There are several thicknesses of yarn, also referred to as weight. This is not to be confused with the measurement of weight listed above. The Craft Yarn Council of America is making an effort to promote a standardized industry system for measuring this, numbering the weights from 1 (finest) to 6 (heaviest)[4]. Some of the names for the various weights of yarn from finest to thickest are called lace, fingering, sock, sport, double-knit (or DK), worsted, aran, bulky, and super-bulky. This naming convention is more descriptive than precise; fiber artists disagree about where on the continuum each lies, and the precise relationships between the sizes.
A more precise measurement of yarn weight, often used by weavers, is wraps per inch (wpi). The yarn is wrapped snugly around a ruler and the number of wraps that fit in an inch are counted.
Labels on yarn for handcrafts often include information on gauge, known in the UK as tension, which is a measurement of how many stitches and rows are produced per inch or per centimeter on a specified size of knitting needle or crochet hook. The proposed standardization uses a four-by-four inch/ten-by-ten centimeter knitted or crocheted square, with the resultant number of stitches across and rows high made by the suggested tools on the label to determine the gauge.
Wraps per inch (WPI)
One way of determining the weight of an unknown yarn is to use the wrapping method.Wrap the yarn around a large needle or a ruler. Make sure the yarn lies flat. Push the yarn together so there are no gaps between wraps. Smooth it out so it is neither too loose nor too tight. Measure the number of wraps per inch (2.5 cm). For better accuracy, measure the wraps at the centre of your yarn sample.
| Standard Yarn Weight System | Yarn Type (US) | Ply (UK, NZ, AU)[2] | Wraps Per Inch (WPI)[2] |
|---|---|---|---|
| 0 or Lace | Thread, Cobweb and Lace | 1 - 3 ply | 18+ wpi |
| 1 or Superfine | Fingering | 4 ply | 14 wpi |
| 2 or Fine | Sport | 5 ply | 12 wpi |
| 3 or Light | DK | 8 ply | 11 wpi |
| 4 or Medium | Worsted | 10 ply | 9 wpi |
| 4 or Medium | Aran | 10 ply | 8 wpi |
| 5 or Bulky | Bulky | 12 ply | 7 wpi |
| 6 or Super Bulky | Super Bulky | 5-6 wpi |
International yarn weight conversion
| USA | UK | Australia | Suggested needle (mm) |
|---|---|---|---|
| Laceweight | 2ply | 2ply | 1.5–2.25 mm |
| Light Fingering | 3ply | 3ply | 2.25– 3 mm |
| Fingering | Sock | 4ply | 2.25— 3.25 mm |
| Sport | Light DK | 5ply | 3.25— 3.75 mm |
| DK/Light Worsted | DK | 8ply | 3.75— 4.5 mm |
| Worsted | No equivalent, suggest Aran | 4.5— 5.5 mm | |
| Aran | Aran | 4.5— 5.5 mm | |
| Bulky | Chunky | 12 ply | 5.5– 8 mm |
| Super Bulky | Super Chunky | 8 mm and up |
Standard Yarn Weight System
Categories of yarn, gauge ranges, and recommended needle and hook sizes
Yarn Weight Symbol & Category Names |  |  |  |  |  |  |  |
|---|---|---|---|---|---|---|---|
Type of Yarns in Category | Fingering 10-count crochet thread | Sock, Fingering, Baby | Sport, Baby | DK, Light Worsted | Worsted, Afghan, Aran | Chunky, Craft, Rug | Bulky, Roving |
Knit Gauge Range* in Stockinette Stitch to 4 inches | 33–40** sts | 27–32 sts | 23–26 sts | 21–24 st | 16–20 sts | 12–15 sts | 6–11 sts |
Recommended Needle in Metric Size Range | 1.5–2.25 mm | 2.25— 3.25 mm | 3.25— 3.75 mm | 3.75— 4.5 mm | 4.5— 5.5 mm | 5.5— 8 mm | 8 mm and larger |
Recommended Needle U.S. Size Range | 000–1 | 1 to 3 | 3 to 5 | 5 to 7 | 7 to 9 | 9 to 11 | 11 and larger |
Crochet Gauge* Ranges in Single Crochet to 4 inch | 32–42 double crochets** | 21–32 sts | 16–20 sts | 12–17 sts | 11–14 sts | 8–11 sts | 5–9 sts |
Recommended Hook in Metric Size Range | Steel*** 1.6–1.4 mm | 2.25— 3.5 mm | 3.5— 4.5 mm | 4.5— 5.5 mm | 5.5— 6.5 mm | 6.5— 9 mm | 9 mm and larger |
Recommended Hook U.S. Size Range | Steel*** 6, 7, 8 Regular hook B–1 | B–1 to E–4 | E–4 to 7 | 7 to I–9 | I–9 to K–10 1⁄2 | K–10 1⁄2 to M–13 | M–13 and larger |
| * GUIDELINES ONLY: The above reflect the most commonly used gauges and needle or hook sizes for specific yarn categories. ** Lace weight yarns are usually knitted or crocheted on larger needles and hooks to create lacy, openwork patterns. Accordingly, a gauge range is difficult to determine. Always follow the gauge stated in your pattern. *** Steel crochet hooks are sized differently from regular hooks—the higher the number, the smaller the hook, which is the reverse of regular hook sizing | |||||||
