How to Choose the Right Yarn Weight for Knitting (Without Overthinking It)

When you start knitting and are picking your first project, you immediately run into a wall of new terms to learn about the weight of the yarn you're using. So what does yarn weight actually mean?

What Does Yarn Weight Actually Mean?

The "weight" of a yarn isn't how much the ball of yarn weighs. Most yarns come in balls or skeins measured in total ounces or grams, but they can all be different weights. The weight of the yarn is most similar to the thickness of the yarn or, thought of another way, the weight per yard or meter. The thicker the yarn is, generally more grams of wool are required to make one meter of yarn. A yarn that is 200 yards in a ball of 100 grams is approximately twice the thickness of a yarn that has 400 yards in a ball of 100 grams.

This isn't always totally true, though! It would be as simple as that if all yarns were made with the same kind of wool and made the same way. They're not! Wool comes from all kinds of breeds of sheep that have many different characteristics. Yarns from those wools are made in many different ways. Without going into all the details, these differences mean that some yarns are thicker than others at the same number of yards in the same weight of the ball.

For example, two yarns that both have 200 yards in a 100-gram ball could be different thicknesses if you measured their actual diameter because they are made in a less dense way. You might hear that a yarn has "loft" or is "fluffy" or "spongy". Those kinds of words often mean the yarn is thicker than you'd expect for the yardage in the ball. On the opposite end, a yarn that is "smooth" or "sleek" or "dense" often means that the yarn is thinner than you may expect. Neither is inherently a good thing or a bad thing, but it gives you more information about the yarn and what you can expect from the fabric.

These differences in actual thickness affect the size of your stitches and therefore your knitting gauge. A thinner yarn will usually give you smaller stitches and a thicker yarn will give you larger stitches, even if the yardage per gram is exactly the same. This is the main reason that you may find a yarn with a weight label that is different from another yarn with the same yardage. The weight names try to show a knitter what kind of gauge you can expect when the yardage per weight itself doesn't tell the whole story.

But What About the Yarn Weight Names?

OK, so what is the story with the yarn weight names? There are eight common weights of yarn, depending a bit on the yarn brand, the country of origin, and how much they're broken up. Generally, these are lace, fingering, sport, DK, worsted, aran, bulky, and chunky. You will sometimes see cobweb or thread for yarns even smaller than lace and super chunky above chunky.

These names come from the roots of the English language in the English countryside. Fingering comes from an Anglicization of the old French "fin grain" or "fin graine" for fine grain. DK stands for "double knitting", most likely reflecting that it's the double thickness of what was the semi-standard yarn being used historically (more on this semi-standard yarn below!). Worsted comes from the name of an English village (Worstead) known for its wool and fabric industry from the 12th century. Aran comes from the name of the Aran Islands off the coast of Ireland. Unfortunately, the origin of Sport as a yarn weight isn't clear, but it may relate to its use in knit sportswear.

Wait, What About 4ply Yarn?

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Apart from, but related to, the yarn weights listed above is the "ply" system. This has its roots in the United Kingdom and the semi-standard yarn I referred to above. Historically, wool was spun to a semi-standard ply thickness and then plied together to make yarns, with more plies making the yarn thicker. A "4ply" yarn is the remnant of that system, even when the yarns no longer have to be made from a number of standard-thickness plies, and is approximately a fingering weight. In Australia and New Zealand in particular, this system goes further even today to 8ply, 10ply, and even 12ply to be approximately DK, worsted, and bulky, regardless of the actual physical plies.

What Yarn Do I Want to Use?

Generally, yarn weight labels are a good starting point for picking a yarn for your project. Knitting a gauge swatch and feeling the fabric to see if it's what you want in your project is going to be the best final indicator. But starting with the yarn weight called for in your pattern is a great place to start. You can find yarns at The Woolly Thistle separated by weight.

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The lighter yarn weights (fingering and sport) are commonly used for socks, shawls, and lightweight sweaters. The fabric can have more drape and flow and is thinner than other yarn weights, meaning it's usually less warm and may be more suitable for three-season wear. They're also used frequently in double-layer hats and in colorwork for their small stitch size (giving more detail in a motif).

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Mid-weight yarns (usually DK and worsted) are very often used for sweaters and hats. These middle weights hit a nice balance between fineness and having to knit fewer stitches than for the lighter weights. These yarns are usually not used for socks primarily because the thicker sock probably won't fit in a person's normal shoe. Aran weight is a name more commonly used in the United Kingdom and can be somewhat interchangeable with what we think of as worsted weight in North America. These yarns are really good for beginners because they're not too thick to handle easily, but they do provide more positive feedback as you see the progress you make.

Worsted vs. Aran Weight Yarn
Worsted and aran weight yarns are a great example of how yarn terminology can vary across countries and traditions. In many cases, the two names are used for the same general mid-weight category, with “worsted” being more common in North America and “aran” more common in the United Kingdom. Modern yarn guides sometimes separate them, placing aran slightly heavier than worsted, but there is plenty of overlap. As always, gauge and the fabric you create are better guides than the name printed on the label.

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Heavier weights (bulky and up) can be used for very quick knits, but also for felting home goods like potholders and slippers. These weights are somewhat less common because they can be very warm and may only be suitable for the coldest winter days.

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Laceweight is interesting. It is thinner than fingering weight, but can often be knit more loosely and on larger needles to knit open lacework. You don't usually see laceweight knit into a solid fabric. However, laceweights also include the popular mohair + silk, mohair + nylon, and suri alpaca + silk combinations. They are also usually either knit very open or held doubled with another yarn.

Can I Use a Different Yarn Weight?

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Absolutely! There is a lot of overlap between the different yarn weights and sometimes you'll even see a yarn described as a "light" or "heavy" version of one of these weights. You may also find a yarn labeled a DK that you like the fabric knit up at the gauge for a pattern labeled worsted weight or sport weight. Trusting your swatch and the fabric you want is the best guide.