How to choose yarn for knitting

A handy little masterclass showing you the best yarn for every project. How to choose color combinations, yarn weight, and materials the right way.

So, you want to knit a scarf, a sweater, or some socks. And now you are wondering what’s the best wool for that kind of project? How do you choose yarn for knitting without regrets? Well, then you came to the right place because in this tutorial I will show the art of yarn picking and substitution step-by-step.

I keep on telling my students that finding the right kind of yarn is 80 percent of job. The best pattern can look awful with the most expensive yarn ever and the simplest scarf in garter stitch can still look stunning if you choose the right yarn. That’s why I prepared a little questionnaire for you with 5 important yarn properties you need to be aware of before you click on “buy now”.

Important note: Most of what I say will be from the perspective of starting a project from scratch. But the same principles and considerations will matter when you try to substitute yarn for a pattern. Then, you absolutely want to make sure that the alternative you pick ticks off all these boxes and behaves in a similar way compared to the original yarn.

Reading tip: The best knitting yarn for beginners

Step 1: Decide on a material/fiber

Before we can even talk about yarn color combinations and needle sizes, you have to think about the material you need for your project. Most laypeople may believe that wool and yarn are interchangeable terms but that assumption couldn’t be further from the truth. Even experienced knitters will often pick the color first and then worry about the rest. A huge mistake, if you ask me.

There are three basic kinds of materials available to modern knitters:

1. Protein-based fibers obtained from shearing animals. They are typically very warm, very soft, breathable, and quite stretchy. On the negative side, they can also pill and felt, and are not machine washable. Common examples: Sheep wool, alpaca, yak, mohair, angora, cashmere, camel, qiviut, slik.
2. Plant-based fibers harvested or extracted from plants. They are usually not very warm, can absorb a lot of water, some of them have an excellent stitch definition, and they are often machine washable. They are not very stretchy and can be more difficult to knit with. Examples: Cotton, linen, nettle, bamboo.
3. Synthetic, purely man-made fibers. Often very inexpensive, quite soft, and quite versatile. But not breathable at all, and often not the highest comfort factor. Examples: Nylon, Acrylic, Polyamid.

Factor #1: How sturdy and durable should my yarn be?

Hand knitting takes time and you don’t want your garment to fall apart after the first wear. So, at the very start, you need to deliberate what kind of wear and tear your project is going to be exposed. Socks or sweaters are very popular items to knit but you and your knitting will go through a lot together, and not every material/fiber is equally durable.

For example: Pure sheep wool felts when it gets warm. Cashmere pills a lot and doesn’t have a very high tensile strength. Mohair sheds like crazy, and nylon are pretty much resistant to everything baring intense heat/fire but cannot absorb any water. That’s why most people knit socks with a nylon/sheep wool blend to get the best out of both worlds: breathability, softness, and durability.

Not every project needs a durable yarn. If you are knitting something like home decor or a light shawl, then it really doesn’t matter. A simple hat, a scarf, or a shawl doesn’t exactly need army-grade acrylic yarn either. Here you can go for much finer qualities and more delicate yarn.

Important tip: You should always consider knitting with two strands held together. That way you can blend two desired characteristics into one. E.g. you use sturdy sock yarn as a base and add a fluffy mohair thread for that special something. Or, you go for a blend straight away.

Factor #2: Warmth, breathability, and water absorption

A lot of knitwear is designed to keep you warm in winter. But not all fibers are equally warm. Typically speaking, the softer fiber, the warmer it is. That’s because the thinner the individual hairs are, the more tiny little insulating air-pockets are created. This can be a pro and a con.

Qiviut is, arguably, one of the softest (and most expensive) fibers in the world. But it’s also so warm that you probably couldn’t wear a sweater made out of this precious fiber obtained from the muskox in a worsted weight quality. And even sheep wool, when knitted into a sweater using a chunky yarn, can quickly become unbearably hot.

A light t-shirt knitted out of silk or linen yarn can, however, be perfectly suitable for a cooler evening in summer.

Here’s a word of warning: Very often you find adages like alpaca yarn or camel yarn had a cooling effect and were thus acceptable for summer garments. There’s no scientific proof for these effects. Often this advice is built on poorly understood research (in this case it’s based on the belief that the individual hairs are hollow and transport heat away. However, only the coarse hairs are hollow and those are never used to spin knitting yarn; source).

Most artificial yarns, acrylic, nylon (etc.), can be very soft as well but they often lack breathability. Meaning, a sweater can very quickly feel like a sauna. On top of that, they cannot absorb a lot of water (unlike sheep wool or most other fibers obtained from animals), so they are probably not the ideal choice for a coaster or a towel. Cotton, on the other hand, excels in that area.

Factor #3: How stretchy does my yarn need to be?

