7 Yarn Weights and the Language to Understand Them

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Woman carrying a basket full of yarn and a text overlay which says "Knitting Skills: 7 Yarn Weights and the Language to Understand Them, learnknittingonline.com, " followed by the LKO lettermarkLearning the different yarn weights doesn’t mean you need to earn a university degree to understand them. While there are quite a few terms that you may or may not be familiar with, the numbering system used to describe and differentiate between all the possible yarns isn’t as difficult to learn as you might think.

Because of the sheer number of categories, sub-categories, and further subsets, a lot of confusion surrounds identifying the very yarn you require. But by understanding a few basic rules, I hope to dismiss a lot of the confusion with simple facts that will hopefully help you ‘weave’ your way through it all.

How Yarn Size is Determined

While many will think of yarn as being made up of a single strand, they can in fact be made up of several. Funnily enough, a single strand that is spun together with others, is called a ‘single’. The material is wound in a certain direction to form the single. Singles can then be spun together to form 2-ply and 3-ply and so on.

It’s also worth noting that as singles are spun together to form 2-ply etc, they are spun in the opposite direction to how the single was spun. Spinning singles together in the opposite direction increases the strength, consistency and durability of the finished yarn.

Once the required singles are spun together, they form the final yarn that is wound and readied for sale. The number assigned to the yarn isn’t based on the final yarn thickness. It is based on the individual ‘single’ thickness, used to create the yarn.

What is a Ply?

2-ply, 3-ply, 4-ply, and so on. These are the numbers many use to determine which yarn to use for their project. But why are yarns spun together to form plies? It all comes down to strength, balance, and durability.

Using a single-ply yarn will mean your project is more susceptible to pilling. Piling is when little strands of fiber slip from your knitted works and create little wads. The single is also a lot weaker, which leaves the material looking worn a lot quicker, due to the strands coming apart.

By spinning 2 singles together, not only do you increase the strength of the yarn, but once you knit your project, its appearance looks more balanced and textured. The more plies you add, the stronger and denser your yarn is, providing more density to your project.

There is another option that many enjoy. Plying pre-plied yarns together, such as 2 lots of 2-ply, creates what’s called a cabled yarn. There are different options here as well, such as considering which direction the original yarn was spun, or which direction the 2-ply was spun when combined.

Spinning the products in either the same direction or opposite direction will give your yarn more character in appearance, more strength, and fantastic stitch definition. They don’t all need to be spun in the same direction either. Mixing things up produces what’s called ‘boucle’.

Understanding how yarns and plies are created helps you understand the many effects they have on your finished product, the changes in appearance and the wear and tear of your item.

The Weight Issue

When is weight not weight? When it’s a thickness. Confused? I don’t blame you. A yarn’s weight has nothing to do with what it weighs. Not these days, anyway. Back in the day. when most people were knitting with wool, ply had a lot do with the weight of the yarn. Because of that, a single-ply was always a consistent size.

This meant that people knew how thick a 4-ply yarn was because they knew what size a single was. But these days, everything has been formally standardized by the Craft Yarn Council of America. It does away with a lot of confusing terms and brings everything back to simple numbers that are easy to understand, regardless of where you are around the world.

The Question About Needles

The size of the yarn will also determine the size of the knitting needles you’ll need to use with it. And what it comes down to is the size of the stitches and the thickness of the yarn to create those stitches.

When choosing your next project, the pattern you’ll use will suggest a certain yarn ply as well as which needle size to use. If used correctly, what you’ll end up with is a certain number of stitches that will comfortably fit onto your needle as you work.

Always begin any project by first creating a swatch. This small sample will ensure you understand how the project will progress. Only fitting 10 stitches per every 4 inches instead of the supposed 14 will make a significant difference when knitting an entire sweater.

The Proper Yarn Weights

Size 0: Lace

This lace yarn is usually cotton and isn’t normally sold in skeins. You’ll find this delicate thread sold by the ball. It is sometimes referred to as ‘fingering yarn’ although Size 1 type of yarn is also sometimes called this. The perfect needle size for this sized yarn is 000 to 1.

Size 1: Superfine

This superfine yarn falls under the fingering category of yarns. This defines the yarn weight, the way it’s spun, and fiber content. Always create a swatch when using this size as fingering also refers to other sized yarns. The best needle sizes for this yarn are 1 to 3.

Size 2: Fine

Fine yarns are also sometimes called sport’s yarns. The yarn is a nice lightweight and simple to work with. Suitable needle sizes are 3 to 5.

Size 3: Light

This yarn is also known as either “light-worsted’ or ‘double-knitting’ yarn. These names are used interchangeably but technically mean the same thing. Some call this yarn the ‘goldilocks’ yarn because it’s suitable for most projects, falling into that ‘perfect for everything’ kind of category. The perfect needle sizes for this are 5 to 7.

Size 4: Medium

Medium yarn is also known as ‘worsted-weight’ yarn, ‘afghan’ yarn or even ‘Aran’. This yarn is mostly preferred for anyone starting to knit as it gives a great visual representation of the stitches for a beginner. The suitable needle size for this anywhere from 7 to 9.

Size 5: Bulky

Also known as ‘chunky’, bulky yarn is substantially thick, making working with it a fun change from the thinner varieties. Suitable needle sizes that work well with bulky yarn are 10 or 11.

Size 6: Super Bulky

This yarn is also called ‘super chunky’. Because of its substantial size, it can play havoc on your fingers. Be ready to experience some finger cramps if you forget to warm up first. Perfect needles to use with this yarn are 13 to 15.

Final Thoughts On Yarn Weights

There is another sized yarn called Jumbo, although this is mostly used for arm knitting. Different sized yarn provides a world of possibilities for projects you might consider. By mixing things up from one project to the next, you’ll find variety will often pique your interest if you happen to lose your hunger during a, particularly testing job.

If you enjoyed this article, why not check out this excellent article about fixing knitting mistakes: Fixing Knitting Mistakes: Do You Tink or Do You Frog?


  1. Thank you so much for the yarn weight information. I do find that English DK has got thinner over the years. I knit daily and always look forward to your email. I don’t have enough knitting hours in a day to knit!

  2. I have knitted a 100% wool cardigan (size 4) and that makes balls of fluff ( pills), now I am knitting again from the same quality (left overs) an other cardigan and I am worried same problem, would you know an solution?, maybe a day in diluted vinegar before wearing? or some thing like that, I have no idea, I hope you know the answer, thank you.

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