Stitch n Pattern — https://stitchnpattern.com/reference/crochet-hook-size-chart.html
Reference
Crochet Hook Size Chart
US hooks are labeled with a letter and a number, which don't always move in lockstep - this table lines up the letter/number sizing against the metric millimeter size that stays consistent across every hook you own.
Last updated August 3, 2026
| Metric (mm) | US Size | UK / Old Size |
|---|---|---|
| 2.25 mm | B-1 | 13 |
| 2.75 mm | C-2 | 12 |
| 3.25 mm | D-3 | 10 |
| 3.5 mm | E-4 | 9 |
| 3.75 mm | F-5 | 8 |
| 4.0 mm | G-6 | 8 |
| 4.5 mm | 7 | 7 |
| 5.0 mm | H-8 | 6 |
| 5.5 mm | I-9 | 5 |
| 6.0 mm | J-10 | 4 |
| 6.5 mm | K-10½ | 3 |
| 8.0 mm | L-11 | 0 |
| 9.0 mm | M/N-13 | 00 |
| 10.0 mm | N/P-15 | 000 |
| 15.0 mm | P/Q | — |
| 16.0 mm | Q | — |
| 19.0 mm | S | — |
Steel hooks used for thread crochet have their own, separate size range (typically 00 down to 16, running opposite to regular hook sizing) and aren't included in this table.