Crochet Hook Sizes Chart: mm, US Letters and UK Sizes

Choosing a crochet hook should be easy, but the labels make it confusing: the same hook can be sold as 5 mm, H-8 or UK 6. On top of that, letter sizes are not perfectly standard between brands.

This page puts everything in one place: a full crochet hook size chart in millimeters, US letters and old UK numbers, then the hook that suits each yarn weight. Save it to Pinterest and you will never have to guess again.

Looking for something to make with your new hook? You'll find ad-free, printable PDF patterns in my Etsy shop.

Always Trust the Millimeters

The millimeter size measures the diameter of the hook's shaft, and it is the only number that means exactly the same thing everywhere. US letters and UK numbers are labels attached to those millimeter sizes, and some brands label slightly differently: you will see a G hook sold as 4 mm by one brand and 4.25 mm by another.

So the rule is simple: when a pattern gives a millimeter size, use that. Use the letter only as a quick shortcut.

Crochet Hook Sizes Chart

Standard aluminum and wooden hooks, from small to large. UK numbers come from the old imperial system and are approximate.

Millimeters	US size	Old UK size
2.25 mm	B-1	13
2.75 mm	C-2	12
3.25 mm	D-3	10
3.5 mm	E-4	9
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
8 mm	L-11	0
9 mm	M/N-13	00
10 mm	N/P-15	000
15 mm	P/Q	—
16 mm	Q	—
19 mm	S	—

Notice that old UK numbers go down as the hook gets bigger, the opposite of US sizes. A UK 6 is a 5 mm hook, the size most of my beginner patterns use.

Tip: Hooks smaller than 2 mm are steel hooks for crochet thread, and they use their own numbering where a bigger number means a smaller hook. If a pattern calls for a steel hook, go by the millimeters.

Which Hook for Which Yarn Weight

The yarn label usually suggests a hook range. Here are the standard recommendations from the Craft Yarn Council, which is what most US labels follow:

Yarn weight	Common names	Recommended hook
0 Lace	lace, crochet thread	steel hooks, or 1.6–2.25 mm
1 Super fine	fingering, sock	2.25–3.5 mm (B-1 to E-4)
2 Fine	sport, baby	3.5–4.5 mm (E-4 to 7)
3 Light	DK, light worsted	4.5–5.5 mm (7 to I-9)
4 Medium	worsted, aran	5.5–6.5 mm (I-9 to K-10½)
5 Bulky	chunky	6.5–9 mm (K-10½ to M/N-13)
6 Super bulky	super chunky	9–15 mm (M/N-13 to P/Q)
7 Jumbo	jumbo, roving	15 mm and larger

These are starting points, not rules. Many designers go one or two sizes smaller than the label on purpose:

• Amigurumi and coasters need tight, firm stitches with no holes, so worsted cotton is often worked with a 4–5 mm hook.
• Garments and blankets need drape, so a larger hook gives a softer, more flexible fabric.

How to Choose the Right Hook for a Pattern

1. Start with the hook the pattern gives. It was chosen to make the gauge and the finished size work.
2. Crochet a gauge swatch — a small square of about 4 × 4 inches.
3. Count your stitches. Too many stitches? Your swatch is tight, so go up a hook size. Too few? Go down a size.
4. Adjust before you start, not halfway through. Changing hooks in the middle of a project changes the size of everything after it.

If gauge feels confusing, my guide on how to read a crochet pattern explains what the gauge line means and why it matters.

Hook Materials: Does It Matter?

The size matters most, but the material changes how the yarn glides:

• Aluminum is smooth and fast. A good everyday choice, especially for cotton.
• Ergonomic hooks with a soft handle are kinder to your hands during long sessions.
• Wood and bamboo grip the yarn a little, which helps with slippery yarns.
• Steel is used for very fine hooks and thread crochet.

If your hand gets tired, try an ergonomic handle before you change anything else — it is the single biggest comfort upgrade.

Find Your Next Pattern

With the right hook in hand, you are ready to start. Browse the free patterns here, or pick up an ad-free, printable PDF in my Etsy shop — like the Sunflower Granny Square Cardigan.

Working from a British pattern? Keep my US vs UK crochet terms chart open next to it.