crochet hook size guide
Crochet Hook Size Guide Chart of Metric vs US / UK / Canada Crochet Hook Sizes*:

Millimeter Size (mm)
Crochet Hook Size (US)
Crochet Hook Size (UK/CA)
2.0 mm 14
2.25 mm B-1 13
2.5 mm 12
2.75 mm C-2
3.0 mm 11
3.25 mm D-3 10
3.5 mm E-4 9
3.75 mm F-5
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-10.5 3
7.0 mm 2
7.5 mm 1
8.0 mm L-11 0
9.0 mm M-13 00
10.0 mm N-15 000
12 mm O-16
15.0 mm P/Q-19
15.75 / 16.0 mm Q
17.5 mm R
19.0 mm S-35
25.0 mm U

*Trust the millimeter (mm) size as the letter / number can vary by manufacturer.