Crochet hooks – particularly antique hooks – can be made of many different materials: bone, brass, horn, ivory, mother of peral, pewter, silver, tortoise shell and different types of wood. Modern hooks are commonly made of metal, plastic or wood.
The diameter of the shaft of a crochet hook determines the size of the stitch since the loop is formed around the shaft. The size of your hook determines the size of yarn you can use. Hooks are divided into 2 groups: yarn hooks and steel (thread) hooks. Yarn hooks are made of aluminum, plastic or wood. Generally, these are used for larger diameter yarns. Steel hooks, or thread hooks as they are also called, are made of steel and are used for thread.
Yarn hook sizes are given either metric sizes (2.25 – 15.00mm); letters (B-Q, with B being the smallest); and sometimes by number (B=1 or 2, etc.) Your hook will be stamped with any of these sizes.
Steel hooks range from size 14 (= .75mm) to size 00 (= 3.5mm). When comparing steel hooks with yarn hooks, they’ll overlap in the 2.25 – 3.50 mm range.
| Yarn Hooks | Steel Hooks |
| B (2.25mm) | 14 (0.75mm) |
| C (2.75mm) | 13 (0.85mm) |
| D (3.25mm) | 12 (1.00mm) |
| E (3.50mm) | 11 (1.10mm) |
| F (3.75mm) | 10 (1.30mm) |
| G (4.00mm) | 9 (1.40mm) |
| H (5.00mm) | 8 (1.50mm) |
| I (5.50mm) | 7 (1.65mm) |
| J (6.00mm) | 6 (1.80mm) |
| K (6.50mm) | 5 (1.90mm) |
| N (9.00mm) | 4 (2.00mm) |
| P (10.00mm) | 3 (2.10mm) |
| Q (15.00mm) | 2 (2.25mm) |
| 1 (2.75mm) | |
| 0 (3.25mm) | |
| 00 (3.50mm) |
