing the Right Size Crochet Hook

When you are looking to choose the right size of crochet hook it will depend on what you prefer to hold, your stitch sizes, the type of yarn you are using, and what you are making. Essentially, it is a matter of preference as to the type of hook you use, but the size of your hook will play a part in determining the finished size of your crochet project. 

Crochet Hook Size Chart 

This simple and handy conversion chart will help you see the different measuring metrics used for crochet hooks across the different brands and different systems.  Check out the crochet hooks size conversion chart below.

Crochet Chart: Crochet Hooks Size Conversion   

Crochet Hooks size conversion chart

Free Download: Crochet Hooks Size Conversion Chart

These crochet hooks size conversion charts are available to you for free in this download. They are a great tool to keep on hand with your crochet supplies and to use as a quick reference when you start a new project. 

To receive your free copy of the crochet hooks size conversion charts, please enter your email address in the box below, and then check your email inbox for your PDF file. 

Please note, that these resources are intended for your personal use only, and not for commercial distribution. 

Different Types of Crochet Hooks 

Not only are there many different sizes of crochet hooks but there are also different types and styles of hooks as well.

The most common types of crochet hooks include steel crochet hooks, ergonomic crochet hooks, aluminum crochet hooks, and plastic hooks. Each of these types can be found in the variety of sizes covered above.

But what are the differences between these hooks? The main difference is in the material these hooks are made from. Let’s look at more detail on each type of crochet hook.

different types of crochet hooks

Types of Crochet Hooks


Steel Crochet Hooks: Steel hooks typically come in very small sizes. These hooks are best used for a crocheting thread or fine yarn. These are the best types to use when making finely detailed projects like crochet doilies.            


Ergonomic Crochet Hooks: Ergonomic hooks usually are made with a plastic hook and a nice rubbery handle that provides an easy grip and more comfort to your hand as you work on your project. These crochet hooks come in many different sizes, especially in the most used sizes. 


Aluminum Crochet Hooks: Aluminum hooks usually come in all sizes. They are typically available for a low cost, and in whatever size you need. These hooks are great for beginners if you are just starting and trying to decide what to buy. 


Plastic Hooks: Plastic crochet hooks also come in most sizes and are available at a low cost. These are not my personal preference as they usually don’t last long and are not very durable.


Wooden Crochet Hooks: Wooden hooks are made from carved wood. Usually, these types of hooks are more commonly available in larger hook sizes.


Tunisian Hook: Tunisian crochet hooks are much longer than other types of crochet hooks. Because they are so long, they are usually used for larger projects where you need more space on the hook. They also sometimes resemble a knitting needle in appearance, only they have a hook on one or both ends.


A knook is a type of hook and needle combination, this needlework tool has a crochet hook-like end, but the other end has a small hole like a needle. This is a very specialized type of yarn tool that could be used for a specialized type of crochet or knitting. 

Size of the Shaft

As mentioned above the shaft of a crochet hook is the rounded section between the crochet hook’s head and the flat grip. The shaft of the crochet hook is very important because the diameter of the shaft of the hook will determine how big the loops are that you crochet. Thicker hooks will make bigger loops and result in larger stitches.

Crochet Hook Styles

There are also different hook styles. While this does not directly determine the size of your stitches, you may discover that you prefer one over the other. The two crochet hook styles are inline and tapered. These styles refer to where the head of the hook is in reference to the hook’s shaft.

teo types of crochet hooks

Inline vs Tapered Crochet Hook Styles

Inline: Inline hooks are ones that have a completely flat head, shaft, and handle. They receive their name because they are all “inline” and don’t have a head that sticks up higher than the shaft.

In comparison to other hooks, inline hooks have a shorter shaft as another characteristic. Some believe that inline hooks help to keep stitches neater, and more even because it is the same size around without any portions sticking up higher than others. 

Tapered: Tapered crochet hooks, on the other hand, are hooks with a more rounded head. They have a lip that sticks up higher than the shaft of the hook, and often have a bigger crochet hook head in general. Another characteristic of these hooks is that they have a longer shaft than inline hooks.  

