Crochet Hook Size and Conversion Chart

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Crochet hooks come in a variety of sizes (and styles) to fit the project. If you’re wondering what mm crochet hook size you need, check out this list of crochet hooks by millimeter measurement and U.S. letter sizes.

When I first began crocheting I learned the size of the hook by letter. Maybe because I’m in the United States and we don’t generally use metric sizes. But, actually, the different crochet hook sizes also have a corresponding measurement in millimeters.

Crochet hook needle size is actually managed by the crochet hook manufacturers. So sizing and labeling is done in different ways by different companies. Which is why it’s important to know the size of a crochet hook in both millimeter sizes and the letter size.

White yarn ball with pouch of crochet hooks in different sizes.
Crocheters need a mix of sizes to match the hook to the project.

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Why are there multiple ways to measure crochet hooks?

Maybe you’ve noticed the same letter sizing on hooks of different measurements? I’m looking at you G-6 / 4 mm and G / 4.25 mm! It can be a bit confusing, especially if you’re a new crocheter! I even have one labeled G+!

Crochet hooks with letters and numbers are sizing standards by the different crochet hook companies. That’s why there’s a mix of labeling.

So it’s important to know the corresponding measurement in millimeters. This is the most accurate way to measure crochet hooks.

Crochet hooks in resin, woods and metals displayed in jars.
My collection of Furls ergonomic hooks, which come in resin, wood and metal.

How do you know what size crochet hook to use?

Your pattern will tell you exactly which crochet hook to use. But, you may need to make some adjustments, based on your own personal tension (how tightly/loosely you hold the yarn) to find the best crochet hook for the job.

Of course checking gauge is the best way to make sure your crochet project will turn out right. To check, crochet a gauge swatch, usually 4″ / 10 cm, with the recommended hook size and yarn.

Then compare it to the gauge provided by the pattern to see if yours matches. If it doesn’t then you may need a different hook.

If you have more stitches per 4″ then you will need to try using a larger hook so your stitches will be larger. If you have less stitches per 4″ then you will need to try using a smaller hook so your stitches will be smaller.

Light wood crochet hook on yarn ribbing in beige.
5mm US H-8 crochet hook in camwood from Furls.

The most common crochet hook sizes

The hook you use really depends on what types of patterns/projects you like to crochet. Different hooks and different yarn weights work together to make a variety of fabrics.

Commonly, crochet hook sizes 4mm-6mm are used for #4 medium worsted weight yarn, which is also a popular weight of yarn for many crocheters.

Variety of crochet needles sizes and hooks displayed in mason jars.
A few of my favorite crochet hooks on display.

Hook size affects the size of your crochet stitches

But if you’re an Amigurumi crocheter then those hook sizes, with the same #4 med worsted weight yarn might be 2.25 mm-3.5 mm since this combination will make a tighter knit fabric. Which is exactly what you want with amigurumi.

For example, in my crochet narwhal pattern I use a 3.25 mm crochet hook and #4 yarn for small, tight stitches. Whereas, in my Gia Summer Top crochet pattern I use a 5.5 mm hook and #4 yarn to crochet a fabric that will drape nicely on the body.

So the smaller hooks make smaller stitches, and vice versa. You’ll notice in the chart that the letter sizing ascends from the beginning of the alphabet, as the mm size increases.

Thinner yarns are generally used with smaller hooks. And thicker yarns are matched with a larger size hook.

Your yarn label is a great resource of information and most will recommend a hook size on the label. The crochet pattern is important too, as we’ve seen with the Amigurumi and crochet top examples.

Jumbo purple crochet hook with scissors.
My jumbo 15mm crochet hook, which is lightweight in plastic.

Crochet Hook Size Conversion

  • B / 2.25m
  • C / 2.75mm
  • D / 3.25mm
  • E / 3.5mm
  • F / 3.75mm
  • G – 4 / 4mm
  • G / 4.25mm
  • 7 / 4.5mm
  • H / 5mm
  • I / 5.5mm
  • J / 6mm
  • K / 6.5mm
  • 7 mm
  • L / 8mm
  • M / N / 9mm
  • N / P / 10mm
  • Q / R /15mm

Download the Crochet Hook Size Chart in a PDF here!

This handy dandy downloadable pdf of the crochet hook size conversion chart includes millimeters, US sizing letters, and even the most common yarn weight you would use with that hook!

The size of the shaft, which is the length just past the hook, is used to take the metric measurement. This is what determines your stitches sizes. This is handy to know if you have hooks that are labeled only by letter, but your pattern only gives the millimeter measurement.

This post covers the standard crochet hooks. However there are other types of crochet hooks.

Steel Hooks

It’s important to note that there are also hooks in even smaller sizes. These are steel crochet hooks which are used to work with crochet thread.

