Reference · Updated April 2026

Crochet Hook Size Chart: The Ultimate Metric, US & UK Conversion Reference

Crochet hook sizing is genuinely confusing — three different systems describe the same hooks, and one of them (the UK system) numbers in the opposite direction from the others. This chart resolves every conversion across all three systems, plus the steel hook sizes used for thread crochet, with notes on which hook to pair with each yarn weight.

By Kelley Delano, Editor & Lead Author · Published 25 Jan 2026 · Updated 17 Apr 2026 · 9 min read

🎯 Key takeaway

Crochet hooks are sized in three systems: metric (mm, universal), US (letters and numbers, larger means larger), and UK/Canadian (numbers, smaller means larger — opposite of US). The metric measurement is the diameter of the hook shaft. A US H/8 hook = UK 6 = 5.0 mm — all the same hook. Modern hooks worldwide show the mm size on the handle; trust the mm.

Why crochet hook sizes are so confusing

Three independent systems developed in different countries before any standardisation existed. The metric system is the modern universal — it just measures hook diameter in millimetres (2.0, 2.25, 2.5, etc). The US system uses letters that increase with hook size (B, C, D, ..., S) plus redundant numbers (B/1, H/8, M/13). The UK/Canadian system uses numbers derived from the old Steel Wire Gauge, where smaller numbers mean larger hooks — the reverse of US logic. This UK reversal is the single biggest source of beginner confusion.

Modern hooks (post-1990s) are standardised on metric. Every hook sold today has its mm size stamped on the shaft or handle. If a pattern uses a letter or US number you don't recognise, find the mm equivalent — the mm number is the authoritative measurement.

Complete crochet hook size conversion chart

Every standard size across all three systems. Sizes marked "—" don't have a direct equivalent in that system. The most commonly used sizes (H/8 to K/10.5) are highlighted in your printed pattern context as the workhorse sizes.

Metric (mm)	US	UK / Canadian	Typical yarn weight	Sc gauge (per 4 in)
2.0	—	14	Lace (#0)	24–32
2.25	B/1	13	Lace / Fingering	22–28
2.5	—	12	Fingering	22–26
2.75	C/2	—	Fingering (#1)	21–26
3.0	—	11	Fingering / Sport	20–24
3.25	D/3	10	Sport (#2)	18–22
3.5	E/4	9	Sport / DK	17–20
3.75	F/5	—	DK (#3)	16–18
4.0	G/6	8	DK / Worsted	14–17
4.5	7	7	Worsted (#4)	12–15
5.0	H/8	6	Worsted (#4)	11–14
5.5	I/9	5	Worsted / Bulky	10–13
6.0	J/10	4	Bulky (#5)	9–12
6.5	K/10.5	3	Bulky (#5)	8–11
7.0	—	2	Bulky / Super bulky	8–10
8.0	L/11	0	Super Bulky (#6)	7–9
9.0	M/13	00	Super Bulky (#6)	6–8
10.0	N/15	000	Super Bulky / Jumbo	5–7
12.0	O/16	—	Jumbo (#7)	4–6
15.0	P/Q	—	Jumbo (#7)	4–6
19.0	S	—	Jumbo (#7)	3–5

Steel crochet hooks for thread crochet

Steel hooks are a separate category used for thread crochet — doilies, fine lace, edgings on linens. They're much smaller than yarn hooks, ranging from 0.6 mm to about 2.5 mm. The US numbering for steel hooks is reversed: larger numbers mean smaller hooks. A #14 steel hook is smaller than a #8.

Metric (mm)	US Steel	UK Steel	Use
1.65	4	3	Crochet thread size 5
1.40	5	4	Crochet thread size 5-10
1.30	6	4½	Thread size 10
1.10	7	5	Thread size 10-20
1.00	8	5½	Thread size 20
0.85	10	6	Thread size 30
0.75	12	6½	Thread size 40
0.60	14	7	Thread size 50-70

Which hook for which yarn weight

Yarn labels print a recommended hook range — use that as your starting point. The range exists because individual tension varies. Within the range:

Use the smaller end for: amigurumi (dense fabric, hides stuffing), structural items (baskets, bags that hold shape), firm dishcloths.
Use the middle for: most projects — blankets, scarves, sweaters, the default starting point.
Use the larger end for: drapey fabric (shawls, summer tops), lace patterns, anything you want to feel soft and flowing.

