Crochet Yarn Weight Chart + How to Measure Wraps Per Inch (WPI)

Crochet yarn weight refers to the thickness of the yarn strand, and it plays a major role in how your finished project turns out. Using the wrong yarn weight can affect the size, drape, and overall look of your project.

In this guide, you’ll learn:

• what yarn weight means

• how to measure yarn using wraps per inch (WPI)

• how to identify yarn weight when the label is missing.

Understanding yarn weights is essential for choosing the right yarn and getting the correct fit in your projects. If the yarn weight is off, even a well-written pattern can turn out completely different than expected.

When I first got back into crocheting, I learned this the hard way. I made the Driftwood Poncho by Mama in a Stitch, which calls for a bulky (5) yarn. Instead, I used a worsted (4) yarn I already had. Halfway through, I realized my poncho was turning out way too small.

This taught me two important lessons: always check your gauge, and always pay attention to yarn weight.

Alright, let's dive in! But before we start, don't forget to save this chart for later by pinning it!

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Mastering yarn weight is one of the first steps to creating beautiful crochet projects and even writing your own patterns. Download this free, printable Yarn Weight Chart as a PDF to quickly check your yarn thickness and WPI anytime you crochet.

Bonus: This chart is perfect prep for my upcoming Pattern Writing Course, helping you choose the right yarn and get perfect sizing for your projects!

Crochet Yarn Weight Chart

There are eight thickness levels of yarn, labeled with numbers 0 to 7:

Yarn Weight Chart (Wraps Per Inch – WPI)

Yarn Weight	Name	Wraps Per Inch (WPI)
0	Lace	30+
1	Super Fine	23–30
2	Fine	16–23
3	Light (DK)	12–16
4	Medium (Worsted)	9–12
5	Bulky	7–9
6	Super Bulky	5–7
7	Jumbo	1–4

What Is Yarn Weight in Crochet?

Yarn weight refers to the thickness of the yarn, not how much it weighs on a scale. Thicker yarns create bulkier, warmer projects, while thinner yarns create lightweight and more delicate fabric.

Why Yarn Weight Matters

• Affects project size (too small or too big)

• Changes fabric texture and drape

• Impacts hook size and gauge

Even yarns labeled the same weight can vary slightly, which is why measuring WPI can be helpful.

Determining Yarn Weights With Wraps per Inch (WPI)

As mentioned, yarn weight is determined by its thickness, or diameter. But how do you measure the diameter of a single strand of yarn? By using a measurement technique called wraps per inch or WPI. You can find out WPI by following these steps:

1. Wrap yarn around a ruler or pencil

2. Keep wraps snug (not tight) and side-by-side

3. Count how many wraps fit in one inch

4. Compare your number to a yarn weight chart

More wraps = thinner yarn
Fewer wraps = thicker yarn

Alternatively, you can use a WPI tool (this one from Knit Picks is my favorite).

Measuring yarn weight with WPI becomes valuable when you don't have the label for a skein of yarn or are gifted yarn without labels.

Video Tutorial

I have a video tutorial that demonstrates how to measure wraps per inch, or WPI to determine a yarn’s weight.

What Yarn Weight Should You Use?

• Amigurumi → worsted or bulky

• Blankets → worsted or bulky

• Garments → DK or light

• Chunky projects → bulky or super bulky

What is Yarn Ply?

You may have encountered the term "ply" in yarn descriptions, like single-ply, 2-ply, 3-ply, and so on. Ply refers to the number of individual strands twisted together to form a single yarn strand. Generally, single-ply yarn is lighter than 2-ply, which is lighter than 3-ply, and so forth, but this isn't always the case.

Yarn ply can impact a yarn’s characteristics, such as thickness, strength, and texture:

• Multiple plies typically result in stronger and more durable yarn

• single-ply yarns tend to be softer and more delicate

Understanding ply is important for choosing yarn, as it can affect how a project drapes, its stitch definition, and its overall appearance. Additionally, ply influences a yarn's resilience to wear and tear, making it a consideration for projects subject to heavy use.

