Free Crochet Craft Tools & Calculators
Interactive calculators, row counters, size converters, and planning tools engineered specifically for yarn crafters. 100% offline-ready.
Yarn Weight Converter
Standard Yarn Weight Converter (CYC 0-7)
Convert between CYC categories, Wraps Per Inch (WPI), ply ratings, and hook sizes.
Standard Yarn Weight Converter — CYC 0-7 Standards, WPI & Ply Guide
Master Craft Yarn Council classifications, Wraps Per Inch (WPI) testing, and international ply conversions.
Standard Yarn Weight Chart (CYC 0-7), WPI & Ply Conversion
Understanding yarn weight categories is critical when substituting yarns or adapting international patterns. This interactive yarn weight converter maps Craft Yarn Council (CYC) standards (0 Lace to 7 Jumbo) to Wraps Per Inch (WPI), traditional UK/Australian ply ratings, recommended crochet hook sizes, and knitting needle gauges.
Master Yarn Weight & WPI Conversion Table
| CYC Category | Standard US Names | UK / AU Ply | WPI (Wraps Per Inch) | Recommended Hook | Recommended Needles |
|---|---|---|---|---|---|
| #0 Lace | Fingering 10-count, Thread | 1-ply / 2-ply | 18+ WPI | 1.6 - 2.25 mm (Steel 6 to B-1) | 1.5 - 2.25 mm (US 000 - 1) |
| #1 Super Fine | Sock, Fingering, Baby | 3-ply / 4-ply | 14 - 18 WPI | 2.25 - 3.5 mm (B-1 to E-4) | 2.25 - 3.25 mm (US 1 - 3) |
| #2 Fine | Sport, Baby | 5-ply | 12 - 14 WPI | 3.5 - 4.5 mm (E-4 to 7) | 3.25 - 3.75 mm (US 3 - 5) |
| #3 Light | DK (Double Knitting), Light Worsted | 8-ply | 11 - 12 WPI | 4.5 - 5.5 mm (7 to I-9) | 3.75 - 4.5 mm (US 5 - 7) |
| #4 Medium | Worsted, Afghan, Aran | 10-ply / 12-ply | 9 - 11 WPI | 5.5 - 6.5 mm (I-9 to K-10.5) | 4.5 - 5.5 mm (US 7 - 9) |
| #5 Bulky | Chunky, Craft, Rug | 12-ply / 14-ply | 7 - 8 WPI | 6.5 - 9.0 mm (K-10.5 to M-13) | 5.5 - 8.0 mm (US 9 - 11) |
| #6 Super Bulky | Super Bulky, Roving | 16-ply+ | 5 - 6 WPI | 9.0 - 15.0 mm (M-13 to Q) | 8.0 - 12.75 mm (US 11 - 17) |
| #7 Jumbo | Jumbo, Arm Knitting Roving | Giant | 1 - 4 WPI | 15.0 mm+ (Q and larger) | 12.75 mm+ (US 17+) |
How to Measure WPI (Wraps Per Inch)
- Take a standard wooden pencil or ruler.
- Wrap your unidentified mystery yarn around the ruler so the strands sit snugly side by side without overlapping or stretching.
- Count how many wraps fit inside 1 inch (2.54 cm).
- Compare your count against the WPI column in the table above to identify the yarn category!
Frequently Asked Questions
Q: Can I hold two strands of DK yarn together to equal Worsted?
A: Holding two strands of #3 DK yarn together produces a gauge similar to #5 Bulky yarn. To match #4 Worsted weight, hold two strands of #2 Sport or #1 Fingering weight yarn together.
Q: What is the difference between Worsted and Aran weight?
A: Both are classified as #4 Medium weight, but Aran is slightly heavier (traditional 10-ply to 12-ply) with a denser drape than standard Worsted.