Crochet Hook Size Chart

BeginnerReference Updated 2026-09-24

Crochet hooks are sized by the diameter of the shaft in millimetres. US hooks add a letter and number: 2.25 mm is B-1, 3.5 mm is E-4, 4 mm is G-6, 5 mm is H-8, 5.5 mm is I-9 and 6 mm is J-10. The millimetre size is the reliable one, so always match the mm number first.

Hook size conversion table

US sizes follow the Craft Yarn Council (CYC) standard. Old UK numbers were used on older hooks and vintage patterns; bigger UK numbers mean smaller hooks. A dash means there is no standard size in that system.

Millimetres	US size	Old UK size
2.25 mm	B-1	—
2.75 mm	C-2	—
3 mm	—	11
3.25 mm	D-3	10
3.5 mm	E-4	—
3.75 mm	F-5	—
4 mm	G-6	8
4.5 mm	7	7
5 mm	H-8	6
5.5 mm	I-9	5
6 mm	J-10	4
6.5 mm	K-10½	3
7 mm	—	2
8 mm	L-11	0
9 mm	M/N-13	00
10 mm	N/P-15	000
11.5 mm	P-16	—
15 mm	P/Q	—
16 mm	Q	—
19 mm	S	—

Brands do not always agree on the letters, especially around 3–3.75 mm. If a pattern gives both mm and a letter, trust the mm size.

Which hook size for amigurumi?

Amigurumi is crocheted tighter than most projects so the stuffing does not show through. The usual rule is to use a hook smaller than the one on the yarn label.

Yarn weight	Label hook (typical)	Common amigurumi hook
Fine / sport (2)	3.5–4.5 mm	2–2.5 mm
Light / DK (3)	4.5–5.5 mm	2.5–3.5 mm
Medium / worsted (4)	5.5–6.5 mm	3.5–4 mm

These are starting points, not rules. If you can see gaps between your stitches, go down another 0.25–0.5 mm. See why amigurumi has holes.

Small hooks and other labels

Hooks under 2.25 mm. Small hooks such as 2 mm are common for amigurumi. They are usually labeled only in mm, or as steel hooks, which use a separate numbering system where a bigger number means a smaller hook.
Japanese-style labels. Some hooks sold in China and Japan are marked like 5/0 or 7/0. 5/0 is 3.0 mm and 7/0 is 4.0 mm. Look for the mm size printed on the hook or packet.
Chinese patterns. Chinese patterns give the hook in mm, for example 钩针 2.5mm or 2.0号钩针 (钩针号数 = hook size).
Check with a gauge. If the size has worn off, push the shaft through the holes of a needle and hook gauge. The smallest hole it fits is its size.

Frequently asked questions

What size is an H crochet hook in mm?

An H-8 hook is 5 mm.

What is the most common crochet hook size?

For worsted-weight yarn, the label usually suggests about 5–5.5 mm (H-8 to I-9). For amigurumi, 2–4 mm hooks are much more common because the stitches need to be tight.

Is a 4 mm hook the same as a G hook?

Yes. In the Craft Yarn Council standard, 4 mm is G-6. Some older US hooks labeled G are 4.25 mm, so check the mm marking if it matters.

Why do UK hook numbers go backwards?

Old UK sizes came from a wire gauge system where a higher number meant thinner wire, so a bigger number means a smaller hook. Modern UK hooks are labeled in mm.

What does 钩针号数 mean?

It means “crochet hook size”. Chinese patterns almost always give it in millimetres, so a 2.5 mm hook is the same size everywhere.