How to Match Crochet Hook Size and Yarn Weight

Before you begin any crochet project, you need to get your crochet hook and a ball of yarn. You also need to make sure that your hook and yarn work well with each other. If the hook is too big and the yarn is too thin, you will have a hard time working with them. To get this just right, let’s see how the hook size numbers and yarn weight numbers work together.

Once you enter the world of crochet you are bombarded by all kinds of terminology, abbreviations, and numbers, it’s like a language of its own and that can be overwhelming and intimidating. But here I’m all about using crochet to relax, let go of stress, not get more stressed trying to figure out what’s what in crochet.

The different hook sizes alone can make your head spin, I know! They come sized in letters, numbers, and mm (millimeters, as in metric sizes). Hooks will often be stamped with a letter and the number, like Q/15 and/or mm size of the hook. So, what gives?

Here are how the hook sizes work:

Regular (Yarn) Hooks:

Numbers:

The bigger the number, the bigger/thicker the hook is, so size 15 hook is much bigger than 9 hook size.

Letters:

The further down the alphabet the letter is, the bigger/thicker the hook is, so the size Q hook is much bigger than the size H.

For crochet hooks in US sizes, you will often see the Letter paired with the Number, like this: H-7.

MM:

These sizes are in actual mm, so the bigger the number is, the bigger/thicker the hook is, so a 15 mm hook is a bigger hook size than a 2 mm size.

All these conventions apply to the bigger hooks, like plastic hooks, aluminum hooks, even wooden hooks (like a bamboo hook, for example). These are the hooks you will be working with the most, but they are not the only ones. For finer crochet projects, the ones that work with super fine/thin yarn, there are thread hooks and their sizing is different.

Thread Hooks

There are also thread hooks, they come made of steel, these hooks are so thin they almost look like needles and they are used to work with thinner yarns. These hooks are used to crochet the daintiest, lace-like creations.

Thread hooks also come numbered in mm (and in portions of the mm because of how thin they might get (I’m talking sizes like 0.25mm) and these sizes follow the same logic where the smaller the number the smaller/thinner the hook, but they are also numbered with numbers and those are actually opposite of how the regular hooks are numbered.

With super-thin steel hooks, the larger the number, the thinner the hook, so 12 size hook is actually smaller than 8 size hook. There is no letter numbering for the steel hooks.

The numbers and letters I am talking about are used in the pattern in the US. There is also a UK numbering system that differs from the US one. For that numerical chart, conversion chart, as well as the handy chart for all the US measurements, letters and numbers, head over to the Craft Yarn Council.

Yarn Weight

Now that we have covered the hook sizing and numbering, let’s move on to the yarn weight. Tes, the crochet hook size matters when matching up hook and yarn, but so does the weight of the yarn. You can think of yarn weight as its thickness. Just like the hooks, yarn weight comes described with more than one thing. There are numbers, plies, and names.

Numbers:

The numbering of the different yarn weights is very straightforward. It goes from 0 to 7 and the bigger the number, the thicker the thread.

In yarn, weight 0 would like a sewing thread thickness, and 7 being yarn as thick as your pinky finger. When you look at the paper label that comes with the skein or a ball of yarn, this number will be specified on there, usually as a part of a small picture of a yarn skein.

Ply:

As I mention, there are also ply numbers to describe how thick yarn is, and that’s basically how many thinner strands of yarn make up a thread.

The number of plies can go from 1 to 16 and more. The thinner, lower-numbered yarns have fewer number of plies, so if you grab a yarn size 2 or 3 from the numbered scale, it would match a 5 or 8 ply yarn, and if you pick yarn size 6 which is a pretty chunky yarn, it would have 14 to 16 plys, which makes sense since you need to use more strands to make a thicker yarn.

Weight Names:

And then there are also naming conventions for each yarn weight. Here they are (matched up with the numbers. The thinnest one is Fingering (0), then Sock (1), Sport (2), DK (3), Worsted (4), Chunky (5), Super Bulky (6) and Jumbo (7).

Alright, phew, now that we have learned the language of the hook and yarn sizes, let’s finally get to the point of this post:

How do you match the right hook size with the yarn weight in crochet?

This is actually the easiest part.

First of all, you need to know that there is no hook-yarn matching police that will come if you pair up a really large hook with a really thin yarn (you end up making something super lacy) or a small hook with a really thick yarn (you will end up with something super dense and will probably cuss a lot).

You can match up the hooks and yarns however you want, girl! BUT, to make the work more enjoyable and the results of the pattern looking how you want them too, here are a few tips you can use to match hooks and yarns in crochet.

Find it in the crochet patterns:

First, in any pattern you buy, the designer will usually tell you what yarn weight and hook size they used and recommend. You can always start there. Get the hook size and the yarn weight that the pattern calls for. In the pattern, a gauge swatch is recommended, a small sample that tells you the number of stitches you should have per inch of the crochet fabric. Now, as I mentioned in this post, sometimes your crocheting style might be looser or tighter than the one the designer had (we are all different after all) and in this case, you might decide to use a slightly larger or slightly smaller hook than the one they recommend in the pattern.

Find it on the yarn label:

Second, on the yarn ball or skein itself, there is a yarn label that will tell you what hook size (or a knitting needle size) is recommended for this weight of yarn. That is the recommended hook size you can start with and again, if you find that your crocheting style is looser or tighter than the result you were hoping to achieve, you can try to go down or up a size of the hook to get the tension of the crochet you like.

Eye the match:

And last, when all else fails, just look at the yarn and the hook side by side. You want them to be about the same thickness, with the hook being a bit thicker than the yarn.

Make a sample:

When unsure, always make a small sample of crochet (gauge swatch) using the yarn and the hook you are thinking to use for your project and see how the end result looks like. If the sample comes out larger than you wanted, try to use a smaller hook, if it’s too small, choose a larger hook.

If you are happy about how the sample looks and feels, you can go ahead and pair up that hook size with that yarn weight. I also recommend having a small notebook for your projects where you can write down what yarn weights you like to use with which hook sizes.

And, just to make your life easier, here are handy charts of all the hook sizes (letters, mm) and yarn weights (names and plies) from Craft Yarn Council, a great place for all your crochet and knit standards and references.