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Yarn Weight Conversion Calculator
Convert between US, UK, and Australian yarn weight names, wraps per inch (WPI), gauge, and needle/hook sizes — so you can substitute yarn with confidence.
Convert a yarn weight
Pick a weight to see every equivalent at once.
CYCA 0
Lace / Fingering (10-count crochet thread) / Cobweb / Thread
UK name
2 Ply / Lace
Australian name
2 Ply
WPI (approx.)
35+
Knit gauge (4in / 10cm)
33–40 sts
Knit needle
1.5–2.25 mm · US 000–1
Crochet gauge (4in / 10cm)
32–42 sts
Crochet hook
1.4–2.25 mm · US Steel 6–8 / B-1
CYCA 1
Super Fine / Sock / Fingering / Baby
UK name
3–4 Ply
Australian name
4 Ply
WPI (approx.)
14–30
Knit gauge (4in / 10cm)
27–32 sts
Knit needle
2.25–3.25 mm · US 1–3
Crochet gauge (4in / 10cm)
21–32 sts
Crochet hook
2.25–3.5 mm · US B-1–E-4
CYCA 2
Fine / Sport / Baby
UK name
5 Ply
Australian name
5 Ply
WPI (approx.)
12–18
Knit gauge (4in / 10cm)
23–26 sts
Knit needle
3.25–3.75 mm · US 3–5
Crochet gauge (4in / 10cm)
16–20 sts
Crochet hook
3.5–4.5 mm · US E-4–7
CYCA 3
Light / DK / Light Worsted
UK name
DK (Double Knit)
Australian name
8 Ply
WPI (approx.)
11–15
Knit gauge (4in / 10cm)
21–24 sts
Knit needle
3.75–4.5 mm · US 5–7
Crochet gauge (4in / 10cm)
12–17 sts
Crochet hook
4.5–5.5 mm · US 7–I-9
CYCA 4
Medium / Worsted / Afghan / Aran
UK name
Aran
Australian name
10 Ply
WPI (approx.)
9–12
Knit gauge (4in / 10cm)
16–20 sts
Knit needle
4.5–5.5 mm · US 7–9
Crochet gauge (4in / 10cm)
11–14 sts
Crochet hook
5.5–6.5 mm · US I-9–K-10.5
CYCA 5
Bulky / Chunky / Craft / Rug
UK name
Chunky
Australian name
12 Ply
WPI (approx.)
7–9
Knit gauge (4in / 10cm)
12–15 sts
Knit needle
5.5–8 mm · US 9–11
Crochet gauge (4in / 10cm)
8–11 sts
Crochet hook
6.5–9 mm · US K-10.5–M-13
CYCA 6
Super Bulky / Super Chunky / Roving
UK name
Super Chunky
Australian name
14 Ply
WPI (approx.)
5–7
Knit gauge (4in / 10cm)
7–11 sts
Knit needle
8–12.75 mm · US 11–17
Crochet gauge (4in / 10cm)
5–9 sts
Crochet hook
9–15 mm · US M-13–Q
CYCA 7
Jumbo / Roving
UK name
Jumbo
Australian name
16 Ply+
WPI (approx.)
under 5
Knit gauge (4in / 10cm)
6 sts or fewer
Knit needle
12.75 mm+ · US 17+
Crochet gauge (4in / 10cm)
4 sts or fewer
Crochet hook
15 mm+ · US Q+
Full yarn weight conversion chart
Every category at once — useful for comparing across a whole pattern.
