Why Does Crochet Hook Size Matters? What if I Use a Different Hook?

The crochet hook is one of the two basic tools you need to crochet. Yarn and a hook. Technically, you can get buy with just those two things. So let’s talk about those hooks. There are so many different sizes, and they are measured in PARTS of a millimeter. That is such a small difference! Why does it matter if I use a 5.5 or 6.0 mm hook?

Crochet patterns specify what hook to use so you end up with a project that is the same size as the original design. If you use a larger hook, your project will be bigger with looser stitches. If you use a smaller hook, your project will be smaller with tighter stitches.

If you want to end up with a project that is the same as the original design, in general, you want to use the same size of crochet hook. But…..as there always are with rules, there are exceptions to this! I will dive deeper into the answer to why the crochet hook size matters and what happens when you change it!

Why Crochet Hook Size Matters

Typically when crocheting you want the final project to be similar, if not identical to the one you see in your pattern. To achieve this, all of your stitches have to be the same height and width as the original designer of the pattern.

There are multiple things that affect this, the easiest to control are the yarn you choose to crochet with, and the hook you use to manipulate that yarn. Picking the right “weight” of yarn usually isn’t a problem. People tend to buy the yarn to match the pattern. But the hook could be a different story.

We don’t typically buy a new hook for every project, right? We have our set of hooks at home and continue to use them forever (or until they bend or break or you just want a different design). So what if you get home from the craft store and find that you don’t have the size of hook called for. Maybe you lost one of the multi-pack you purchased just didn’t include that size.

You think, “That’s okay, I have one that is close enough. It is only 0.5 or 1 mm different. I’ll just use that.”

Well, this may work out just fine, but in general, you are putting your work in danger of being the wrong size at the end!

The other main reason that the hook size matters is yarn usage. Even if you don’t care about the end size of the project, which maybe you don’t for a blanket or something, you need to think about the amount of yarn you purchased.

Using a larger crochet hook to make something with the same number of stitches uses more yarn. I will get into this in more detail later, but if you have a limited supply of your yarn choice, you will not want to use a larger hook and end up with a larger project.

When Does Crochet Hook Size Matters

Technically, changing crochet hook size matters all the time because it changes the outcome of your project. But in reality, some things that you crochet are not as important to have the “right” size or “right” tension (amount of space between and within your stitches).

So what are the main scenarios in which the hook size will matter?

When finished size matters

One time that it is extremely important is when you are crocheting clothing. You have a pattern that gives you the dimensions of a shirt or dress you are making, and you chose the one that will fit you. You choose a hook that is 1 mm smaller than called for, and you end up with something the size you wore in middle school instead of the size you are now! Well, time to frog it (rip it out) and start over!

Another project where it is important is for hats. You need the hat to fit on the head of the person it is for. So, for that little newborn hat that you made with a hook only a 0.5 size larger than called for, you could end up with a hat for a 1-year-old.

When tightness of the stitches matters

Here is one you may not have thought of that comes down to the airiness in the pattern, not the size. Potholders! You definitely do not want your pot holder to have more air space, you will end up with burnt hands!

Similarly, for a blanket, you may not want to use the larger hook because you would end up with an “airier,” looser blanket that may not be as warm. Depends on what your priorities are though.

When you have a limited supply of yarn

I have to mention again, that a time when the hook size matters, even when the project size doesn’t really, is when you have a limited amount of the yarn you need. This could happen for a variety of reasons.

You may have purchased the yarn at a thrift store (side note-GREAT place to find inexpensive, but sometimes awesome quality, yarn!). Well, that store probably doesn’t have anymore and that yarn is likely out of circulation.

Or maybe you bought the “correct” amount of yarn at the craft store all from the same dye lot so it is exactly the same color without variations. Well, now 3 weeks later they don’t have that same dye lot and the color is slightly, but noticeably different. It could also be out of circulation, just like the thrift store yarn, if you are like a lot of us and procrastinate starting or take 2 years to finish that complicated pattern.

For more information on how hook size affects the amount of yarn used, check out my other post about this specifically!

How Much Does Crochet Hook Size Affect The Size of the Project

I will provide a somewhat extreme example, then a more realistic one.

Let’s say you are making a blanket. The pattern calls for a size 5.5 mm (I) hook. You decide to go crazy and use a size 10 mm (N) hook. (I understand that the only reason you would do this is to purposely get a MUCH looser blanket. This is not an “I don’t have that hook size, let me go up one,” type of situation.)

Well, the final project, based on a swatch that I crocheted and calculated for, would be significantly larger. In fact, the change from size I to size N hook actually results in a project about 40% larger! Makes sense, right? The hook size is approximately 40% larger. You would also use about 17% more yarn with the larger, size 10 mm (N) hook, over the smaller, size 5.5 (I) hook.

Okay, let’s be more realistic. Let’s say the pattern calls for the size 5.5 mm (I) hook, and you don’t have that one. You go up to the 6.0 MM (H) hook.

The final project, based on a swatch that I crocheted and calculated for, would be about 10 % larger when using the 6.0 mm (H) hook versus the called for 5.5 mm (I) hook. Again, makes sense because the hook is about 10% larger. You would also use about 8% more yarn with the larger, size 6.0 mm (H) hook, over the smaller, size 5.5 (I) hook.

