Crochet Hook Size Chart

Why sizing isn't consistent

US letter sizes and old UK/Canada sizes were standardized decades apart by different organizations, and neither system was built with the other in mind — that's why they don't convert on a clean 1:1 basis. Two hooks with different letters can be the exact same metric size, and a single letter (like G) can map to a different millimeter size depending on which country's chart you're reading. When following a pattern from a different region, match the metric millimeter size if it's given at all, since that's the one measurement that's physically the same regardless of what a manufacturer printed on the handle.

When the size stamped on the hook is worn off

Cheap or older hooks sometimes lose their printed size entirely. Rather than guessing, lay the hook's shaft across a ruler or gauge tool with pre-cut holes sized to standard hook diameters — the size that fits snugly (not loosely, not forced) is the real one. Steel hooks used for thread crochet run on a completely separate numbering scale from the lettered aluminum/plastic hooks used for yarn, and confusingly the numbers run in the opposite direction: a steel size 12 is much finer than a steel size 1, while a lettered B-1 is smaller than a K-10.5. If a thread pattern calls for a steel hook, don't substitute a same-numbered yarn hook — they aren't related sizes at all.

How to Choose a Crochet Hook Size

The chart above converts between US letters and millimeters. Choosing which size to actually pick up is a different question, and the answer isn't simply "whatever the yarn label says" — the label gives you a starting point, and the project decides whether to move up or down from it.

Start from the yarn, not the pattern

Every yarn label carries a recommended hook size, and it's a reasonable default for general-purpose fabric — blankets, scarves, garments. Here's the usual pairing:

Yarn weight	Common name	Typical hook
1 — Super fine	Fingering, sock	2.25–3.5 mm (B-1 to E-4)
2 — Fine	Sport	3.5–4.5 mm (E-4 to 7)
3 — Light	DK	4.5–5.5 mm (7 to I-9)
4 — Medium	Worsted, aran	5.5–6.5 mm (I-9 to K-10.5)
5 — Bulky	Chunky	6.5–9 mm (K-10.5 to M-13)
6 — Super bulky	Super chunky	9–15 mm (M-13 to Q)

The yarn and hook converter handles this pairing directly, including the equivalent needle sizes.

When to go smaller than the label

Amigurumi, always. Stuffed toys need dense fabric that stuffing can't show through, so the standard is a hook one to two sizes smaller than the label recommends — worsted yarn on a 3.5 or 4.0 mm hook rather than 5.5. The fabric feels stiff off the hook, which is correct; it becomes right once stuffed.

Anything that needs structure. Bags, baskets, coasters, and hat brims all benefit from a tighter fabric that holds its shape rather than draping.

When to go larger

Drape. Shawls, wraps, and summer garments want fabric that flows, and a larger hook opens the stitches up. A worsted yarn on an 8 mm hook makes something surprisingly light and fluid.

Tight tension. If your stitches habitually come out small and your fabric feels stiff, going up a size is the fix — and it's a far more reliable fix than trying to consciously crochet looser, which never lasts more than a few rows.

The size that matters is the one that gets gauge

This is the part that overrides everything above. If a pattern specifies a gauge, the hook size printed in that pattern is only the designer's starting point — it was the size they needed to hit that gauge. Your hands are different.

Swatch, measure, and change hook size until you match. Needing to go two sizes up or down from the pattern is completely normal and says nothing about your skill. Following the stated hook size and ignoring the gauge is how garments come out two sizes wrong. See the gauge guide for how to swatch properly.

Hook material changes your gauge

Material	Feel	Effect
Aluminum	Slick, fast	Stitches slide easily — usually slightly looser fabric. The best all-round choice.
Steel	Very fine, rigid	For thread crochet and lace only.
Plastic / acrylic	Light, some drag	Common in large sizes where metal would be heavy.
Bamboo / wood	Warm, grippy	More friction, often slightly tighter fabric. Good for slippery yarns.
Ergonomic handles	Padded grip	Same hook sizes, far less hand strain. Worth it if you crochet for hours.

Switching material mid-project can shift your gauge measurably, so finish a piece with the hook you started it with.

The head shape nobody mentions

Hooks come with two head profiles, and they feel genuinely different. Inline hooks (Susan Bates being the common example) have a head that sits flush with the shaft, giving consistent stitch size and a firm grip on the yarn. Tapered hooks (Boye and most others) have a rounded, gradual head that slides into stitches more easily and snags less.

Neither is better. Most crocheters have a strong preference once they've tried both, and many people struggling with an unexplained tension problem simply have the profile that doesn't suit them.

A note on sizing consistency

Letters are not a reliable standard. One brand's H may be 5.0 mm and another's 5.25 mm, and older or imported hooks vary more. Trust the millimeter marking, not the letter — millimeters are an actual measurement and letters are a convention. When a pattern gives only a letter, convert it with the chart above and use the millimeter size.

Common problems

Problem	Cause and fix
Fabric is stiff and boardy	Hook too small for the yarn. Go up a size or two.
Fabric is loose and holey	Hook too large. Go down, especially for amigurumi.
Stuffing shows through a toy	Hook too big. Amigurumi needs 1–2 sizes below the label.
Can't match the pattern's gauge	Change hook size until you do. The pattern's stated size is a starting point, not a rule.
Size worn off the hook	Measure the shaft with a hook gauge, or against the chart above.
Hands ache after an hour	Try an ergonomic handle and a looser grip. Pain is not part of the craft.

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