Knitting needle & crochet hook size converter
Convert any knitting needle or crochet hook size between metric, US and old UK sizes, and see which yarn weights it suits.
Updated
Reference charts
Full tables to check sizes, yarn weights and pattern abbreviations mid-project.
- Knitting needle size chart
Metric, US and UK needle sizes side by side. - Crochet hook size chart
Metric, US letter and UK hook sizes. - Yarn weight chart
Lace to jumbo: gauge, needle and hook sizes, WPI. - Knitting abbreviations
Searchable list, from alt to yo. - Crochet abbreviations
Searchable list with UK equivalents. - US vs UK crochet terms
Why a UK double crochet is a US single crochet.
Which size should I use?
Start with the size on the yarn's ball band or in your pattern, then knit or crochet a swatch. If you get more stitches per 10 cm (4 in) than the pattern, go up a size. If you get fewer, go down a size.
Common questions
Why do some sizes have no US or UK equivalent?
US and old UK sizes are numbers or letters, not measurements, and they skip some metric sizes. A 3.5 mm needle, for example, has no old UK number. Metric is the only system that covers every size, so use the mm size when you can.
Are UK and Canadian needle sizes the same?
Yes. The old UK and Canadian systems used the same numbers, where bigger numbers mean thinner needles. Both countries now mostly use metric.
Do US needle and hook numbers match?
Mostly, yes. From US 1 (2.25 mm) to US 15 (10 mm), a needle and a hook with the same US number are the same metric size. Hooks add a letter, so a US 6 needle and a G-6 hook are both 4 mm. Above 10 mm the two systems drift apart, so check the mm size.