Yarn Weights & Categories:
0 = Lace [fingering 10 count crochet thread or light fingering yarn or cobweb weight] — Steel hook 6, 7, 8 or B-1 hook
1 = Super Fine [sock, fingering baby yarn] — B-1 to E-4 hook
2 = Fine [sport, baby yarn] — E-4 to 7hook
3 = Light [DK {double knit}, light worsted yarn] — 7 to I-9 hook
4 = Medium [worsted, afghan, aran yarn] — I-9 to K-10 1/2 hook
5 = Bulk [chunky, craft, rug yarn] — K-10 1/2 to M-13 hook
6 = Super Bulky [super bulky, roving yarn] — M-13 to Q hook
7 = Jumbo [jumbo, roving yarn] — Q and larger
Speciality Yarns and Fabrics {stripped for crochet}