Yarn Weight Guide
Complete reference for all yarn weights — needle sizes, hook sizes, gauge ranges, WPI, and project ideas. Includes WPI identifier and needle size converter.
| US Size | Metric (mm) | UK / Old UK | Common yarn weight |
|---|---|---|---|
| 000 | 1.5 mm | — | Lace |
| 00 | 1.75 mm | — | Lace |
| 0 | 2.0 mm | 14 | Lace / Fingering |
| 1 | 2.25 mm | 13 | Fingering |
| 1.5 | 2.5 mm | 12 | Fingering |
| 2 | 2.75 mm | 12 | Fingering / Sport |
| 3 | 3.25 mm | 10 | Sport |
| 4 | 3.5 mm | — | Sport / DK |
| 5 | 3.75 mm | 9 | DK |
| 6 | 4.0 mm | 8 | DK / Worsted |
| 7 | 4.5 mm | 7 | Worsted |
| 8 | 5.0 mm | 6 | Worsted |
| 9 | 5.5 mm | 5 | Worsted / Bulky |
| 10 | 6.0 mm | 4 | Bulky |
| 10.5 | 6.5 mm | 3 | Bulky |
| 11 | 8.0 mm | 0 | Super Bulky |
| 13 | 9.0 mm | 00 | Super Bulky |
| 15 | 10.0 mm | 000 | Super Bulky / Jumbo |
| 17 | 12.0 mm | — | Jumbo |
| 19 | 15.0 mm | — | Jumbo |
| 35 | 19.0 mm | — | Jumbo |
| 50 | 25.0 mm | — | Jumbo |
How to Measure WPI
Wrap yarn around a ruler or pencil snugly but not tightly — each wrap should touch the next without overlapping or squishing. Count how many wraps fit in one inch. That number is your Wraps Per Inch (WPI). Higher WPI means thinner yarn. A lace-weight yarn might have 30–40 WPI while a super bulky might have only 4–6 WPI.
Substituting Yarn Weights
The safest yarn substitution is within the same weight category. Replace a DK with another DK and swatch carefully — even two DK yarns can have different gauges due to fiber content, twist, and construction. Substituting one weight category up or down (e.g., DK for Sport) requires using this resizer to recalculate stitch counts. Substituting two or more weight categories changes the fabric character so significantly that only the finished measurements from the pattern are usable.
Fiber Affects Gauge
Beyond weight, fiber content changes how yarn behaves. Wool is elastic and springs back, giving crisp stitch definition. Cotton is inelastic, which makes gauge harder to maintain and can cause hand fatigue. Acrylic is consistent and easy to care for but can feel stiff. Silk blends are drapey. Matching both fiber content and weight gives the closest substitution result.