The third question you might want to ask is how stretchy your fabric needs to be. Sheep wool, for example, is quite stretchy. Something you might have noticed when washing your favorite sweater. It always contracts a bit before it loosens up again. But you will also notice this on the needles/when you are knitting. The thread always bounces a bit back and that makes it quite easy to knit with.

Cotton, linen, and most other plant-based fibers, on the other hand, are very unresponsive to stress. So, as long as you don’t wash them, they pretty much stay the way they are. That’s why many say these fibers are not very suitable for beginners. They are much harder to knit with.

Again, this can be a pro and a con. Alpaca yarn, for example, is notorious for stretching out after the first wash and when the whole weight of a sweater rests on the shoulders seems. Mostly this has to do with the lack of crimp (meaning how curly the individual fibers are) and the way it is spun. Especially for fitted garments (as opposed to a scarf or a shawl) you want a fiber that doesn’t drastically change its length under stress or after washing.

Reading tip: How to knit a swatch and get gauge the right way

Factor #4: Soft? Fuzzy? Lustre?

The next question, when it comes to choosing yarn for knitting, has to do with the overall appearance of the fiber. Cashmere is known for its beautiful halo – the fiber typically blooms after the first wash. Cotton, on the other hand often has a beautiful smooth luster, while sheep wool can exhibit both depending on the spinning technique.

Why does this matter? Well, when you are knitting intricate cables or bavarian twisted stitches, you probably don’t want to do it with a mohair yarn that blooms so much you won’t be able to see anything of your hard work. Knit a pattern in plain stockinette stitch using the same yarn, and that fuzzy softness can add the little something extra to turn a boring pattern into something that spells interesting perfection.

Note: The same obviously applies to busy yarns with speckles, bobbles, etc from indie yarn dyers. I will speak about color further down below.

Factor #5: Machine-washable or handwash only?

And last, but certainly not least, you have to think practically. While I personally don’t mind handwashing all that much, a mother or father with 3 kids probably doesn’t want to handwash the hand-knit sweaters of their little ones every time they get dirty. And some items, such as dishcloths, towels, or even socks need to see higher temperatures when washing, simply because that’s the only way to get them clean (and kill bacteria, etc).

As a rule of thumb: Most untreated protein-based fibers are not suitable for machine washing. They will felt when they are exposed to heat and friction under the influence of water. Look out for superwash yarns that have been chemically treated to prevent felting.

A good yarn label should have all the information you need to make this decision. I have a full post on how to read yarn labels and how to make sense of all the symbols you might want to check out.

Step 2: Find the right yarn weight

After you decided on a fiber, you have to choose the right yarn weight. This is typically a pretty straightforward process and there are only a couple of things to consider:

1. The heavier your yarn (i.e. the thicker the thread), the faster you will be able to finish it as you will need fewer stitches to create the same length of fabric. After all, a smaller stitch will typically take just as much time as a stitch knitted with a much chunkier yarn.
2. Using a chunky yarn also means more warmth. Depending on your individual temperature perception and the intended us, picking a lighter or thicker yarn can be recommended.
3. The thinner your yarn, the more drape your fabric will have.
4. Knitting with a thinner yarn will also result in a more delicate finished project while using chunky yarns can be very striking.
5. The chunkier your yarn, the more yarn (not in yards but in weight) you will need to finish an object. This can be an important price factor.

For example, you can knit a hat in fingering weight yarn or DK weight yarn. You might need only 8 hours to finish the DK weight hat, while you will need twice as many hours for the same hat using your average fingering yarn. If you go for a 1×1 rib stitch, the DK hat will have a lot more structure and will be less slouchy than the equivalent using a lighter yarn.

If you got for lacier patterns or colorwork (like intarsia), it also means that you have maybe 30 percent fewer stitches on your needles you can use to develop a pattern. Think of it as pixels on a screen or graph paper. The lower the resolution on your TV or screen, the less detail you will be able to see. On top of that, you will typically also need 30 percent more yarn in weight, making the DK weight hat often a bit more expensive (as you need two skeins instead of one and a half).

Step 3: Understanding ply and why it matters

The next step is finding the right kind of thread. Sadly, spinning is not very popular among modern-day knitters anymore. I do have to admit, I don’t spin my own yarn either. Still, even if you don’t, it’s very important to understand some basic plying- and spinning theory. There are three main concepts every knitter should be aware of:

A) Woolen spun vs worsted spun

Before yarn can be spun, it needs to be prepared for drafting. The raw fiber can either be carded or combed. Without going too deeply into the industrial spinning process here, this distinction matters a lot.

These days, most commercially available yarn is worsted spun. This means the spinner went to great lengths to align all the different little hairs that compromise each little thread as parallel as possible through combing. Some knitters may be familiar with roving. That’s the result of that process. And yarn that is spun from such rovings will be much smoother, have more drape, an excellent stitch definition, and will be much more resilient.