While understanding yarn ply is crucial, it doesn't fully indicate the yarn's weight. Although ply can influence strength and texture, it doesn't directly correspond with weight or thickness. For example, a 2-ply yarn consists of two strands twisted together, but each strand could vary in weight from lace to worsted. Ply is just one factor to consider when selecting yarn, and while you may encounter it in yarn descriptions, remember it's not a measure of weight or thickness.

Why Are There So Many Different Names for Yarn Weights?

The varying names for yarn weights can be attributed to several factors:

1. Historical Evolution: Over time, yarn weights have evolved, and different terms have been used to describe them. For example, terms like "lace," "fingering," and "worsted" have historical origins related to the types of projects or garments they were traditionally used for.

2. Regional Preferences: Different regions or countries may have their own naming conventions for yarn weights based on popular usage or industry standards. For instance, terms like "DK" (double knitting) or "Aran" are more commonly used in certain regions like the UK, while terms like "worsted" or "sport" may be more prevalent in the US.

3. Manufacturer Branding: Yarn manufacturers may also introduce their own branded names for yarn weights to differentiate their products in the market. These names may reflect specific characteristics of the yarn or be part of a marketing strategy to appeal to consumers.

4. Ease of Understanding: Some yarn weight names are chosen to make it easier for crafters to understand the thickness and suitability of the yarn for their projects. For example, terms like "super bulky" or "lace" provide clear indications of the yarn's weight and intended use.

Due to the variations in naming conventions for yarn weights, using the number system or wraps per inch (WPI) provides a clear and straightforward way to understand yarn weights without any confusion.

What Size Crochet Hook Should I Use With Each Yarn Weight?

Each yarn weight category has a range of recommended hook sizes. When substituting a different yarn weight, you'll probably need to adjust the hook size from what's specified in the pattern. Here is a rough guideline of what hook sizes are typically recommended for each yarn weight:

1. Lace (0): 1.5 mm (steel hook) to 2.25 mm (B-1)

2. Super Fine (1): 2.25 mm (B-1) to 3.5 mm (E-4)

3. Fine / Baby (2): 3.5 mm (E-4) to 4.5 mm (7)

4. Light / DK (3): 4.5 mm (7) to 5.5 mm (I-9)

5. Medium / Worsted (4): 5.5 mm (I-9) to 6.5 mm (K-10.5)

6. Bulky (5): 6.5 mm (K-10.5) to 9 mm (M/N-13)

7. Super Bulky (6): 9 mm (M/N-13) to 15 mm (P/Q)

8. Jumbo (7): 15 mm (P/Q) and larger

How Do I Substitute Yarn Weights?

Substituting yarn weights in patterns can open up a world of possibilities. Maybe you have a favorite pattern, but you want to use a different weight yarn than what's specified. Understanding how to make these substitutions can help you customize projects to your liking and make the most of your yarn stash.

Here are some tips for successfully substituting yarn weights:

1. Consider Yarn Characteristics: Take into account the characteristics of the yarn you're substituting. Is it similar in texture, fiber content, and drape to the yarn called for in the pattern? Choosing a substitute yarn with similar qualities can help ensure a successful outcome. Learn more about yarn fiber types in this blog post.

2. Adjust Hook or Needle Size: When substituting yarn weights, you will likely need to adjust your hook size to achieve the correct gauge. A thicker yarn will typically require a larger hook size, while a thinner yarn may need a smaller size. Make a gauge swatch with your chosen yarn and adjust your hook size as needed to match the pattern's gauge. You can learn more about crochet hook sizes here.

3. Test Before Committing: Before diving into your project, make a small swatch with your chosen substitute yarn to test how it works up with the pattern stitch. This will give you a chance to assess the fabric's drape, texture, and overall appearance before committing to the entire project. This is also a great time to measure gauge.

With these tips in mind, you can confidently substitute yarn weights in your favorite patterns and create beautiful projects that reflect your unique style and creativity.