Crochet Hook Size Chart: mm, US Letters & UK Sizes

Hook size conversion chart

Metric (mm)	US size	Old UK size
2.0 mm	—	14
2.25 mm	B-1	13
2.5 mm	—	12
2.75 mm	C-2	—
3.0 mm	—	11
3.125 mm	D	—
3.25 mm	D-3	10
3.5 mm	E-4	9
3.75 mm	F-5	—
4.0 mm	G-6	8
4.25 mm	G	—
4.5 mm	7	7
5.0 mm	H-8	6
5.25 mm	I	—
5.5 mm	I-9	5
5.75 mm	J	—
6.0 mm	J-10	4
6.5 mm	K-10½	3
7.0 mm	—	2
8.0 mm	L-11	0
9.0 mm	M/N-13	00
10.0 mm	N/P-15	000
11.5 mm	P-16	—
12 mm	—	—
15 mm	P/Q	—
15.75 mm	Q	—
16 mm	Q	—
19 mm	S	—
25 mm	T/U/X	—
30 mm	T/X	—

US letters and numbers can vary between manufacturers. When a pattern gives both systems, follow the millimeter size. Historical UK numbers are included for older patterns; verify an unusual vintage size against the pattern or hook packaging.

Which hook for which yarn?

The yarn label usually suggests a hook. In the standard ranges, super fine or sock yarn starts at 2.25–3.5 mm, light or DK at 4.5–5.5 mm, medium or worsted at 5.5–6.5 mm, and bulky at 6.5–9 mm. These are guidelines only. Follow the pattern gauge and judge whether the fabric has the required firmness or drape. See the yarn weight guide for the full table.

Matching the pattern’s gauge

Crochet a swatch at least 5 in (13 cm) square in the pattern’s stitch.
Measure the stitches over 4 in (10 cm) in the middle of the swatch.
Too many stitches → your fabric is tight: try a larger hook.
Too few stitches → your fabric is loose: try a smaller hook.

New to crochet? How to crochet explains how to hold the hook, and the gauge swatch guide shows how to choose the size that matches a pattern.

Metric and US sizes: Craft Yarn Council — Hooks & needles. Source: Craft Yarn Council's www.YarnStandards.com.

Questions

What is the most common crochet hook size?

There is no single size for every project. Medium (4) yarn commonly uses a 5.5–6.5 mm hook as a starting range, but the pattern gauge decides the final size.

Is a 5 mm hook the same as an H hook?

The Craft Yarn Council chart pairs 5 mm with US H-8. Check the millimeter marking because letter sizes can vary between manufacturers.

What size hook is best for beginners?

Choose the range on the yarn label or beginner pattern. A smooth medium yarn and a comfortable hook make stitches easier to see, but the gauge still needs to match.

Do UK patterns use different hook sizes?

Current UK patterns generally state metric millimeters. Historical patterns may use old UK numbers, so confirm vintage instructions against a conversion chart.