| CYCA | US name | UK | Australian | WPI | Knit needle | Crochet hook |
|---|---|---|---|---|---|---|
| 0 | Lace | 2 Ply / Lace | 2 Ply | 35+ | 1.5–2.25 mm · US 000–1 | 1.4–2.25 mm · US Steel 6–8 / B-1 |
| 1 | Super Fine | 3–4 Ply | 4 Ply | 14–30 | 2.25–3.25 mm · US 1–3 | 2.25–3.5 mm · US B-1–E-4 |
| 2 | Fine | 5 Ply | 5 Ply | 12–18 | 3.25–3.75 mm · US 3–5 | 3.5–4.5 mm · US E-4–7 |
| 3 | Light | DK (Double Knit) | 8 Ply | 11–15 | 3.75–4.5 mm · US 5–7 | 4.5–5.5 mm · US 7–I-9 |
| 4 | Medium | Aran | 10 Ply | 9–12 | 4.5–5.5 mm · US 7–9 | 5.5–6.5 mm · US I-9–K-10.5 |
| 5 | Bulky | Chunky | 12 Ply | 7–9 | 5.5–8 mm · US 9–11 | 6.5–9 mm · US K-10.5–M-13 |
| 6 | Super Bulky | Super Chunky | 14 Ply | 5–7 | 8–12.75 mm · US 11–17 | 9–15 mm · US M-13–Q |
| 7 | Jumbo | Jumbo | 16 Ply+ | under 5 | 12.75 mm+ · US 17+ | 15 mm+ · US Q+ |
Crochet thread numbering to yarn weight
Thread sizes (like DMC or Lizbeth) run opposite to yarn weight — the bigger the number, the finer the thread. Size 10 is the Craft Yarn Council's own reference point for Lace weight; the rest of this table is a commonly used approximation, since there's no official CYCA table for thread sizes.
| Thread size | Closest yarn weight (CYCA) | Note |
|---|---|---|
| Size 3 | 2–3 (Fine–Light) | Thicker crochet thread |
| Size 5 | 1 (Super Fine) | Medium crochet thread |
| Size 8 | 0–1 (Lace–Super Fine) | Fine crochet thread |
| Size 10 | 0 (Lace) | CYCA's own reference point for Lace weightCYCA reference point |
| Size 20 | 0 (fine Lace) | Finer than standard lace |
| Size 30 | 0 (extra-fine Lace) | Extra-fine lace/thread |
| Size 40–80 | 0 (finest) | Tatting / fine lacemaking thread |
Substituting a different yarn
Swapping in a yarn the pattern didn't call for? Two things change: hook/needle size, and how much yarn you need.
Hook / needle size
Match gauge, not just the weight name — brands vary. Start with the range for your yarn's CYCA category in theconverter above, then swatch. Getting more stitches per inch than the pattern wants? Go up a size. Fewer? Go down a size.
Yardage calculator
Find "yards per 100g" (or per skein) on both yarn labels, then work out how much of the substitute yarn you'll actually need.
Method: convert the pattern's yardage to weight using your original yarn's yards-per-100g, then convert that weight to yardage using the substitute yarn's yards-per-100g. This is the standard weight-based substitution method used across the yarn industry — it assumes similar fiber density, so still swatch to confirm gauge.
Frequently asked questions
What is the Standard Yarn Weight System?
It's a numbered system (0 Lace through 7 Jumbo) published by the Craft Yarn Council to give every yarn a consistent weight category, with matching gauge ranges and recommended needle/hook sizes. Most yarn labels show this number inside a small skein icon.
What does WPI mean, and how do I measure it?
WPI is "wraps per inch" — wrap a length of yarn snugly (not stretched) around a ruler or WPI tool for one inch and count the wraps. It's a quick way to identify an unlabeled yarn's weight when you don't have the ball band. WPI ranges by category are a widely used approximation, not an official Craft Yarn Council figure.
How do US, UK, and Australian yarn weight names compare?
They describe roughly the same thickness categories but use different names and, for UK/AU, a "ply" count (e.g. US Worsted ≈ UK Aran ≈ AU 10 Ply). These regional equivalents are commonly used conventions, not a single official standard, and exact gauge still varies by brand — always check the ball band gauge if it's available.
What's the difference between yarn weight and crochet thread size?
Crochet thread (like DMC or Lizbeth) uses a separate numbering system where a higher number means a finer thread — the opposite direction from yarn weight numbers. The Craft Yarn Council anchors one point on this scale directly: Size 10 crochet thread sits inside the Lace (CYCA 0) category. Finer or thicker thread sizes beyond that are matched to yarn weight by community convention.
Can I substitute a different weight yarn than the pattern calls for?
Yes, but match gauge, not just the weight name — swatch first. You'll also need to recalculate how much yarn to buy: convert the pattern's yardage to a weight using your original yarn's yards-per-100g, then back to yardage using the substitute yarn's yards-per-100g. The calculator on this page does that conversion for you.
Are the numbers on this site official standards?
The CYCA category numbers, gauge ranges, and needle/hook sizes come directly from the Craft Yarn Council's published Standard Yarn Weight System. WPI ranges, UK/AU name equivalents, and the thread-numbering table are commonly used approximations from the fiber crafting community — we label these separately so you always know which is which.