Yarn weights explained
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“Weight” in yarn does not mean how heavy the ball is. It means how thick the strand is. The confusion is that the US, the UK, and Australia and New Zealand each named those thicknesses differently, and the names do not line up neatly.
The three systems
United States. Descriptive names (lace, fingering, sport, DK, worsted, bulky, super bulky) alongside the Craft Yarn Council (CYC) numbering system, which runs from 0 (lace) to 7 (jumbo).
United Kingdom. Historically ply-based names, though UK usage has drifted toward the US names for the middle of the range. 4-ply and aran are still in common use.
Australia and New Zealand. Ply numbers throughout: 2-ply, 4-ply, 8-ply, 10-ply, 12-ply.
The critical thing to understand about ply numbers: they no longer describe how many strands are twisted together. An 8-ply yarn is not necessarily made of eight plies. The number survives as a thickness label only. A modern “8-ply” might be spun as three plies or as a single.
Rough equivalents
| CYC | US | UK | AU/NZ |
|---|---|---|---|
| 0 | Lace | 1-ply, 2-ply | 1-ply, 2-ply |
| 1 | Fingering, sock | 3-ply, 4-ply | 3-ply, 4-ply |
| 2 | Sport | 5-ply | 5-ply |
| 3 | DK | DK, 8-ply | 8-ply |
| 4 | Worsted | Aran, 10-ply | 10-ply |
| 5 | Bulky | Chunky | 12-ply |
| 6 | Super bulky | Super chunky | n/a |
| 7 | Jumbo | n/a | n/a |
Treat this as a starting point rather than a guarantee. The boundaries are genuinely fuzzy, and manufacturers do not apply them consistently. One brand’s DK is another’s light worsted.
Why gauge beats the label
The only reliable measure of a yarn is the gauge you personally get with it. Two yarns both labelled worsted can knit up noticeably differently depending on fibre, spin, and ply structure. A tightly spun worsted-weight cotton behaves nothing like a loosely spun worsted-weight single-ply wool.
If the pattern gives a gauge, swatch for it. The weight label tells you which yarns are worth swatching; it does not tell you which one will work.
How YarnHub handles this
Set your region once and every yarn weight in the app displays in your system. A yarn catalogued in the US as worsted shows as 10-ply to an Australian user and aran to a UK user, without anyone re-entering data.
Where a yarn’s CYC number is known, it appears on the weight badge, for example CYC3 · DK, so you have the unambiguous number alongside the regional name.