Crochet hook sizes explained: the complete US guide for amigurumi & beyond

You bought the yarn. You picked the pattern. And then the hook recommendation stopped you cold: B/1? H/8? 3.5 mm? UK size 9? Crochet hook sizing looks like a secret code the first time you meet it — and even experienced crocheters mix up the systems when a pattern hops between US letters, UK numbers, and metric millimeters without warning.

Why hook size matters more than you think

Your hook is not just a tool — it is the dial that controls the size, tension, and personality of every stitch you make.

Crochet the same pattern with a 3.0 mm hook and again with a 5.0 mm hook, using identical yarn, and you will get two objects that look and feel completely different. Hook size directly affects:

• Stitch density — how tightly or loosely your stitches sit together
• Finished dimensions — the physical size of the completed piece
• Drape — how the fabric hangs, folds, and moves
• Stuffing visibility — critical for amigurumi, where loose stitches let white stuffing show through
• Durability — tighter fabric means longer-lasting plushies, bags, and coasters

Getting the size right is not about perfection. It is about making sure the thing you create matches the thing the designer intended. If your stitches keep coming out uneven no matter which hook you use, the fix is usually in your hands, not your tools — our guides to holding your crochet hook and getting even tension walk you through it.

The complete US hook size chart, letters to millimeters

US hooks carry a letter-and-number label plus a metric measurement. The millimeter number is the one that never lies.

Here is the full standard US range and what each size is typically used for:

• Steel hooks (0.6–3.5 mm) — thread crochet and lace; their numbering runs backwards, so higher numbers mean smaller hooks
• B/1 — 2.25 mm, C/2 — 2.75 mm — fingering and sport yarn, tiny amigurumi
• D/3 — 3.25 mm, E/4 — 3.5 mm — DK yarn, small plushies and amigurumi animals
• F/5 — 3.75 mm, G/6 — 4.0 mm — light worsted amigurumi, hats, small bags
• H/8 — 5.0 mm — the most popular beginner hook: hats, scarves, dishcloths with worsted yarn
• I/9 — 5.5 mm, J/10 — 6.0 mm — blankets, cardigans, chunky bags
• K/10.5 — 6.5 mm, L/11 — 8.0 mm — bulky projects, fast blankets, rugs
• M/13 — 9.0 mm through S — 19.0 mm — super bulky and jumbo yarn, oversized throws

One important caveat: letter assignments can vary slightly between brands. One manufacturer's G hook may be 4.0 mm while another's measures 4.25 mm. The mm number stamped on the hook is the reliable standard, so always confirm by millimeters when mixing brands. For a printable side-by-side table of every conversion, see our complete mm-to-letters conversion chart.

US vs UK vs metric: three systems, one answer

This is where most of the confusion starts. The US, UK, and metric systems all label the same physical hooks differently — and the UK numbering runs in the opposite direction, so a bigger UK number means a smaller hook.

A few anchor points show how differently the systems behave:

• 2.25 mm = US B/1 = UK 13
• 4.0 mm = US G/6 = UK 8
• 5.0 mm = US H/8 = UK 6
• 6.0 mm = US J/10 = UK 4

See the trap? A UK "size 4" is a 6.0 mm hook, while a US E/4 is only 3.5 mm. The rule that solves everything: whenever a pattern names a hook, translate it to millimeters before you pick anything up. Millimeters are universal in every country and every brand.

The best hook size for amigurumi

Amigurumi plays by its own rules: you almost always go smaller than the yarn label says.

With scarves and blankets, you generally follow the hook size printed on the yarn label. Amigurumi is different because the pieces are stuffed. If your stitches are too open, the stuffing shows through every gap — the number one complaint we hear from new plushie makers, and the exact problem we troubleshoot in why does my amigurumi have holes.

These pairings produce the firm, clean fabric amigurumi needs:

• Fingering (weight 1): 1.5–2.0 mm hook
• Sport (weight 2): 2.5–3.0 mm hook
• DK (weight 3): 2.75–3.5 mm hook
• Worsted (weight 4): 3.5–4.0 mm hook
• Bulky (weight 5): 4.5–5.5 mm hook

The most common starting point is DK yarn with a 3.0 mm or 3.5 mm hook — firm enough to hold its shape, loose enough to be kind to your hands. If a pattern skips the hook size, start 0.5–1.0 mm below the yarn label recommendation and crochet a small test circle: a magic ring with 6 single crochet, increased to 12, then 18. Daylight between stitches means go smaller; cardboard-stiff fabric means go up 0.25 mm. Yarn choice matters just as much — our comparison of cotton vs acrylic for amigurumi covers which fiber behaves best at tight tension.

Matching hook size to yarn weight for everything else

For garments, bags, blankets, and home décor, yarn and hook sizes are designed as partners. The standard pairings:

• Lace / thread (weight 0): 1.5–2.25 mm steel hooks
• Fingering (weight 1): 2.25–3.25 mm
• Sport (weight 2): 3.25–3.75 mm
• DK (weight 3): 3.5–4.5 mm — the most popular amigurumi weight
• Worsted (weight 4): 5.0–5.5 mm — most beginner projects
• Bulky (weight 5): 6.0–8.0 mm
• Super bulky and jumbo (weights 6–7): 9.0 mm and up

US yarn labels print a little hook icon with the recommended size right on the band — use it as your starting point for wearables, and drop down for amigurumi as described above.

Does hook material change anything?

Yes — material affects glide, grip, and the tension your hands naturally create.

Aluminum is the workhorse: affordable, durable, with just enough drag to help you control tension — the most practical choice for amigurumi in the 2.5–4.0 mm range. Plastic hooks are lightweight and add friction that tames slippery yarns; almost all jumbo hooks are plastic. Wood and bamboo feel warm and slightly grippy, lovely for bulky yarn but fragile at small sizes. Ergonomic hooks pair a standard metal head with a cushioned handle — a genuine game-changer for long sessions or anyone with hand pain.

One golden rule regardless of material: never switch hooks mid-project, even to the same labeled size in a different brand or material. Your tension will shift and the change will show. For specific recommendations, see our roundup of the best crochet hooks for beginners.

How to use a gauge swatch to pick your hook

Gauge tells you how many stitches and rows fit into a set measurement, usually 4 inches / 10 cm. For wearables and bags where finished size matters, always swatch first: chain 15–20 with the recommended hook, single crochet 15–20 rows, lay the swatch flat, and count the stitches and rows in a 4-inch square at the center. More stitches than the pattern states means your tension is tight — go up a hook size. Fewer means loose — go down one. A single size up or down usually closes the gap. For amigurumi, exact gauge matters far less than fabric tightness: you are swatching for density, not dimensions.

Five hook-size mistakes to skip

1. Trusting the letter alone. Letters are not standardized across brands — check the mm stamp, and measure with a hook gauge if it has worn off.

2. Using the yarn label size for amigurumi. Worsted yarn says 5.0 mm; use that for a plushie and stuffing shows through every stitch. Drop to 3.5–4.0 mm instead.

3. Confusing US and UK patterns. A UK size 4 is 6.0 mm — nearly double a US E/4 at 3.5 mm. Convert to mm before you start.

4. Switching hooks mid-project. Same labeled size, different brand or material, different tension. Finish with the hook you started with.

5. Trusting cheap sets blindly. Budget sets sometimes mislabel sizes by up to half a millimeter — verify with a hook gauge before an important project.

Frequently asked questions