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Crochet hook sizes can be a bit confusing, especially if you are either new to crochet or live outside the U.S. and are trying to find the right size to follow an American pattern. I’ll explain the American crochet hook size system, and provide a conversion chart so that you can crochet with ease, no matter where you are!
American Crochet Hook Sizes
American crochet hooks go by two names: a letter and a number. For example, the crochet hook size that is most commonly used for worsted weight yarn is an ‘H’, which is sometimes called a ‘size 8’. From an international point of view, this number is incredibly confusing! Most countries identify crochet hooks by their size in millimeters (mm). A size H crochet hook is 5mm, which as you can notice, doesn’t clearly line up with the number ‘8’. However, this confusing notation isn’t a problem if you reference a conversion chart when you are ready to crochet.
Crochet Hook Conversion Chart
Click here to download my handy printable crochet hook size conversion chart. Not only does it convert between American letter/number sizes and mm – it also lists all the various yarn sizes and the many (many!) names each size can be called.
Use the chart to find the hook size called for by your pattern, and you will be able to identify the size (in mm) that you should use. This should allow you to find the hooks you need to crochet using American patterns, no matter where you are!
The chart also reveals a few other slightly confusing aspects of crochet hook sizes. 😛
You’ll notice that the difference in mm between two hook sizes is not a consistent difference. For example, the difference between a ‘B’ and a ‘C’ crochet hook is .5 mm. However, the difference between an ‘H’ and an ‘I’ crochet hook is 1.0 mm. This can make it difficult to remember all of the conversions, so be sure to check each hook size that you would like to convert. Usually, both the American size and the size in mm are written on the crochet hook package, so that’s a convenient place to check when you’re making a purchase.
Also – the very smallest crochet hooks are called steel crochet hooks and their sizing is different. They don’t include letters, and as the crochet hook gets bigger, the size number gets smaller. It’s weird, I know.
There are occasionally some differences in sizing according to various brands, but the chart includes the most common ones.
These are my favorite crochet hooks, in a set of the most common sizes for worsted weight yarn.
Want to learn more about crochet hooks? This post breaks down the anatomy of a hook and helps you choose which kind is right for you.
Finally – a reminder that all of this is just a guideline! The hook size called for in the pattern, on the yarn band, or in the chart is just a suggested starting place. Crochet a little swatch and adjust your hook size up or down as needed.
Now, you’re ready to start converting and crocheting!
Thank you for this chart.
By chance do you have one for tiny hooks?
Not one for tiny hooks, yet!
Hey there, I am making a beanie with an F hook. The pattern calls for J but it looked whack with a J; so I used the F. With the J hook, I can stop increasing size at sc9, 2sc in one. In your opinion, what does that convert to using my F hook? I was thinking adding 5 more rows, but would appreciate a second opinion.
Changing gauge as it relates to a pattern is a complicated question… unfortunately, there’s no ‘one size fits all’ answer. You’ll have to experiment, do some calculations and see if it’s working for you!
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Hi, I am reading a pattern that calls for a Boye Steel Hook Size 1. I live in Canada and we do not have that brand of hook. Could you please tell me what size hook I would use?
Thank you very much
Hi Gale! Ah, I see… too tiny for my chart! This page says a Boye is 2.75mm!
A 1 is a steel 2.25 mm hook , Adrienne
A steel crochet hook 1.00 mm is a size 12 steel hook. Hope this helps you out.
I have a uk pattern that calls for a No.4.50 (No.7) Aero crochet hook. What is that in a us hook? It also calls for 5 ply crepe yarn. I don’t understand that either. Can you help me?
I’m guessing that’s a 4.5 mm hook? That’s a #7 in US sizes, which falls between a G and H hook in US letter sizes.
I’m a bit confused because I to am Canadian and have been using Boye hooks for years. I even inherited some from my mother so they have been around, in Canada, for 50+ years
Boyes steel hook 1, is a 2.25mm. Boyes has been around, in Canada, for years so the size 1 would be before sizing went metric
its not a 1 its and “I”
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Hi! Your chart has been very helpful. I have a question though. I have a pattern that calls for a C hook (2.75mm) which I don’t have. I do have a steel size 1 hook which is 2.75mm and wanted to know if I could use the steel hook since it’s the same mm? Thank you.
That’s a really interesting question! Although my steel hooks are much smaller than a size C, my gut says that if you have one in the same mm size, then you can use it! I would pop by a store and look at a size C in person, though, just to make sure your size 1 is in the same ballpark.
Yes they are the same size
What are the same size
only one i found i understood, thank you
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I have a Lee Wards size 0. What is that equal to with a susan bates?
Hmm, I’ve never heard of Lee Wards. Do you have reason to believe the sizing is different than Susan Bates?
I was wondering if maybe you could help me, I am about to start working on a table cloth, and the pattern calls for a “Milward Stell Crochet Hook No. 5”. I cannot find a conversion for the Milward to just plain mm, I have seen 1.75 mm and then 0.75 mm. Do you know anything about it?