Hook materials and their effect on stitches

The same mm size in different materials produces subtly different stitches:

Aluminium: slick, fast. Yarn glides easily. Slightly tighter stitches because yarn moves freely between loops.
Wood / bamboo: slight friction with yarn. Slightly looser stitches because yarn drags. Quieter; warmer in hand.
Plastic: moderate friction. Lightweight (preferred for jumbo sizes where aluminium would be heavy).
Steel: precise, durable at fine sizes. Used only for thread crochet.

Ergonomic hooks — sizing is the same

Ergonomic hooks (Clover Amour, Tulip Etimo, Furls) use the same standard mm sizing. The handle is the only difference — designed to reduce hand fatigue over long sessions. A 5.0 mm Clover Amour produces the same gauge as a 5.0 mm plain aluminium hook. Choose ergonomic based on hand comfort, not because they produce different fabric.

Buying hooks internationally and online

If you're buying hooks online or from international sources, three rules avoid sizing confusion:

Always confirm the mm size, not just the letter or number. International sellers may list only their own country's notation — but the mm is universal.
Beware of "size kit" listings without specifications. Some budget kits use non-standard sizing (e.g., a 5.2 mm hook labeled as "size H"). Read product details carefully; if the mm sizes aren't listed, the kit may not match standard hook sets.
Watch for steel vs yarn hook confusion. A "Size 8" steel hook is 1.0 mm; a "Size 8" yarn hook is 5.0 mm. These are completely different tools. Always check the mm dimension.

The most reliable international hook brands available worldwide are Clover (Japan), Susan Bates and Boye (US), Pony and Addi (Germany), Tulip (Japan), and Knit Pro / Knitter's Pride (India). All ship globally and use standardised mm sizing.

Frequently asked

Direct answers.

Is a US H/8 hook the same as a UK 6?

Yes. US H/8, UK 6, and metric 5.0 mm describe the same hook diameter. The UK system uses smaller numbers for larger hooks (the reverse of US lettering), which causes most beginner confusion. Modern hooks worldwide are standardised on millimetres.

Why does my UK pattern's hook seem too large?

Because UK numbers go the opposite direction from US. A UK 6 hook is larger than a UK 8 — confusing if you assume the opposite. Always confirm with the mm size, which is universal.

What hook size for worsted weight yarn?

The standard range for worsted (CYC #4) is 5.0 mm (US H/8) to 5.5 mm (US I/9), sometimes up to 6.0 mm (J/10) for drapier fabric. Check your specific yarn's label — it prints a recommended range. Amigurumi in worsted uses 3.5-4.0 mm (smaller than the label suggests) for dense fabric.

Are ergonomic hooks the same sizes as regular hooks?

Yes. Ergonomic hooks (Clover Amour, Tulip Etimo, Furls) use the same standard mm sizing as regular aluminium hooks. The handle shape differs to reduce hand fatigue; the working end (head and shaft) is the same dimension.

What are steel crochet hooks for?

Steel hooks are used for thread crochet — fine doilies, lace edgings, and similar delicate work. They range from 0.6 mm to about 2.5 mm — much smaller than yarn hooks. Note that US steel hook numbering is reversed from yarn hook numbering: larger numbers mean smaller hooks.

How do I know which hook size to start with?

Use the size printed on your yarn label as the starting point — it's the manufacturer's recommendation based on the yarn weight. Make a small swatch with that size, measure your gauge, and adjust up or down by one size if the gauge doesn't match the pattern's target. For non-pattern projects (your own design), the label's recommended size is usually correct.

Sources & further reading

Craft Yarn Council — Standard Yarn Weight System
Crochet Guild of America (CGOA) — professional standards
Edie Eckman, The Crochet Answer Book (Storey Publishing) — technique reference
Clara Parkes, The Knitter's Book of Yarn (Potter Craft) — fibre properties

Kelley Delano

Editor & Lead Author

Kelley is the editor and lead author at Crochet Calc. She works across the site's calculator math, reference articles, and editorial standards, focused on making professional-grade project planning accessible to crocheters at every skill level.

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