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Understanding Yarn Weight, Part 1

You've heard terms such as DK weight and sport weight thrown around. But what do they mean? And what weight is sock yarn? (I'll be honest from the beginning. This article is going to completely confuse all the yarn weight determinations—don't worry. We'll come back to this topic in another tip and clear things up!)

What Is Yarn Weight?

The term yarn weight is used to describe the thickness (diameter) of a yarn. This can be measured in various ways and the distinction between different weights isn't always perfectly clear, but it's a way to categorize yarns so you have a starting idea of what needle size to use and the size of the stitches that will be made using that yarn. It also is important information to know if you want to use a different yarn than the one used in a pattern and still get similar results.

Names for Yarn Weights

Part of the confusing issue with yarn weights is that people often use different names when talking about the same thing. For example, the terms "fingering," "sock," "4-ply," and "super fine" and the number 1 all refer to the same weight of yarn. The Craft Yarn Council has a table of "standard weight definitions" and encourages yarn companies to use the numbering system, but not everyone does, and even though there is a listed "standard," because of differences in fiber content and yarn construction, those standards can't always be matched perfectly.

Using Ply Number

Looking at my example list above, you see the term "4-ply" being used for a fingering weight yarn. But if you've looked at some of my yarn bases, for example, you'll notice that I say Round Table Yarns Guenevere is a fingering weight 2-ply yarn. How can that be?

Here's the deal: In some countries (UK, Australia), the terms 4-ply or 6-ply are used to indicate the weight of the yarn and have nothing to do with how many actual plies the yarn has--or rather it has no connection today. Historically, yarn thickness was created by taking a certain number of singles and twisting them together. The singles would always be the same size, so the thickness of the finished yarn depended on how many of those singles (or plies) were used to create the yarn. Since all of the singles started off the same, this created uniformity in the final yarn. But not all singles (plies) are created the same these days, so this terminology is no longer accurate. So the construction of the yarn (how many plies it actually has) doesn't translate to the thickness of the yarn these days. Yet the terms are still used in some places. Confusing, right?

Measuring WPI

One method of measuring yarn weight is wraps per inch (WPI). To take this measurement, you use a ruler (or a WPI tool) and wrap the yarn around it, counting the number of wraps that fit within one inch. Let's say your yarn measures 14 WPI. According to this chart, that means your yarn is a DK weight. But then if you look at this chart, the yarn would be fingering weight! I've personally been frustrated by these issues with measuring WPI for my handspun yarn and still don't have a clear answer for why there seem to be two very different charts for the measurements. Then add to the problem that how many wraps you get in one inch can depend a lot on how tightly you wrap the yarn (do you push the wraps together? do they have space in between? have you flattened out the yarn?) So WPI doesn't seem to be the best method for determining yarn weight.

Measuring Gauge

Going back to the CYC table, each yarn weight has a specific gauge (both knit and crochet) associated with it. For knitting, the gauge is measured using stockinette stitch. We're going to skip over the best ways to knit and measure a gauge swatch (because that's a whole separate topic!) and just look at the listed gauges. If your swatch measures 20 stitches over 4 inches, then the yarn is a worsted weight. Easy enough, right?

But wait. Doesn't it matter what size needles you use? Yes and no. The needle size does affect the gauge for sure. But I could use large needles on a fingering weight yarn and knit a loose fabric and end up with those same 20 stitches per inch as I did with a worsted weight yarn. Or I could use tiny needles and a worsted weight yarn and end up with 28 stitches per inch, which technically is classified as a fingering weight yarn (although I'd probably hate every minute of the actual knitting because the stitches would be so tight!). But the yarn itself doesn't change classifications based upon the gauge that you personally get. Instead, the yarn gauge range for each yarn weight is based on a fabric that is not too loose and not too tight—so something "average," however that is determined.

So each yarn weight will have a recommended needle (and hook) size listed. Think of it as a starting point but don't feel like you need to stick to the size listed. Depending on your own personal knitting style and the drape of fabric that you want to create, you may need to change needles sizes. And there's nothing wrong with that!


Have I completely confused you? That's definitely not my goal! What I want to do instead is to acknowledge that this whole yarn weight system can be really confusing. So if you're wondering how on earth to determine what weight a yarn is, you're definitely not alone!

This is a big topic and I don't want to pile on too much information all at one time, so I'll be back in the next tip to start sorting through the confusion to help you figure out this whole yarn weight thing as well as discussing why it is actually important to consider but also when the yarn label can be ignored.

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