Crochet hooks

Crochet Hook Sizes: US Letters, Millimeters and UK Numbers for Every Hook

Quick answer

Crochet hooks are sized by shank diameter in millimeters, with US letters from B-1 (2.25 mm) to Q (16 mm) and larger jumbo sizes. H-8 is 5 mm and I-9 is 5.5 mm. Steel hooks for thread run in reverse, from size 00 (3.5 mm) to 14 (0.75 mm).

Crochet hook size conversions
Metric	US	Old UK	Yarn weights (CYC)	Size guide
2.25 mm	B-1	13	super fine (fingering)	B-1 guide
2.5 mm	None	12	super fine (fingering)	2.5 mm guide
2.75 mm	C-2	None	super fine (fingering)	C-2 guide
3.125 mm	D	None	super fine (fingering)	See nearest size
3.25 mm	D-3	10	super fine (fingering)	D-3 guide
3.5 mm	E-4	9	super fine (fingering), fine (sport)	E-4 guide
3.75 mm	F-5	None	fine (sport)	F-5 guide
4 mm	G-6	8	fine (sport)	G-6 guide
4.25 mm	G	None	fine (sport)	See nearest size
4.5 mm	7	7	fine (sport), light (DK)	7 guide
5 mm	H-8	6	light (DK)	H-8 guide
5.25 mm	I	None	light (DK)	See nearest size
5.5 mm	I-9	5	light (DK), medium (worsted)	I-9 guide
5.75 mm	J	None	medium (worsted)	See nearest size
6 mm	J-10	4	medium (worsted)	J-10 guide
6.5 mm	K-10.5	3	medium (worsted), bulky (chunky)	K-10.5 guide
7 mm	None	2	bulky (chunky)	7 mm guide
8 mm	L-11	0	bulky (chunky)	L-11 guide
9 mm	M/N-13	00	bulky (chunky), super bulky	M/N-13 guide
10 mm	N/P-15	000	super bulky	N/P-15 guide
11.5 mm	P-16	None	super bulky	P-16 guide
12 mm	None	None	super bulky	See nearest size
15 mm	P/Q	None	super bulky, jumbo	P/Q guide
15.75 mm	Q	None	jumbo	See nearest size
16 mm	Q	None	jumbo	Q guide
19 mm	S	None	jumbo	See nearest size
25 mm	T/U/X	None	jumbo	See nearest size
30 mm	T/X	None	jumbo	See nearest size

Hooks finer than 2.25 mm are steel hooks, numbered in reverse; see the steel crochet hook size chart. Less common in-between sizes such as 4.25 mm G and 5.25 mm I share a page with their nearest standard size, and jumbo hooks from 15.75 to 30 mm are covered on the 16 mm Q page. Work out a blanket foundation with the crochet chain calculator, or compare with the knitting needle size guide.

Researched from manufacturer specifications, owner manuals and verified owner reviews, not hands-on testing, and not professional advice. As an Amazon Associate, Cozy Stitchery earns from qualifying purchases.