My guess is that the pattern is referring to a Steel Hook size #5. Those are not included on this chart, but they are sold in stores. I don’t think the brand name is very important.
A 5 in a Milward which is a steel English needle is the same as F in a Susan Bates or a Boye
hi tracy 🙂 am making a shrug, the pattern ask for a n hook but i only have an L hook right now .do you think it would make a big difference on the work if i use a L hook instead of an N hook? thanks a bunch 🙂
Hi Sarahy- I always recommend that you use the hook size that gets you the gauge recommended in the pattern. Otherwise, you may end up with a shrug that doesn’t fit!
I have a pattern asking for a 3mm hook. It’s for a baby sweater, hat and booties. Your chart doesn’t convert 3mm, any suggestions?
I would look online for a 3mm hook- different brands tend to offer different sizes.
Otherwise, be sure you are doing a gauge swatch, you may find you need a different size, anyway!
Hi, your chart is really helpful but i have a small issue i am running into. I bought my crochet hooks online so they were shipped from China and i live in the U.S. and i looked at your conversion chart and back at my hooks and noticed there is a 0.5mm increase between my hook sizes until it gets to 7.0mm then it goes straight to 8.0mm other than that my smallest is a 2.0mm which i don’t think ill use much. But i am trying to make a newborn beanie for my nephew who is due next month and it requires a J hook with the yarn i am using but i am having trouble converting it, and i think it has to do with my hooks coming from China but i am not sure. Can you help???? Any thoughts or help would be appreciated i am clueless right now…
If your yarn called for a size J hook, and yours are marked in mm, then you need a 6mm hook. The increases between sizes aren’t consistent, so don’t worry about that.
I ambos en México and i am wanting to make adult socks it calls for a 4mm G.what is that size in regular crochet needles?
That could also be called a size 6. Did you see the link to the chart?
The issue I’m finding is that different brands of hooks have different size standards for each US letter. A lot of my older hooks don’t have metric sizes stamped on them. That all being said, if you choose your hook and yarn to the pattern’s gauge, you should be OK.
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Why is a 4.0 a G hook on most charts but an F hook in Addi Swings? My British pattern is calling for a 4mm (US G/6) hook. My Addi 4.0mm hook is an F! Should I just typically go by mm sizing? It seems more precise…Thanks!
Yes – go by the mm sizing.
I have susan bates crochet hook
D 3.25 E 3.50 F 3.75 G 4.00
I bought the crochet lite hooks
But the mm is off
D 3.00 E 3.50 F 4.00 G 4.50
So if im using D 3.25 mm
in susan bates can i use
The D 3.00 mm in the crochet lite
When in doubt, always follow the mm size – not the letter.
My pattern calls for a 3 mm crochet hook, but I didn’t see the conversion for that on your chart! Would you please tell me what the conversion is for a 3 mm crochet hook?
3 mm isn’t a standard size and so doesn’t have a letter correlation. You can still get them – they just won’t have a letter on them.
Hi, I am supposed to make a skirt that says to use any sports weight yarn with a US G 4mm.i am planning to use this yarn :https://www.amazon.com/gp/aw/d/B0189VTHKU/ref=cm_cr_arp_mb_bdcrb_top but this says needle recommendation 3.25mm. can I still use a 4mm with this sports weight yarn?..Thank you
You’ll just need to do a test swatch to make sure the gauge is correct – that’s the most important thing when stitching clothing in order to get the fit right.
Bought yarn in Ireland with a 7mm hook. The conversion chart it between a K and L. Not much help. What is it exactly?
It really depends on what you’re using it for. Remember – the size on the label is just a guideline. Are you making a scarf and you want it soft and drapey? Go with the larger hook. Are you making a stuffed animal and you want a tight fabric with smaller holes? Go with the smaller hook.
Can I use a size G5 in place of a G6?
So where is the conversion chart???!!!
Click on the link where it says “Get it here.”
Hi I have got a south maid crochet pattern ( think it might be Canadian ) of Christmas ornaments that’s must be a few years old but I don’t seem to to be able to find a conversation table for cotton and crochet hooks for Great Britain can anyone help me pleased
The part of the single paragraph where it says, “Get it here.”
I have a Susan Bates aluminum hook that states it is a US G6/4mm and a Boye aluminum hook that reads G/6-4.35 mm. The pattern calls for a G hook. Which one should I use?
Crochet a gauge swatch and see which one you like better. The hook size in a pattern is always just a suggested starting place.
I’m using a size 11 English hook to make a tablecloth what is the metric conversion
Most of the time if the hook has a number on it (as opposed to a letter) that number IS the number of mm, so it’s already metric.
I have a pattern that calls for 1/6 mm hook using worsted wt yarn. What size hook do I want to use?
