Hook size converter
US patterns say "G-6", your hook says "4 mm", and grandma's old UK pattern says "8" — they're all the same hook. Pick a size to see its equivalents.
Convert a hook size
Full conversion chart
Metric (mm) is the most reliable — when in doubt, go by the millimetres stamped on the hook.
| Metric (mm) | US | Vintage UK (pre-metric) |
|---|---|---|
| 2 mm | — | 14 |
| 2.25 mm | B-1 | 13 |
| 2.5 mm | — | 12 |
| 2.75 mm | C-2 | — |
| 3 mm | — | 11 |
| 3.25 mm | D-3 | 10 |
| 3.5 mm | E-4 | 9 |
| 3.75 mm | F-5 | — |
| 4 mm | G-6 | 8 |
| 4.5 mm | 7 | 7 |
| 5 mm | H-8 | 6 |
| 5.5 mm | I-9 | 5 |
| 6 mm | J-10 | 4 |
| 6.5 mm | K-10½ | 3 |
| 7 mm | — | 2 |
| 8 mm | L-11 | 0 |
| 9 mm | M/N-13 | 00 |
| 10 mm | N/P-15 | 000 |
| 15 mm | P/Q | — |
| 19 mm | S | — |
| 25 mm | T/U/X | — |
Sizes follow the Craft Yarn Council standards. "Vintage UK" is the old pre-metric numbering — it runs backwards (smaller number = bigger hook) and only appears on older hooks and patterns; modern UK hooks are labelled in mm. The mm measurement always wins.