The Yarn Weight System Explained
The Craft Yarn Council (CYC) established a standardized numbering system from 0 to 7 that classifies yarns by thickness. This system is now printed on most yarn labels worldwide, making it easier to substitute yarns across brands.
The categories are: 0 (Lace), 1 (Super Fine/Fingering), 2 (Fine/Sport), 3 (Light/DK), 4 (Medium/Worsted), 5 (Bulky), 6 (Super Bulky), and 7 (Jumbo). The number refers to the weight category, not the number of plies or any measurement of the yarn itself.
Weight Categories in Detail
Lace (0) is the thinnest yarn, with 32+ stitches per 4 inches on US 000–1 needles. It's used for delicate shawls, doilies, and fine lacework. Skeins typically contain 400–1,000+ yards.
Fingering/Sock (1) knits at 27–32 stitches per 4 inches on US 1–3 needles. It's the standard for socks, lightweight shawls, and detailed colorwork like Fair Isle. This weight has seen a huge surge in popularity.
Sport (2) knits at 23–26 stitches per 4 inches on US 3–5. It sits between fingering and DK, great for baby items and lightweight garments.
DK (3) knits at 21–24 stitches per 4 inches on US 5–7. DK stands for Double Knitting, a British term. It's versatile for garments, accessories, and blankets.
Worsted (4) is the most popular weight worldwide, knitting at 16–20 stitches per 4 inches on US 7–9. Most beginner patterns and the majority of yarn available in craft stores are worsted weight.
Bulky (5) knits at 12–15 stitches per 4 inches on US 9–11. It works up quickly and is popular for chunky accessories, quick blankets, and winter garments.
Super Bulky (6) knits at 7–11 stitches per 4 inches on US 11–17. Extremely fast projects. Popular for arm-knitting and chunky home decor.
Jumbo (7) is the thickest, using US 17+ needles or even PVC pipes. Used for extreme chunky blankets and novelty projects.
US, UK, and Australian Yarn Terms
The same yarn weight often has different names in different countries, which causes confusion when following international patterns.
US Fingering = UK 4-ply = AU 4-ply. US Sport = UK 5-ply = AU 5-ply. US DK = UK DK = AU 8-ply. US Worsted = UK Aran = AU 10-ply. US Bulky = UK Chunky = AU 12-ply.
The biggest source of confusion is that UK 'double knitting' and US 'worsted' are not the same weight. UK DK is thinner than US worsted. Check the gauge range on the label to be sure.
How to Identify Unlabeled Yarn
If you have yarn without a label (from a destash, thrift store, or grandmother's attic), use the wraps-per-inch method: wrap the yarn snugly around a ruler for one inch without overlapping or stretching. Count the wraps.
18+ wraps = lace or fingering. 14–18 = fingering to sport. 12–14 = sport to DK. 9–12 = DK to worsted. 7–9 = worsted to bulky. 5–7 = bulky to super bulky. Fewer than 5 = jumbo.
Our Yarn Weight Chart tool includes an interactive WPI guide that matches your measurement to the correct weight category, along with recommended needle/hook sizes.