Knitting needle and crochet hook size converter
Convert knitting needle and crochet hook sizes between metric (mm), American (US) and British (UK) systems.
Knitting needles and crochet hooks are graduated in millimetres in the metric system, but US and UK patterns use numbers that do not match directly. A 4 mm needle = US 6 = UK 8 in knitting. Crochet uses letters (G/6 = 4 mm).
Needle size directly affects gauge (number of stitches per 10 cm). To match a pattern, use exactly the recommended size and knit a swatch. If you knit tight, go up a half size; if you knit loose, go down a half size.
Full table — Knitting needles
| mm | US | UK / Canadian |
|---|---|---|
| 2 | 0 | 14 |
| 2.25 | 1 | 13 |
| 2.5 | 1.5 | 12 |
| 2.75 | 2 | 12 |
| 3 | 2.5 | 11 |
| 3.25 | 3 | 10 |
| 3.5 | 4 | — |
| 3.75 | 5 | 9 |
| 4 | 6 | 8 |
| 4.5 | 7 | 7 |
| 5 | 8 | 6 |
| 5.5 | 9 | 5 |
| 6 | 10 | 4 |
| 6.5 | 10.5 | 3 |
| 7 | 10.75 | 2 |
| 8 | 11 | 0 |
| 9 | 13 | 00 |
| 10 | 15 | 000 |
| 12 | 17 | — |
| 15 | 19 | — |
| 19 | 35 | — |
| 25 | 50 | — |
Frequently asked questions
Why do US and UK patterns use different numbers?
Historically, UK and US makers used numbering independent of metric. UK used the inverse of mm (smaller number = larger needle), US used an increasing scale. Mm has become the international reference.
How do I tell an unmarked needle size?
Use a needle gauge: a board with calibrated holes. The needle fits in the hole matching its size. Otherwise, measure the diameter with calipers, or compare visually to a known needle.
What size for a beginner?
Knitting beginners: 5 to 6 mm (big enough to see stitches, not so big as to lose precision). With medium or chunky yarn. Crochet beginners: 4 mm or 5 mm with sport or DK weight yarn.
Circular or straight needles?
Circulars are more versatile (flat or in the round) and more comfortable above 80 stitches. Straights remain simple for small projects. Many experienced knitters use only interchangeable circulars.