Most Common Size

Perhaps you are looking to invest in more crochet hooks and wondering what the most common sizes are that you will use. Especially for beginners, knowing what regular crochet hook sizes are will help in your decision making.

The two most common sized crochet hooks would either be a size H or a size I crochet hook

Standard Crochet Hooks By Size

The most common hook size to use with a basic medium worsted weight yarn is a size H hook or 5.00 mm. This is a good mid-sized hook that can work well for most projects.

micro crochet hooks

Smaller Sizes 

Other smaller-sized hooks that are commonly used are G 4.00 mm, and F 3.75 mm. These are both good sizes for slightly thinner yarn. But if you want the smallest hooks, then you are looking at size B in US terms, or super small could be as little as .75 mm or even .60 mm.

Larger Hook Sizes

Although large hooks can be found as big as 30 mm or size T, the most used larger hook sizes include I 5.5 mm, J 6.0 mm, and K 6.5 mm.  

Crochet Gauge Square 

A crochet gauge square is a 4-inch square that is used to measure the number of stitches inside that square. Because each person has their own way of crocheting, some stitch tighter, while others stitch loosely, using a square will help you determine where you fall when making a specific sized pattern. 

To use a crochet gauge square, place the 4-inch square over a block of your stitches, and count how many stitches across are inside of the 4 inches. Then count the number of rows from top to bottom inside of the square. Divide the number of stitches by 4 to determine how many stitches you are creating per inch. 

Ideally, this number should match the yarn label or pattern you are making. If it does not, you may need to adjust the size of the crochet hook you are using.

How Do You Know What Size Crochet Hook To Use?

Recommended Hook Size

To determine the hook size you should be using, it comes down to a few different factors. First, reference the pattern you are making. Does it list a specific sized hook? If yes, then you should try using that size. Most crochet patterns state the recommended size to achieve the finished project size.

Next, you can look at the yarn label. These will often give you a suggested hook size. 

You can also use a gage swatch to determine what your stitches look like and if you happen to stitch larger or smaller than is suggested when using a specific hook size. If you stitch loosely, and the pattern suggests using a larger-sized hook, you may want to consider decreasing the size a little bit so that your stitches per inch match the pattern. 

Finally, the recommended hook size may simply come down to your personal preference. You are, after all making your project. If you want to increase or decrease the hook size used, then, you can make that decision.

crochet hooks in a basket

What if my crochet hook size is not labeled?

You may encounter that the specific size of your crochet hook is not listed on the hook itself. Most hooks now have the size engraved into the hook. However, this hasn’t always been the case. If you were passed heirloom crochet hooks, or found some at an estate sale, that have been around for years, they may not be labeled. 

If this is your experience, there are a few ways you can try to determine its size. The first way is to compare it to other crochet hooks you have. From comparing it, you can probably come up with a good estimate of its size. 

The other way you may be able to determine the size is to find a measuring gauge and measure around the circumference of the shaft of the hook. This will tell you the mm hook size, and some even tell you the letter size. 

The other way you can measure a crochet hook is to use a measuring tape. To do this, take the measuring tape and lay it over the shaft of the hook in question. Then measure the diameter across, not the circumference around. This will tell you the size of your hook in millimeters.

How to Measure a Crochet Hook

To measure a crochet hook, if it is not labeled, you will want to use a measuring tape that has millimeters on it. Then rest your measuring tape across the shaft of your hook, and count the number of millimeters it measures in diameter.

Please note, that this is not a measurement around your crochet hook, only across the top of the surface.

tiny crochet hooks

Importance of Using the Correct Crochet Hook Size

The size of a crochet hook is very important for several different reasons. The hook size you use will depend on the yarn used and ultimately will determine the size of your finished project.

This crochet hooks size conversion chart will help you find the different sizes across hooks when different sizing is used. The best crochet hook for you may depend on your specific stitches, and if you tend to crochet tight or loosely. 

Now that you know all about crochet hooks and their size conversion, it is time to get started on your new project!

Happy Crocheting!

Are you new to crocheting? Make sure to Learn How To Crochet, with this great beginner resource!

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crochet hook conversion chart

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My name is Faith, and I am so glad you are here! I love all things crafts, and have created this site as a way to share my passion with YOU!


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