In this post, we’ll discuss how to measure yarn using the Wraps per Inch (WPI) technique.
Think of all the times that you went through your yarn stash and found yarn scraps without the yarn labels. Maybe, when you were organizing your yarn, you found a stray skein of mystery yarn. Or perhaps you wanted to buy some thrift yarn but didn’t because it didn’t have its ball band.
If you’ve ever wondered how to determine yarn weight without a label, this post is for you. I’ll show you how to find yarn weight by measuring yarn thickness.
Before we get to measuring yarn, let’s define what wraps per inch means.
What are Wraps per Inch (WPI)?
The term Wraps per inch (WPI) is just as the name suggests. It refers to the number of times a yarn wraps around to equal one inch.
This technique is a quick way to know which yarn weight or yarn group you’re using. Being able to determine yarn gauge is important for a number of reasons. Let’s quickly talk about a few.
Shown above are:
- (0) Lace weight yarn shown in variegated crochet thread with 31 WPI.
- (1) Super fine weight yarn shown in Wayback Yarns Truly Twisted "Dusky Dreams," sock yarn in 80% Superwash wool / 20% Nylon. Shown with 17 WPI.
- (2 ) Fine yarn in 100% wool (non-superwash), hand dyed yarn with 12 WPI.
Why Yarn Gauge is Important
The gauge of a yarn has everything to do with the knit or crochet projects you want to make. If your yarn label doesn’t show a yarn symbol, doesn’t include a label, or if you’re wanting to knit with handspun yarn, you’ll need to figure out yarn gauge.
The easiest way to do this is to figure out the WPI yarn weight. You can learn more about the different yarn weights here.
Measuring yarn using the Wraps per Inch technique is easy to do. Ready to get started? Let’s go.
Shown above are:
- (3) Light weight (DK yarn) shown in Cascade Yarns Anchor Bay in Silver, a cotton blend yarn with 14 WPI.
- (4) Medium yarn shown in Cascade 220 Worsted weight 100% Peruvian Highland wool with 11 WPI.
- (5) Bulky weight in Premier Puzzle Yarn in Hangman colorway with 8 WPI.
How to Measure a Yarn’s WPI
To measure yarn weight, you can use a wraps per inch tool to measure, your knitting needle or crochet hook, or you can use the ruler in your knitting kit. For this post, I’ll demonstrate with my ruler.
First, find the end of the yarn. Next, take your ruler and hold the yarn tail against the back of the ruler. Begin wrapping the yarn (or turning the ruler) around until you have 1” worth of yarn wraps.
Wrap your yarn casually around the ruler. Wrapping too tightly can throw off the total measurement. Be sure to keep the yarn wraps flat and avoid overlapping the strands.
You can also wrap yarn for a couple of inches. Sometimes this helps, especially with thicker yarns weights, to get a more accurate reading. If you do this, just remember to divide the total wraps by the number of inches.
If you’re only wrapping yarn for an inch, just count the number of yarn wraps that are on the ruler, as shown below. Compare the number of wraps against the WPI Yarn Chart below.
Yarn Wraps per Inch Chart
Below you'll find a handy wraps per inch chart. Keep in mind that there will always be variables between yarns. For example, some yarns may be marked as one weight but wrap out at another. This is one of the many reasons why it's so important to knit a gauge swatch.
So, without further ado, here are the number of wraps per Inch for each weight:
|(0) Lace||30 - 40+ WPI|
|(1) Super Fine||14 - 30 WPI|
|(2) Fine||12 - 18 WPI|
|(3) Light||11 - 15 WPI|
|(4) Medium||8 - 12 WPI|
|(5) Bulky||6 - 9 WPI|
|(6) Super Bulky||5 - 6 WPI|
|(7) Jumbo||1 - 4 WPI|
*NOTE: The wraps per inch technique may help you determine the weight of MOST yarns. It may not be effective when trying to determine WPI for novelty yarns.
That wraps up, literally, our discussion on measuring yarn for wraps per inch. I hope you enjoyed this post. If you have questions or just want to share your thoughts, please drop me a comment below.