The sizing on these hooks is different from regular crochet hooks. The higher the numbers on steel hooks mean a smaller hook measurement.

Tunisian Crochet Hooks

These hooks are measured in the same way, but they have a long handle for holding the stitches.

I hav found the Craft Yarn Council the best source of standards for all things crochet.

A few of my favorite crochet hooks

The Susan Bates hooks and Boye come in a multi pack and are available in most craft stores.

Clover Amour, these crochet hooks have a smooth glide through your stitches. I love the zipper pouch mine came in.

Furls ergonomic hooks. I love both the wood and resin Streamlines and the Odyssey line features smooth gliding metal hooks. The Alpha Series hook is a work of art in itself, as well as being ergonomic.

Which crochet hooks works with which yarns?

The yarn weights listed here are commonly used and by no means, exclusive. If you use a larger hook with a thinner yarn then you’ll have a more open, lacy fabric. And if you use a smaller hook with a larger yarn then you’ll have a denser fabric. It depends on what you want!

  • B/2.25m works with 0-1 weight yarns also known as fingering, sock, baby yarn.
  • C/2.75mm works with 0-1 weight yarns also known as fingering, sock, baby yarn.
  • D/3.25mm works with 2-3 weight yarns also known as sport, baby, dk, light worsted yarn.
  • E/3.5mm works with 2-3 weight yarns also known as sport, baby, dk, light worsted yarn.
  • F/3.75mm works with 3-4 weight yarns also known as dk, light worsted, worsted, afghan, aran yarn.
  • G-4/4mm works with 3-4 weight yarns also known as dk, light worsted, worsted, afghan, aran yarn.
  • G/4.25mm works with 3-4 weight yarns also known as dk, light worsted, worsted, afghan, aran yarn.
  • 7/4.5mm works with 3-4 weight yarns also known as dk, light worsted, worsted, afghan, aran yarn.
  • H/5mm works with 3-4 weight yarns also known as dk, light worsted, worsted, afghan, aran yarn.
  • I/5.5mm works with 3-4 weight yarns also known as dk, light worsted, worsted, afghan, aran yarn.
  • J/6mm works with 4 weight yarn also known as worsted, afghan, aran yarn.
  • K/6.5mm works with 4-5 weight yarns also known as worsted, afghan, aran, bulky, chunky yarn.
  • 7mm works with 4-6 weight yarns also known as worsted, afghan, aran, bulky, chunky, super bulky, roving yarn.
  • L/8mm works with 6 weight yarns also known super bulky, roving yarn.
  • M/N/9mm works with 6 weight yarns also known super bulky, roving yarn.
  • N/P/10mm works with 6 weight yarns also known super bulky, roving yarn.
  • Q/R15mm works with 7 weight yarns also known jumbo, roving yarn.

Types of Crochet Hooks

  1. Aluminum – Boye and Bates are two of the common makers of these types of hooks. Most of us start out with a basic set of aluminum hooks. These are a wonderful and cost effective way to get many of the sizes you will need to start crocheting.
  2. Plastic – These are lightweight and affordable. This is also a great option for those starting out.
  3. Wood- Many kinds of wood are used to create hooks. Bamboo is a lightweight wood that’s popular for hooks in both the standard and ergonomic category.
  4. Steel – These hooks are the smallest and used for crochet thread. They have a separate numbering/measurement system.
  5. Ergonomic – For those who crochet often, or for long periods, an ergonomic hook can keep your hands from hurting. These usually have a larger handle that fits nicely into the hand.
  6. Tunisian Hooks – These are made for Tunisian crochet and have a long handle for holding the stitches, much like a knitting needle.

There is so much to learn when you are learning a new craft! Take it slow and get the basics down. There will be opportunities to keep learning and growing in your crochet art.

What crochet projects can I make with a…

Katerina kitty crochet lovey pattern is an example that uses a small 3.25 mm hook for the cat parts and a 5.5 mm hook for her dress.

The toddler sun hat crochet pattern is a popular one that uses a 4 mm crochet hook.

5mm crochet hooks are very popular in crochet patterns, here is my most popular crochet shawl pattern.

For those who love sweaters the Sunset Sweater crochet pattern uses a 6 mm crochet hook and #4 weight yarn.

For those who have chunky #5 yarn and a 7mm hook the Ana Hat is a chunky, slouchy hat crochet pattern.

Ready to take on crochet color work? The Tuscan Charm cowl pattern uses #5 yarn and an 8 mm crochet hook.

If you have a 15mm hook and some jumbo yarn, you might like this chevron blanket crochet pattern that features striped #7 yarn.

The Sheila Cowl crochet pattern makes a great gift with a 10mm hook and one skein of #6 super bulky yarn.

Of course there are so many great hook and yarn combinations, these are just a few!

If you love learning by video tutorial be sure to check out my YouTube Channel!

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