If you feel confused and overwhelmed by all of the different yarn numbers, yarn names, yarn weights and yarn sizes that yarn is made in, then the following will definitely help to explain the US classification system!
Yarn is a gorgeous and dynamic fiber, and probably one of the main reasons you love crochet so much!
But, it’s complicated…
Let’s cover the basics of yarn, so you can learn more about how to choose the best yarns for all your crochet projects.
Estimated reading time: 6 minutes
Table of contents
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What are yarn weights?
Yarn weight is not about how much a ball or skein of yarn weighs in ounces, grams, or pounds (even though that would make a lot of sense, right?).
In the yarn world, weight actually refers to the thickness of the strand itself—also known as gauge.
Think of it like this: yarn comes in different sizes, just like clothing.
Yarn weight helps you determine which size of yarn is best suited for your project, whether it’s delicate lace or a chunky, snuggly blanket.
Knowing yarn weights helps you choose the right yarn for your project, match patterns correctly, and even substitute yarns with confidence.
So next time you see the term yarn weight, just remember—it’s all about thickness, not heaviness!
How many yarn weights are there?
In the US, yarn is manufactured and classified into 8 main categories (from 0 to 7).
Weight 0 is the smallest size, and includes crochet thread.
Weight 7 is the largest of the sizes on the yarn weight classification chart.
How is yarn weight classified?
Yarn is classified into a weight category based on how many single crochet stitches can be crocheted into a four inch space of fabric.
These categories are guidelines that have been outlined by the Craft Yarn Council, reflecting information collected and shared by industry leaders like yarn manufacturers.
Wraps per inch (WPI) is another popular method of classifying yarn by weight.
The number of times a strand of yarn can be wrapped into a one inch space is a quick way to determine the weight classification, and type.
How can I tell what weight my yarn is?
Yarn labels typically include a weight category by number (0-7) and name (Lace, Super Fine, Fine…).
A yarn label may also include the type (or, sub-category) too (example: Sock, Baby, DK…).
The below label example shows Weight 4 Medium yarn.
Swatches are a great tool for measuring the gauge of your yarn.
Gauge refers to the number of stitches across (width) and rows down (height) within a fabric, typically measured in a 4″x4″ square.
Not every crochet project requires precise sizing, so swatching isn’t always necessary.
However, if your project does depend on size—like garments or fitted accessories—checking gauge is essential.
By crocheting a swatch, you can see your stitch and row measurements, helping you determine how your finished piece will turn out and whether any adjustments are needed.
Yarn Weight Chart
For each of the 8 categories, there are also sub-categories (types) that help to further define the thickness.
- Weight 0 = Lace: 30-40 Sts per 4”
- Fingering 10 Count Thread
- Weight 1 = Super Fine: 21-32 Sts per 4”
- Sock
- Fingering
- Baby
- Weight 2 = Fine: 16-20 Sts per 4”
- Sport
- Baby
- Weight 3 = Light: 12-17 Sts per 4”
- DK
- Light Worsted
- Weight 4 = Medium: 11-14 Sts per 4”
- Worsted
- Afghan
- Aran
- Weight 5 = Bulky: 8-11 Sts per 4”
- Chunky
- Craft
- Rug
- Weight 6 = Super Bulky: 7-9 Sts per 4”
- Super Bulky
- Roving
- Weight 7 = Jumbo: 6 or less Sts per 4”
- Jumbo
- Roving
Does yarn weight matter?
If the size of your project matters, the size of your fiber should too!
The weight, or size, of a yarn will determine the size of the stitches you crochet and the fabric you make.
As you can see from the Yarn Weight Classification chart, there are 3 types of Weight 4 Medium yarn: Worsted, Afghan, Aran.
Each one of those types will create a slightly different single crochet stitch count over a four inch span.
This means that each type of Weight 4 Medium yarn will work up to be a slightly different size.
If you’re following a pattern that lists a specific yarn category and type, then use that yarn to create the same size project.
Or, if you’re substituting yarn, be sure to use the same yarn category and type for the closest match.
For more about substituting yarn, here are some helpful tips: Understanding Yarn Substitution: An Easy Reference For Crocheters
Test out your new skills!
Go through your stash and choose at least 3 in the same category (0 to 7).
Using single crochet stitches, work up 10 stitches by 10 rows in each yarn.
You can use our quick and easy video to crochet a single crochet for help to work up a 10 stitch by 10 row swatch.
Then, measure each one to see how they differ.
Did you learn anything new about yarn?
Share a picture of your 3 yarns swatches, let us know what yarn you used, and tell us how your stitches measure up, right here in our community!
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Salena
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