Knitting & Crochet Sizes
Needle & hook: US, UK, mm.
Needle & hook: US, UK, mm.
How to use Knitting & Crochet Sizes
- Switch between knitting needles and crochet hooks
- Pick a size in US, UK/Canadian, or metric millimetres
- Read the equivalents, using the full chart for exact matches
About Knitting & Crochet Sizes
This converter turns any knitting needle or crochet hook size into its US, UK/Canadian and metric (mm) equivalents. Pick whether you're working with needles or hooks, choose a size in whichever system your pattern uses, and the other two fill in instantly — so a US 8 needle shows as 5.0 mm and UK 6, or a US G/6 crochet hook shows as 4.0 mm and UK 8. A full conversion chart sits below the tool if you'd rather scan every size at once.
Millimetres are the anchor here, because that's the one measurement that doesn't drift. The UK/Canadian scale runs backwards on an old wire-gauge system (a higher number means a thinner needle or hook), and US crochet hook letters vary a little between brands, so converting through mm is what keeps you honest. Where a system genuinely has no matching size, the tool shows a dash instead of inventing one, and you can drop to the nearest millimetre instead.
There's also a yarn weight guide that lines up names like lace, fingering/sock, DK (8-ply), worsted and aran (10-ply) with the Craft Yarn Council's 0–7 numbers and the needle sizes each one suits, so you can match a tool to your yarn. Everything is completely free with no sign-up, and it runs entirely in your browser — nothing you enter is uploaded.
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.
- How do I convert a crochet hook size?
- Switch the tool to crochet hooks, then pick your size in US letter/number, UK/Canadian or millimetres, and it shows the matching sizes in the other two systems. For example, a US H/8 hook is 5.0 mm. The chart below lists every hook size side by side.
- How do I convert a US knitting needle size to mm?
- Set the tool to needles and choose the US number to read off the millimetre value — a US 6 is 4.0 mm and a US 10 is 6.0 mm. Because mm is the actual measurement, it's the safest figure to follow when a pattern from another country lists needles differently.
- What is a UK knitting needle size in US?
- Because the UK/Canadian scale is reversed, a UK 8 is a US 6 (4.0 mm) and a UK 6 is a US 8 (5.0 mm). Pick the UK size in the tool and it fills in the US and metric equivalents so you don't have to count backwards yourself.
- Does this convert both knitting needles and crochet hooks?
- Yes. You can switch between needles and hooks, each with its own size scale, so you can look up either one without mixing the two up. The conversion chart also keeps separate needle and hook listings.
- 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.
- Is there a full needle and hook conversion chart?
- Yes, a complete chart appears under the converter listing US, UK/Canadian and metric sizes together for both needles and hooks. It's useful for a quick scan when you're substituting tools for a pattern.
- Is the converter free and private?
- Yes, it's completely free with no sign-up or install, and it runs entirely in your browser. Nothing you type is sent to a server.