Knitting & Crochet Sizes
Needle & hook: US, UK, mm.
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About Knitting & Crochet Sizes
Convert knitting needle and crochet hook sizes between US, UK/Canadian and metric (mm). Switch between needles and hooks, pick a size in any system, and see the equivalents — with a full conversion chart below.
Millimetres are the reliable reference: where a system has no exact match the tool says so, instead of forcing a wrong size. It is completely free with no sign-up, and it runs entirely in your browser.
Frequently asked questions
- What size is a US 8 knitting needle in mm and UK?
- A US 8 knitting needle is 5.0 mm, which is a UK/Canadian size 6. Pick any system in the tool to see the other two.
- What is a US G/6 crochet hook in millimetres?
- A US G/6 crochet hook is 4.0 mm (UK/Canadian size 8). US crochet hooks carry both a letter and a number, and this tool shows both.
- Why does the UK/Canadian scale run backwards?
- It's an old wire-gauge numbering, so a higher UK number means a thinner needle or hook — the opposite of the millimetre and US scales. That's why converting through millimetres is the reliable way.
- Why do some sizes show a dash?
- A dash means there's genuinely no exact equivalent in that system for that millimetre size — for example 3.0 mm has a UK size but no standard US number. In that case, pick the nearest millimetre size instead of forcing a match.
- Are US crochet hook letters exact?
- They vary slightly between manufacturers (an E/4 may be 3.5 mm or 3.75 mm, for instance), so the millimetre value is the one to trust. Steel/thread hooks use a separate reversed scale and aren't included here.
- What do yarn weights like DK, worsted and 4-ply mean?
- They describe yarn thickness. The Craft Yarn Council numbers them 0 (lace) to 7 (jumbo): fingering/sock is 1, DK (UK 8-ply) is 3, and worsted/aran (10-ply) is 4. The yarn weight guide on this page lines up the US, UK/ply and numbered names with the needle sizes they suit.