1/6 mm would be awfully small. 6 mm (size J) would be more common for worsted weight. Maybe it’s suggesting a size I (5.55 mm) or J (6 mm)? Use whichever size gets you the specified gauge. Remember that the hook size requirement is always a suggestion. If the finished size is important (like for a garment) you really need to stitch a gauge.
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I started a pattern using a basic Boye aluminum hook size D/3 – 3.25mm. I decided that the hook, because of its size and material, was too flimsy for this project and also hard on my hand, so I decided to go buy a more ergonomic hook of the same size. Problem is, the other 2 hooks I found (joann and hobby lobby) SAY they are size D/3 – 3.25mm, but are noticeably bigger around on the shaft and create larger stitches. Is this normal? Any clue why?
What is the size (letter) equivalent to a 30.00.mm (T30).
I am watching a tutorial on fb for a blanket. The size hook is 7mm. What is that US? Can’t find on the chart
Not every size in mm has a corresponding letter size. Use the sizes around 7 mm to make a guess and then stitch up a swatch to see if you need to adjust larger or smaller.
I have a crochet hook which has two different ends, one is 6/0 and the other is 5/0. What does that mean? What size is it?
I’m guessing 6 mm and 5 mm?
I have a similar issue on one end it say3/0
And on the other it says 4/0
I thought the pattern said q hook is this correct?
Thanks so much!
If I start a project with a 5mm Boye hook. Can I switch in mid project to a 5mm Susan bates hook without it having it be distorted?
It should be fine, unless you’re using the hooks that narrow a bit below the hook. The 5 mm refers to the main shaft and SHOULD be consistent between brands, but (depending on how your crochet) any variation on the narrow area below the hook may affect your gauge.
I am using an H Afghan hook and just realized the pattern calls for a J will I be ok or should I increase/decrease the amount of rows?? ( calls for 202 )
It really depends on what you’re making. If it’s a garment that needs to turn out a certain size, then the recommended hook size is really just a starting point and you need to crochet a gauge swatch to make sure your work is turning out the correct size. If you’re making an afghan or a stuffed animal and size doesn’t really matter, then just keep on with the hook size you’re using – but be aware it may change the amount of yarn needed.
Available in the us, and I’m assuming elsewhere, is a product called a knitting gauge. Many of these knitting gauge tools have holes drilled into them-each hole marked with a millimeter number. If you insert the crochet hook or knitting needle into the holes until you find the smallest hole that it will fit into, that tells you the correct millimeter size. From there, regardless of what brand it is, compare the millimeter size to the chart to know what letter/number combination it is. Hope that helps.
What I can’t figure out is why Boye goes from 3.75mm, skips 4mm, and goes to 4.25mm. I have been searching in vain for that 4.00mm hook for baby yarn; the 4.25 is too large and the 3.75 is really pushing it. I want that happy medium.
I live in the USA and l trying to make a toddler sweater, it calls for a 4mm hook. I have different brands of hooks. I problem is l have a 3.75mm,
4.5 mm. Which one should l use. I am making a sweater for a 2-3;year old
You just need to crochet up a test gauge to see which one gives you the correct size. Remember – the hook size in a pattern is always a suggestion. Even if you have the exact size it calls fo, you still need to stitch up a swatch with the yarn you’re going to use, to make sure the size works out.
I was just wondering if you could make a suggestion to size of crochet hook to use for a crochet pattern that uses a size D\3crochet hook or a size 3.25mm crochet hook because I do not have any of those crochet hooks the only size that I have that is close to it is a 3.0mm crochet hook
sincerely from a person that likes to crochet
You just have to try the different sizes and choose the one that gives you the look and/or gauge you want. The recommended hook size in a pattern is always just a suggestion.
Thank you so much for the conversion chart!
A woman, in 1 of my groups, had a pattern that called for an N3 hook. None of us had heard of That. Have you any information? Thank you.
I have a Bates “US E4/3.50MM” hook and a Boye “Size E U.S.A” hook and the Boye looks thinner?? The “head of the hook” is definitely smaller and the shaft looks smaller to me also but maybe that part is because the shaft is longer than the Boye??
Im about to do a pattern but it says I need a hook of 3.25mm I dont have that…if I used the right hook it would be 11inch top to bottom but how much smaller would it get if say I used a 2.5mm hook instead
You just need to stitch up a swatch to see. The recommended size is always just a starting suggestion anyway – the swatch always gives you the most accurate answer.
This is a great chart! I’m always looking for ways to make my projects smaller, so this is perfect!
Some of the patterns I have been wanting to try call for a J hook that is 6mm. However, my Boye J hook is a 5.75mm according to the measurement on the hook. My local store only sells Boye hooks and none of them are 6mm. Is there a reason this brand doesn’t seem to match the chart?
Love the chart.
Do you think you could do one where it says how many chain stitchs it would take to make one inches I don’t have a ruler and am trying to find something to tell me.
It depends on the thickness of your yarn and how tightly or loosely you stitch. That’s why you need to stitch a gauge for every project – there are so many variables that can effect the number of stitches per inch.