What Besides Crochet Hook Size Affects The Size of the Project

Yarn weight

The yarn weight will affect the project size even if you use the same size of hook called for in the pattern.

Say you have a size 3 (light) weight yarn that you want to use, but the pattern calls for a size 4 (worsted) weight yarn. You will have a smaller end result. (In this case, you may actually go up a hook size or two to compensate.)

The opposite is also true. A size 5 (bulky) weight yarn would result in a larger project than the called for size 4 yarn.


This is something that is individual to each crocheter. We all hold our hook and yarn slightly differently and have a slightly different technique to actually creating our stitches. This actually results in differences in the tension of each of our stitches.

Some crocheters naturally have tight, small stitches, and some have large, loopy stitches. This will affect the finished size of the project.

If you are an experienced crocheter, you may already know that you typically have to go up or down a hook size to achieve the correct result.

Familiarity with the stitch

When a stitch is new, we work it differently than when we are familiar with it. That is just a fact of life for everything. We are never as consistent or as proficient with a new task or technique. You will start out clunky then get better at it. This WILL affect your tension.

Accurate stitch counting

This may seem obvious, but it can be really challenging at times, especially for things where you are constantly increasing or decreasing the number of stitches in a row or a round. If you are like me, sometimes you get distracted and end up having to frog a few rows to fix where you dropped a stitch.

How To Ensure You Crochet to the Right Size (or at Least Improve the Odds)

Choose the right hook

I think I covered this above pretty well. The only caveat to it that I have to add is the “right” hook may NOT actually be the one listed in the pattern. Keep reading to get to the gauge swatch to get more details.

Choose the right yarn

In general, stick with using the yarn weight that is listed in the pattern. This will get you really close to the same. If you can and want to, use EXACTLY the yarn that is listed in the pattern. This will ensure the yarn is the same size!

Different brands, and even different lines within the same brand, could have a slightly different thickness even though they have the same yarn weight listed. Sometimes you can even feel the difference if you are comparing side-by-side or switching brands in the same project (not recommended).

Again, you will need to take another step to ensure that your yarn works up to the same size as the pattern. Keep reading to get to the gauge swatch to get more details.

Practice any novel stitches

Usually, when learning a new stitch, you start tighter. This is because there is a certain level of “stress” associated with starting something new. Your muscles don’t know what to do, so they just try anything and everything to get it right. (This is true in my patients in physical therapy as well!) As you practice that “stress” decreases and you can be looser and more relaxed with your movements.

Practice your novel stitches by just doing a small swatch of them until you are comfortable with the technique.

Make sure you count

We all get distracted sometimes. We may not read the pattern just right, or we may just inadvertently skip a stitch. Either way, you will address this by counting. You may not count every single row (though it is recommended), but don’t go too many rows without counting. Then you risk having to frog a lot of work and start again, wasting time, energy, and motivation.

Do the gauge swatch!

As you probably guessed by my references to this section, this is the most important step to making sure that you have the correct size at the end of your crochet project!

Pretty much every pattern provided a gauge. It will usually read something like, “13 stitches and 13 rows in 4″ square in single crochet”. Basically, it means you are supposed to crochet that many stitches and rows, then measure and make sure it is that size.

If you end up with a larger square, you will want to adjust something. The easiest thing to adjust is the hook size. In this case, you would go down a size or two and do the swatch again to check your gauge. If you end up with a smaller square, do the opposite.

You could just try to crochet “tighter” or “looser”, but I definitely DO NOT recommend this because you will generally gradually default to your original, natural tension. Then you would end up with, not only the wrong size, but a lopsided, shrink or growing, project!

When it May Not Matter if You Use the “Right” Crochet Hook

If you are looking for a project that is a certain size at the end, and don’t really care about your project having more air space/larger holes, you can choose to use a larger hook.

Maybe that throw blanket or that scarf that you don’t need to be too warm. Maybe a shawl. Some decorative type crochet work like Christmas tree ornaments may not look too wonky if there is more air space, especially something like a snowflake. (If you are looking for the same size, you will need to alter the number of stitches in the pattern).

Alternatively, if you are following a pattern and don’t care that your project comes out smaller or larger than described. In this case, you can use a larger or a smaller hook.

Maybe a toddler blanket that is just for dragging around. Or again, those Christmas ornaments.

Some examples of projects where you might not care TOO much about EITHER finished size or airiness are shawls, throw blankets, face scrubbies, doilies, embellishments like flowers or hearts or bows, washcloths, and decorations like Christmas ornaments or standing trees. I’m sure there are many others, but this is a small list of ideas for you.

Isn’t it amazing how much there is to think about with a simple crochet hook! Who knew that a half of a millimeter could matter! If you think of any other questions about it, drop me a comment, and I will answer the best I can!

Now it is time for YOU to get Crafty with Ashy! For my own inspiration, show me YOUR recent projects in the comments!

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Hi! I’m Ashy. I am a Christian, wife, mom, and physical therapist. I am also an amateur painter, baker, crocheter, and miscellaneous crafter. I hope to be able to share some of my enthusiasm for creating with you and to inspire YOU to begin, continue, or grow YOUR creative outlet!

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