CYC Standard Yarn Weight System
Based on the Craft Yarn Council (CYC) Standard Yarn Weight System. Use this chart as an industry reference when comparing yarn categories or selecting starting hook sizes.
Important Guidance on Hook Sizes:
Recommended hook ranges are starting points only. Letter designations can vary between manufacturers (e.g. an "H" hook is 5.0 mm in most brands, while "I" can be 5.25 mm or 5.5 mm). Always check the millimeter diameter stamped on the hook shaft and crochet a gauge swatch to evaluate fabric drape.
| Category | Common Industry Names | Wraps Per Inch (WPI) | Recommended Hook (mm) | Typical Single Crochet Gauge | Common Applications |
|---|---|---|---|---|---|
0Lace | Fingering 10-count crochet thread, Cobweb | 30–40+ WPI | 1.6 mm – 2.25 mm (Steel hooks 6–8) | 32–42+ stitches per 10cm | Doilies, delicate vintage lace edgings, micro-crochet jewelry. |
1Super Fine | Sock, Fingering, Baby, 4-Ply (UK/AU) | 19–22 WPI | 2.25 mm – 3.5 mm | 21–32 stitches per 10cm | Socks, lightweight shawls, baby sweaters, fine accessories. |
2Fine | Sport, Baby, 5-Ply (UK/AU) | 15–18 WPI | 3.5 mm – 4.5 mm | 16–20 stitches per 10cm | Lightweight garments, baby blankets, summer tops. |
3Light | DK (Double Knitting), Light Worsted, 8-Ply (UK/AU) | 12–14 WPI | 4.5 mm – 5.5 mm | 12–17 stitches per 10cm | Cardigans, lapghans, winter shawls, amigurumi. |
4Medium | Worsted, Afghan, Aran, 10-Ply (UK/AU) | 9–11 WPI | 5.5 mm – 6.5 mm | 11–14 stitches per 10cm | Standard blankets, winter hats, mittens, sweaters, home decor. |
5Bulky | Chunky, Craft, Rug, 12-Ply (UK/AU) | 7–8 WPI | 6.5 mm – 9.0 mm | 8–11 stitches per 10cm | Quick chunky blankets, thick scarves, baskets, slippers. |
6Super Bulky | Super Chunky, Roving | 5–6 WPI | 9.0 mm – 15.0 mm | 5–9 stitches per 10cm | Heavy winter cowls, arm-crochet rugs, oversized floor poufs. |
7Jumbo | Giant roving, Chunky tube yarn | 1–4 WPI | 15.0 mm and larger | 6 or fewer stitches per 10cm | Giant floor rugs, extreme hand-crochet throws. |
How to Measure Wraps Per Inch (WPI) for Unlabeled Skeins
If you have mystery yarn without a ball band, the most reliable physical test of yarn category is Wraps Per Inch (WPI):
- Wrap the mystery strand around a standard wooden pencil or rigid ruler for several inches.
- Ensure the wraps lie touching side-by-side with gentle, uniform tension, without overlapping and without stretching the fiber tightly.
- Place a rigid ruler against the wrapped area and count how many complete strand widths fit inside exactly one inch (2.54 cm).
- Compare your count to the WPI column in the reference chart above. For example, 10 wraps in one inch indicates standard #4 Worsted weight.