yarn weight conversion guide
Yarn Weight Conversion Guide Chart of Comparisons*:

Yarn Weight Standard
USA
UK
AU
WPI
 0 : LaceLace1 ply2 ply20-40
 1 : Super FineFingering2 ply3 ply14-22
 2 : FineSport4 ply5 ply12-18
 3 : LightLight WorstedDK8 ply11-14
 4 : MediumWorstedAran10 ply9-11
 5 : BulkyBulkyChunky12 ply6-8
 6 : Super BulkySuper BulkySuper Chunky14 ply5-6
 7 : JumboJumbo16 ply0-4

*Reference only based on an aggregate of yarn weight conversion sources comparing yarn weights used in the United States versus yarn weights used in the UK and Australia.

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 mm14
2.25 mmB-113
2.5 mm12
2.75 mmC-2
3.0 mm11
3.25 mmD-310
3.5 mmE-49
3.75 mmF-5
4.0 mmG-68
4.5 mm77
5.0 mmH-86
5.5 mmI-95
6.0 mmJ-104
6.5 mmK-10.53
7.0 mm2
7.5 mm1
8.0 mmL-110
9.0 mmM-1300
10.0 mmN-15000
12 mmO-16
15.0 mmP/Q-19
15.75 / 16.0 mmQ
17.5 mmR
19.0 mmS-35
25.0 mmU

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