Textile Yarn Converter
Convert knitting needle and crochet hook sizes between US, UK/Canada, metric (mm) and Japanese systems, and look up Craft Yarn Council yarn-weight categories with their recommended gauge, needle and hook sizes.
Input
Pick what you want to convert — the equivalents update instantly.
Type a size from any system to find its equivalents.
Output
| Property | Value |
|---|---|
| No data yet | |
Guides
The Textile Yarn Converter translates knitting and crochet sizes between the different naming systems used around the world. Enter a knitting needle or crochet hook size in any system — US, UK/Canada, metric (mm) or Japanese — and instantly see every equivalent, or pick a yarn weight to see its Craft Yarn Council category with the recommended gauge, needle and hook sizes.
It runs entirely in your browser: no size charts to squint at, no uploads, nothing leaves your device.
What it converts
- Knitting needles — convert between US numbers, UK/Canada numbers, metric millimetres and Japanese sizes. Enter a size in whichever system your pattern or needle uses and read across to the rest.
- Crochet hooks — convert between US letter/number labels (B-1, C-2, H-8, …), UK/Canada numbers and metric millimetres.
- Yarn weight — look up any of the eight Craft Yarn Council categories (0 Lace through 7 Jumbo), with its common names (Fingering, DK, Worsted, Aran, Bulky…), wraps-per-inch, knit and crochet gauge, and the recommended needle and hook range.
How to use it
- Choose What to convert: Knitting Needle, Crochet Hook, or Yarn Weight.
- For needles and hooks, type a Size and pick the System that size belongs to. For yarn, just choose a Yarn weight.
- The Result line and the Equivalents table update instantly. Copy the result or download the table as CSV.
Metric input is flexible — 4.5, 4,5, 4.5 mm and 4.5mm are all understood, and the nearest charted size within 0.15 mm is matched if you enter an in-between value.
Why do UK and US needle numbers run opposite ways?
UK/Canada needle numbering is descending: a bigger UK number means a smaller needle (UK 14 is 2 mm, UK 000 is 10 mm). US numbering ascends like metric — a bigger number is a bigger needle. That reversal is exactly why a converter helps: eyeballing the two systems side by side is genuinely confusing. Metric millimetres are the only unambiguous reference, which is why every equivalent here is anchored to the mm value.
What is WPI and why does it matter?
WPI, or wraps per inch, is the most reliable way to identify an unlabelled yarn. Wrap the yarn snugly around a ruler for one inch and count the wraps — more wraps means a finer yarn. The yarn-weight table lists the typical WPI for each category so you can match a mystery skein to a standard weight, then read off the recommended needle and hook sizes.
Are the yarn weights a global standard?
The Craft Yarn Council's 0–7 categories are the closest thing to a global standard, and most modern yarn labels print the matching symbol. Older or hand-dyed yarns may not, which is where WPI and gauge come in. Crochet hooks in particular have no single worldwide standard, so brands vary slightly — treat the letter/number labels as a close guide rather than an exact rule.
All conversions are based on published Craft Yarn Council standards and the standard US/UK/Japanese needle and hook charts.