Yarn Weight Conversion Chart: The Complete CYC 0-7 Reference Guide

📅 Last updated: February 2026

Understanding the CYC Yarn Weight System

The Craft Yarn Council (CYC) established a standardized yarn weight system to bring consistency to the global yarn market. Before this system, yarn was described with inconsistent terms — what one brand called "sport weight," another might market as "DK" or "light worsted." The CYC system assigns numbers 0 through 7, each representing a specific range of yarn thickness, with associated gauge ranges and recommended hook/needle sizes.

This numbering system appears on yarn labels globally, usually inside a small skein icon with the weight number displayed prominently. When a pattern calls for "worsted weight" yarn, it's referring to CYC category #4. When a label shows the number 4 inside the yarn symbol, you know it falls within the worsted weight range. Understanding this system is fundamental to yarn shopping, pattern selection, and successful substitution.

It's important to note that weight categories are ranges, not exact specifications. Two yarns both labeled "#4 Worsted" may feel noticeably different in thickness. One might sit at the lighter end of the range (closer to DK), while another sits at the heavier end (closer to bulky). This is why gauge swatching is essential alongside weight matching. See our gauge guide and yarn substitution guide for more on verifying yarn equivalence.

Complete Yarn Weight Conversion Chart (CYC 0-7)

Each Yarn Weight in Detail: Best Uses and Characteristics

Lace (#0): The finest yarn weight, lace is used for delicate shawls, doilies, and intricate lacework. Projects at this weight require patience and skill but produce stunning, heirloom-quality pieces. Lace projects work up slowly due to the small hook and high stitch count.

Fingering (#1): Also known as sock yarn, fingering weight is the go-to for socks, lightweight shawls, and detailed colorwork projects. It's also popular for amigurumi because the tight stitches prevent stuffing from showing. Projects are moderately time-intensive but produce light, wearable items.

Sport (#2): A versatile middle-ground between fingering and DK, sport weight creates lightweight baby items, spring garments, and accessories. It's less common in stores than worsted but highly valued by intermediate to advanced crocheters for its excellent stitch definition.

DK (#3): DK (Double Knitting) weight is the most popular weight outside North America. It creates lighter garments and accessories than worsted — ideal for year-round wearables. DK yarn works up faster than sport while maintaining a refined, non-bulky look.

Worsted (#4): The king of yarn weights. Worsted is the most widely available, most affordable, and most commonly used category globally. It's the default choice for blankets, hats, scarves, sweaters, and virtually any project. If you're unsure what weight to buy, start with worsted.

Bulky (#5): Bulky yarn creates warm, thick fabric that works up quickly. Popular for winter accessories (hats, cowls, mittens), quick blankets, and chunky sweaters. Projects at this weight are excellent for beginners because the large stitches are easy to see and count.

Super Bulky (#6) and Jumbo (#7): These extreme weights produce fabric very quickly — a scarf in super bulky can be completed in an hour. However, the finished items are heavy and bulky. Jumbo weight (used for arm knitting and extreme crochet) creates statement pieces but requires significant physical effort and space to work.

WPI: The Universal Yarn Thickness Test

WPI (Wraps Per Inch) is the most reliable way to objectively measure yarn thickness, independent of brand labels. To perform the WPI test: wrap yarn snugly (but not stretched) around a ruler or pencil, with wraps touching but not overlapping. Count the number of complete wraps that fit in exactly one inch.

This measurement directly corresponds to yarn weight categories and is especially useful when dealing with unlabeled yarn, hand-spun yarn, or yarn from brands that don't use CYC categories. See the WPI column in our conversion chart above for reference values. This test is also essential when substituting yarn — matching WPI ensures your substitute is the same effective weight.

International Yarn Weight Names

Different countries and regions use their own terminology for yarn weights, which can create confusion when following international patterns. Australian and UK patterns often use "ply" designations (4-ply, 8-ply, 12-ply), while Japanese patterns use their own weight system. Here's how the most common international terms map to CYC categories:

Doubling Up: Combining Yarn Weights

Holding two strands of thinner yarn together approximates a heavier weight. This technique — called "double-stranding" or "holding double" — is useful for using up stash yarn, creating unique color blends, or substituting when you can't find the right weight. Common combinations:

Frequently Asked Questions