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Crochet Hook Sizes & Conversion Chart

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No bones about it, crochet hook sizes are confusing. Should you follow the letter, the number, or the millimeter when selecting a crochet hook for your next project? This article, including a handy crochet hook conversion chart, will help!

crochet hook sizes conversion chart

Crochet Hook Sizes & Conversion Chart

There are several different ways in which hook sizes can be labeled. With so many variations, crocheters are bound to get confused at some point along the journey. Which sizing method is tried and true? First let’s discuss all of the ways crochet hooks are categorized and sized.

bright crochet hook set

The Bright Crochet hook set from WeCrochet.

radiant wood crochet hook set

The Radiant Wood Set from WeCrochet.

Crochet hooks can be made using a variety of materials including wood, aluminum, plastic, and bamboo, among others. The majority of hooks range from 5″ in length (such as the Clover Soft Touch) to 6″ (such as Susan Bates, Radiant, and Boye), to 7″ (such as the Furls Streamline Swirl).

Boye crochet hooks

Susan Bates crochet hooks

Different hook manufacturers label their hook sizes using different methods. Some hook brands use the American letter system, some use the American number system (which is not the same as the metric number), some use both of these, and then others only use the actual width of the shaft in millimeters. Because it is up to each individual crochet hook manufacturer to label their hooks, the best way to determine hook size is to go by the actual measurement: that is, the size in millimeters. This is quite literally the width of the shaft of the crochet hook.

sizes of crochet hooks

The American system of labeling crochet hooks uses the alphabet. Starting with a B (2.25mm) and ranging up to an S (19mm), although M/N is typically as large as you’ll need in your arsenal.

The UK method of sizing crochet hooks uses numbers. The smaller the number, the larger the hook. Confusing? I know.

how to find size of a crochet hook

Because of how muddy these waters can be, there is one characteristic that ALL crochet hook sizes have: the actual measurement of the shaft. If the size in millimeters is not listed on your hook, a hook gauge is an excellent tool to have in your crochet kit. Note that there are gauge tools for both knitting and crochet – and they are not necessarily interchangeable.

In order to correctly check the size of crochet hooks you want to get the kind that has a slot into which you rest the hook, NOT a hole that you put the hook through (like this one).

Great examples of crochet hook gauge tools can be found here, here, and here.

crochet hook size gauge tool

The holes are better used for knitting needles, since the head of the crochet hook can be funkily shaped depending on the brand and may not give an accurate reading. The hook shaft should fit perfectly when slid into the corresponding slot.

The bottom line is that the best means of selecting a hook size will always be to go off of the millimeter itself. For example, the diameter of a 6mm crochet hook (also known as a size J/10 in American terms or size 4 in UK terms) is just that: 6 millimeters. It doesn’t matter which brand, where it was produced, how long the hook itself is. If the width of the hook is 6mm, it is universally known as a 6mm hook.

The Furls Streamline Swirl G+, 4.5mm hook.

To further add to the confusion, not all hook sizes have the equivalent depending on which terms you use. For example, a size 4.5mm hook has no real American letter size (although some call it a G+), and is commonly referred to as a size 7 in both the US and the UK. Not to be confused with a 7mm hook, which does not have an American letter OR a UK number. Oy!

The Clover Amour hooks are my favorite for “larger” hook sizes and range from 6.5mm to 15mm.

Save this handy Crochet Hook Size Conversion Chart for future reference.

Crochet hook size conversion chart

One last note about crochet hook sizes. You may have seen some tiny, tiny hooks. Those are used for making doilies etc, and are a whole different ballgame. Those steel hooks are for crocheting with crochet thread… but going by millimeter will always your best bet there as well.

Have questions? Feel free to ask in the Heart Hook Home Crochet Community where there are over 65,000 other friendly crocheters! Happy crocheting!

Crochet Hook Size Conversion chart

More for you:

Understanding Crochet Gauge and How to Measure It

Why Size Matters in Crocheting and Knitting

Tunisian Crochet Hooks Guide

How to Make Stitch Markers and Hook Reminders

Felted Crochet Hook Case Crochet Pattern

28 Yarn Box Subscription Services for Knitters and Crocheters

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15 Comments

  1. UK have been on the metric system for 50+ years so there are no more “UK” sizes although I expect there are some old hooks/needles lying around.
  2. The pattern I am using calls for a 4.25mm crochet hook. I only Have a 4.0mm and a 4.5mm. Which should I use? I am Making a round coaster.
    1. Hi Trudy! Which set of hooks were you referring to? I have several pictured...lol. The hook gauge can be found here: https://shareasale.com/r.cfm?b=726901&u=780171&m=59159&urllink=www%2Ecrochet%2Ecom%2Fswatch%2Druler%2Dand%2Dneedle%2Dgauge%2Fp%2F84093&afftrack=
  3. I was needing to know if I could use a 3.5 crocheting book steel in place of a 3.25 because that is what my pattern calls for. Thank you.
  4. I need the conversion chart for needle sizes sent to my email address so That I can print it off for future reference. Thank you so much for all of your assistance.
  5. Where did you get the elephant crochet hook gauge tool? I have looked on all 3 that put but can not find it. Please and thank you.
    1. Hi Dorothy! It is made by Knitters Pride and I think Jimmy Beans Wool has some available for purchase.
  6. of course i've just gotta ask where did you get the kewl purple elephant gauge in the picture?? TY for the info. & hook conversion chart - I just joined or at least submitted my request to join ur FB group too :)
  7. great chart I am thankful... I recently have been running to google for answers... now I have my own copy
  8. Wow! You have explained this very confusing state of affairs so clearly. Thank you. I love being in this wonderful Crochet Community.
  9. Wow! Ashlea, this is such great information and so clearly defined. I’m so glad I’m part of your crochet world!!!