Yarn thickness is standardized by the Craft Yarn Council (CYC) into categories 0 through 7. Matching the pattern's category is the single most important factor in a project coming out the intended size — and it drives every yardage estimate.
The CYC 0–7 chart
| # | Name | Also called | Needles | Hook | Best for |
|---|---|---|---|---|---|
| 0 | Lace | Fingering 10-count | US 000–1 (1.5–2.25 mm) | B-1 | Delicate shawls, mesh |
| 1 | Super Fine | Fingering, sock | US 1–3 (2.25–3.25 mm) | B-1–E-4 | Socks, baby garments |
| 2 | Fine | Sport, baby | US 3–5 (3.25–3.75 mm) | E-4–7 | Baby blankets, light sweaters |
| 3 | Light | DK, light worsted | US 5–7 (3.75–4.5 mm) | 7–I-9 | Cardigans, hats, sweaters |
| 4 | Medium | Worsted, afghan, aran | US 7–9 (4.5–5.5 mm) | I-9–K-10.5 | The universal standard; great for beginners |
| 5 | Bulky | Chunky, craft, rug | US 9–11 (5.5–8 mm) | K-10.5–M-13 | Fast beanies, scarves, rugs |
| 6 | Super Bulky | Roving | US 11–17 (8–12.75 mm) | M-13–Q | Thick blankets, quick gifts |
| 7 | Jumbo | Giant | US 17+ (12.75 mm+) | Q+ | Arm-knitting, statement throws |
Reading the label
The category appears on the ball band as a small skein symbol with the number inside. Around it you'll find the two numbers that matter most for buying: length per skein (yards/meters) and weight (grams/ounces). Those two, plus the category, are all an estimator needs.
Shortcut: point the SkeinSense scanner at any ball band and it reads brand, length, weight and category in one shot — then tells you how many skeins your project needs, and why.
Try the label scanner — free in SkeinSense →