The complete guide to comparing yarn systems — convert Wraps Per Inch (WPI) to US weights, UK Ply, and recommended needle sizes.
Select by name or enter your WPI to get full needle & gauge data instantly.
| Category | US Weight | WPI Range | Gauge (4") | Recommended Needle | UK Term | Aus/NZ |
|---|---|---|---|---|---|---|
| Lace | 0 | 30-40+ | 33-40 sts | US 000-1 (1.5-2.25 mm) | Lace | 2 Ply |
| Super Fine | 1 | 14-30 | 27-32 sts | US 1-3 (2.25-3.25 mm) | 4 Ply | 4 Ply |
| Fine | 2 | 12-18 | 23-26 sts | US 3-6 (3.25-4.0 mm) | DK | 5 Ply |
| Light | 3 | 11-15 | 21-24 sts | US 6-8 (4.0-5.0 mm) | DK | 8 Ply |
| Medium | 4 | 9-12 | 16-20 sts | US 8-10 (5.0-6.0 mm) | Aran | 10 Ply |
| Bulky | 5 | 6-9 | 12-15 sts | US 10-13 (6.0-9.0 mm) | Chunky | 12 Ply |
| Super Bulky | 6 | 5-6 | 7-11 sts | US 13-19 (9.0-16.0 mm) | Super Chunky | 14 Ply |
Yarn labels are notoriously inconsistent. "Worsted" on the ball band is a starting point, not a guarantee. Different manufacturers, fibers, and dye lots can cause the same labelled weight to knit up at wildly different gauges. Furthermore, UK/Australian patterns use "Ply" while US patterns use standard numbers (0-6). Our calculator bridges these gaps. By measuring your Wraps Per Inch (WPI), you bypass label ambiguity entirely and find out exactly what thickness your yarn truly is.
The US Name: If you have a yarn label that specifies a US weight category (e.g., "Medium / Worsted").
Or a WPI Measurement: A pencil, a ruler, and your mystery yarn. Wrap the yarn side-by-side (touching but not overlapping) around the pencil for exactly one inch, and count the wraps.
Select "Convert by Name" if you know the US label weight, or "Find by WPI" if you just measured a mystery yarn.
Pick the weight from the dropdown menu, or type in your WPI number (e.g., 14) and click "Find Weight."
Instantly view the cross-regional translations (like UK/AUS Ply) and the standard recommended needle sizes to use with this yarn.
When you discover the standard category (e.g., 4-Medium) or the UK equivalent (e.g., 10-Ply), you can now safely substitute this yarn into any pattern that calls for those categories. The recommended needle size provides the perfect starting point for your gauge swatch.
Scenario: You lost the label for a beautiful skein in your stash and want to find a sweater pattern for it.
Input: You wrap the yarn around a pencil and count exactly 14 wraps in one inch. Enter "14" into the WPI tool.
Conversion Math: The tool locates 14 WPI within the standard classification bounds.
Result: Super Fine (Fingering) / UK 4-Ply. You should look for patterns requiring Fingering weight yarn and start swatching with a US 1-3 (2.25-3.25 mm) needle.
Yes, fiber content affects how a yarn sits. Wool's elasticity allows a slightly looser wrap with natural bounce-back, while cotton and linen are inelastic and tend to wrap tighter for the same physical thickness. Always wrap with "natural" tension—don't stretch the yarn tight against the pencil.
In the UK, Australia, and New Zealand, "Ply" evolved into a weight category rather than a literal strand count. Historically, a standard thickness of yarn was spun and plied together. 8 strands (8-ply) created what we now call "DK" or "Light" weight. Today, an 8-ply yarn might technically be a single roving strand, but it retains the "8 Ply" name to denote its DK thickness.
No. DK (Double Knitting) is a Light weight (Category 3), whereas Worsted is a Medium weight (Category 4). Substituting one for the other will drastically alter the size and drape of your finished garment unless you make significant mathematical adjustments to your stitch counts.