Hook & yarn cheat sheet

Yarn weight symbols (0–7), suggested hook sizes in mm and US letters, and typical uses.

CYC	Weight name	Also called	Hook (mm)	Hook (US)	Notes
0	Lace	Thread, cobweb	1.5–2.25 mm	Steel 6–8 / B–1	Very fine thread work, doilies.
1	Super fine	Sock, fingering, baby	2.25–3.5 mm	B–1 to E–4	Amigurumi detail, socks, lightweight garments.
2	Fine	Sport, baby	3.5–4.5 mm	E–4 to 7	Light scarves, baby items.
3	Light	DK, light worsted	4.5–5.5 mm	7 to I–9	Garments, blankets, bags.
4	Medium	Worsted, aran	5.5–6.5 mm	I–9 to K–10½	Most “all-purpose” patterns; check yarn label.
5	Bulky	Chunky, craft	6.5–9 mm	K–10½ to M–13	Quick blankets, hats, thick accessories.
6	Super bulky	Roving	9–15 mm	M–13 to Q	Very fast projects; loose drape unless hook is smaller.
7	Jumbo	Roving, arm crochet	15 mm+	Q and larger	Arm knitting/crochet; specialty hooks.

Stitch choice and tension change drape—your pattern schematic and yarn band override any generic chart.

US crochet hook ↔ mm

Nominal sizes; hooks can differ slightly by brand.