Crochet hooks and hook sizes
Crochet hooks are sized by shaft diameter in millimetres, which is the only universal measurement. US hooks add a letter and number, such as H-8 for 5 mm, and old UK hooks use a number scale that runs backwards. Choose the size from the yarn label, then adjust up or down to match gauge.
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| Metric | US | Old UK | Yarn weights |
|---|---|---|---|
| 2.25 mm | B-1 | 13 | #1 |
| 2.75 mm | C-2 | 12 | #1 |
| 3.25 mm | D-3 | 10 | #1 |
| 3.5 mm | E-4 | 9 | #1, #2 |
| 3.75 mm | F-5 | — | #2 |
| 4 mm | G-6 | 8 | #2 |
| 4.5 mm | 7 | 7 | #2, #3 |
| 5 mm | H-8 | 6 | #3 |
| 5.5 mm | I-9 | 5 | #3, #4 |
| 6 mm | J-10 | 4 | #4 |
| 6.5 mm | K-10½ | 3 | #4, #5 |
| 7 mm | — | 2 | #5 |
| 8 mm | L-11 | 0 | #5 |
| 9 mm | M/N-13 | 00 | #5, #6 |
| 10 mm | N/P-15 | 000 | #6 |
| 11.5 mm | P-16 | — | #6 |
| 12 mm | — | — | #6 |
| 15 mm | P/Q | — | #6, #7 |
| 16 mm | Q | — | #7 |
| 19 mm | S | — | #7 |
US B-1 · UK 13
2.25 mm hook
US C-2 · UK 12
2.75 mm hook
US D-3 · UK 10
3.25 mm hook
US E-4 · UK 9
3.5 mm hook
US F-5 · UK —
3.75 mm hook
US G-6 · UK 8
4 mm hook
US 7 · UK 7
4.5 mm hook
US H-8 · UK 6
5 mm hook
US I-9 · UK 5
5.5 mm hook
US J-10 · UK 4
6 mm hook
US K-10½ · UK 3
6.5 mm hook
US — · UK 2
7 mm hook
US L-11 · UK 0
8 mm hook
US M/N-13 · UK 00
9 mm hook
US N/P-15 · UK 000
10 mm hook
US P-16 · UK —
11.5 mm hook
US — · UK —
12 mm hook
US P/Q · UK —
15 mm hook
US Q · UK —
16 mm hook
US S · UK —
19 mm hook
What size crochet hook should you use?
Use the hook size printed on the yarn label as a starting point, then change hook size until your swatch matches the pattern gauge. A larger hook makes bigger, looser stitches; a smaller hook makes tighter ones.
Amigurumi usually uses a hook one or two sizes smaller than the label suggests so stuffing does not show through.
How do you choose the right crochet hook?
Choose the hook size from your yarn weight, then adjust until your gauge swatch matches the pattern: a larger hook makes looser, bigger stitches and a smaller hook makes tighter ones. Beyond size, hooks differ in material and shape. Aluminium hooks glide quickly and are inexpensive; ergonomic handles reduce hand strain on long projects; wooden and bamboo hooks grip slippery yarn; steel hooks are used for fine thread.
Hook heads are either inline, where the head is the same width as the shaft, or tapered. Neither is better — if stitches keep slipping off or splitting, try the other style. Every size page here lists its US and old UK equivalent and the yarn weights it suits.
Frequently asked questions
Does hook size matter in crochet?
Yes. Hook size controls stitch size, which controls the finished dimensions and how much yarn a project uses.