Woolen spun yarn, on the other hand, is only blended before the spinning process using a simple carder. Under magnification, the individual hairs are all sticking out this way and that way. This will create a very lofty thread perfect for warm garments. The resulting yarn will typically bloom beautifully after washing, making it excellent for colorwork, but it might eventually pill. Also, the stitch definition is typically less ideal as the yarn has more twist stored in it making individual stitches roll out in different directions.

How can you tell them apart? Typically you can tell a woolen-spun yarn at a glance. It’s much loftier, often very fuzzy, and not very smooth. When you pick the individual plies apart, the difference will often be even more noticeable as the individual plies won’t form a very uniform line and you might even see little fluffs peeking out here and through. Worsted spun will be very uniform, often with a nice sheen to it. Of course, you have to take the general appearance of the fiber into account.

b) Single ply, 2-ply, 4-ply, and 8-ply

Another very important factor is the ply. This means, how many individual strands were used to form the thread. If you ever created your own cord or unwound a hank of yarn, then that’s the exact same process. By twisting many small strands into a bigger thread, you add durability.

Think of it like this: Stack two hairs on top of each other. You will easily be able to pull them apart. Nothing glues them together after all. Twist the same two hairs around each other. Then you will still be able to pull them apart but it will take more of an effort. Next, twist another two hairs together and then twist the two twisted strands together one more time. The resulting “4-ply thread” will be much more durable.

Typically, the higher the ply, the more durable a yarn will be and the less likely it will pill or bloom. But it also means there is more twist stored in the thread. While spinners will try to create a balanced thread as much as possible, some of the twist will still transfer to your knitting (especially as you tend to add or subtract twist as you wind a ball or knit).

And often this will be visible in your final project – something every knitter might have experienced when knitting stockinette stitch with a highly twisted 8-ply yarn. Suddenly, you don’t see the Vs neatly stacked upon each other anymore but more a continuous line that almost looks like a different stitch pattern. That’s because the individual loops sort of want to unwind/untwist to balance themselves out – much like a snake captured in a bunch of snake charmer’s basket.

Now, this topic definitely deserves its own article. Your main takeaway here is that the ply will influence the way the final stitch will look in your fabric. It can roll out, roll in, stay put, or twist in every direction. Especially for lace or cable projects, this will be very important as a certain stitch definition is essential for the success of the fabric.

And often, the only way to find out how a particular yarn behaves is knitting a swatch and comparing it to other yarns. As no spinner and no knitter is truly alike. The way a yarn was plied together (S or Z-spin) can also influence the overall appearance. These days, most commercially available yarns show an S-spin. The distinction may only be important for single-ply yarns (which are typically a Z-spin), but they typically behave in a very peculiar way anyway.

Step 4: How to choose yarn color combinations

Most knitters I know struggle with choosing color combinations. And indeed, when you enter your local yarn shop with racks upon racks filled with beautiful yarn, which one should you pick? All are beautiful but which ones work well together? The answer is remarkably easy: Learn about color theory.

Or actually, it is even easier in these days. Starting with Isaac Newton, countless books have been written about color theory and it’s certainly a remarkably interesting subject. But the truth is, these days there are simple apps and websites that do the job for you. I am typically using Canva and I feel it’s very accessible to non-web designers but if you google the term “color wheel” you will find many similar apps and websites.

These are programs with web designers in mind, but that doesn’t mean you cannot use them as a knitter. Simply use the color picker and see what it spits out. Typically, complementary colors are what you are looking for. Add white, black, or grey as a background, and you are set.

You can also go for triadic colors for a much more dramatic effect. When applied to knitting, it helps to pick subdued shades, use one neutral background color, and limit yourself to using one of the three colors only as an accent. The 60-30-10 rule is quite popular.

E.g. you decide on knitting a yoked Fair Isle sweater using a creamy off-white tone as a base. And for the yoke, you use a red tone as your main color, a blue tone as an auxiliary tone, with tiny speckles of green as a contrast. To tone things even further down, you could go for plant-based dyes.

Step 5: How to choose the right needle size

Once you settled on a fiber or blend, you still have to find out the right needle size. And the only way to do this is by knitting a swatch. Why is this so important? First of all, knitting a swatch will tell you if all the assumptions you made so far are right. There are so many little factors playing together and even with the most careful planning, things can go awry. Also, it will help you to get gauge for a pattern.

And that’s probably the most important step when we are talking about yarn substitution. Even if your pattern uses a dk weight worsted spun yak yarn, and you pick a brand of similar composition from a different brand, that doesn’t mean it will behave in the exact same way. You might still have to use one needle size smaller or bigger. Sometimes you might have to knit a medium even though your typical size is large.

So, as a general rule of thumb, I would always pick a yarn that is close to similar to the one you are using. But even then, similar doesn’t mean the same, eh?

Reading tip: How to store yarn the right way

Anyway, that’s how to choose yarn. Feel free to comment below in case you need further help.