Aran vs worsted
Both are "medium" on the Craft Yarn Council scale, and most of the time they are interchangeable. The difference is at the edges. Worsted is the American name, and a typical worsted knits at 20 stitches to 4" on a US 7 or 8. Aran is the British name — from the Aran Islands' fisherman sweaters — and it is the heavier end of the same class: 18 stitches to 4" on a US 8 or 9. Some mills and shops call that end "heavy worsted".
So a British aran pattern will usually knit to gauge in an American worsted one needle size up, and an American worsted pattern in a British aran one size down — but a stitch an inch over a sweater is a size, so swatch. If the pattern's gauge is 18 stitches, start with yarns that say aran or heavy worsted on the band; if it is 20, start with worsted. Our worsted shelf holds both, and each line's gauge is on its page.
The ply names
In Britain, Australia and New Zealand, yarn weight is named by a number of plies: 4 ply, 8 ply and so on. The name is old enough that it was once literally the count of strands twisted together, but today it is only a thickness. A modern "4 ply" can be two plies or six; a single-ply yarn can be sold as 8 ply. Treat the number as a weight name, not a construction, and match the gauge.
| Ply name | American weight | Stitches per 4" | Also called |
|---|---|---|---|
| 2 ply | Lace | 32–40+ | cobweb, laceweight |
| 3 ply | Light fingering | 30–32 | |
| 4 ply | Fingering | 27–32 | sock, super fine |
| 5 ply | Sport | 24–26 | fine |
| 8 ply | DK | 21–24 | double knitting, light worsted |
| 10 ply | Worsted / aran | 16–20 | medium |
| 12 ply | Chunky | 12–15 | British "chunky" |
| 14 ply and up | Bulky / super bulky | 6–11 | British "super chunky" |
Two more British words trip people up. "Double knitting" is DK, not a technique and not a doubled yarn. And British "chunky" runs a little lighter than American bulky — the band's gauge settles it.
Ply as a construction
When a yarn's page here says "plied" or "single-ply", it means the construction — how many strands were twisted together — not the weight. Malabrigo Rios and Malabrigo Worsted are both worsted weight; Rios is plied and Worsted is a single, and the single-ply vs plied guide is about why that matters.
Finding the yarn a pattern wants
A pattern that says 4 ply wants a fingering yarn: on our shelves that is West Yorkshire Spinners Signature 4ply, which is literally named for it, Zauberball Crazy, Dream in Color Jilly and the rest of the fingering shelf. 8 ply or DK is the DK shelf — Schoppel Edition 3, Malabrigo Arroyo, Juniper Moon Zooey. 10 ply, aran or worsted is the worsted shelf; for the heavier aran end look at Harborside Aran, Fleece Jacobs Aran, Lamb's Pride Worsted and Malabrigo Worsted, and for the lighter worsted end at Rios and Nature Spun Worsted. 12 ply is chunky: Álafoss Lopi, Plymouth Baby Alpaca Grande, Araucania Jaspeada.
Whatever the name, the pattern's gauge is the number to match. The yarn weights guide has the whole scale with needle sizes and typical yardage.