How to figure out yarn weight


Yarn weights explained: a tutorial on learning how to figure out yarn weight using the WPI (wraps per inch) method!

We all have mystery balls, skeins, and oddments of yarn hidden amidst our stashes. Sometimes you rediscover the perfect yarn, only to realise that you lost the label, and you have no memory of purchasing it. was it 4-ply or DK who knows? It's now officially a Mystery Yarn. 

Instead of endless swatching to try to suss out what its classification is, we like the WPI (wraps per inch) method. It was developed as an industry standard, which is helpful when considering regional differences in how yarn is classified. 

Important: you should still knit a swatch before starting a garment project, especially when using super chunky yarns! 

How to figure out yarn weight using the WPI method

Another important note: plies used to determine the thickness of a yarn, but with the advent of more modern spinning techniques and fibres, this is no longer an accurate way to determine a yarn's weight.

To achieve this, you're going to need a few things we can almost guarantee you already have hanging around your stash. The Mystery Yarn, a tape measure or ruler, and a pencil (or knitting needle, the circumference doesn't matter). 

Wondering why the circumference doesn't matter? It's because we are studying the thickness of the yarn, which isn't affected by the width of whatever tool you are using. 

Yarn weights explained

First off, have a look at the table below. It includes US and UK classifications for yarn weights and the industry standard classifications for each yarn weight. 

Use this Wraps per Inch chart to figure out yarn weight

As you can see, anything less than 6 wraps per inch (or 2.5cm) is classified as a super chunky or super bulky yarn. That makes for quite a wide range in yarns, which is why it's very important to consider other factors when looking for a substitute yarn, like tension and metres per ball or skein. 

To figure out your wraps per inch, you're going to wrap the yarn around your pencil. You will wrap about 2 inches (5cm) up the pencil to get an accurate measurement. Make sure you don't pull the yarn too tight or squish it down, as that will impact your measurement. 

Yarn weights explained

Our Mystery Yarn has about 8-9 wraps per inch. That would make it a slightly heavier aran, or a lighter chunky weight yarn. It's not uncommon for some yarns to sit on the cusp of two weights; these guidelines are meant to help you get an idea of what you have. Once you choose a project for your yarn, you'll need to knit a tension swatch to check for that. 

Tension is important because a tight knitter might find that this slightly chunky yarn works up perfect for an aran weight pattern, whereas a loose knitter may find that it's far too big. If you want to learn more about tension, read our blog post on it! 

How to figure out yarn weight