Crochet hooks
Crochet Hook Sizes: US Letters, Millimeters and UK Numbers for Every Hook
Crochet hooks are sized by shank diameter in millimeters, with US letters from B-1 (2.25 mm) to Q (16 mm) and larger jumbo sizes. H-8 is 5 mm and I-9 is 5.5 mm. Steel hooks for thread run in reverse, from size 00 (3.5 mm) to 14 (0.75 mm).
The table below converts every crochet hook size between metric, US letters and old UK numbers and shows the yarn weights each one suits: the H-8, the size most beginner patterns name, is 5 mm, and the I-9 at 5.5 mm is the finest hook CYC lists for worsted weight yarn.
| Metric | US | Old UK | Yarn weights (CYC) | Size guide |
|---|---|---|---|---|
| 2.25 mm | B-1 | 13 | super fine (fingering) | B-1 guide |
| 2.5 mm | None | 12 | super fine (fingering) | 2.5 mm guide |
| 2.75 mm | C-2 | None | super fine (fingering) | C-2 guide |
| 3.125 mm | D | None | super fine (fingering) | See nearest size |
| 3.25 mm | D-3 | 10 | super fine (fingering) | D-3 guide |
| 3.5 mm | E-4 | 9 | super fine (fingering), fine (sport) | E-4 guide |
| 3.75 mm | F-5 | None | fine (sport) | F-5 guide |
| 4 mm | G-6 | 8 | fine (sport) | G-6 guide |
| 4.25 mm | G | None | fine (sport) | See nearest size |
| 4.5 mm | 7 | 7 | fine (sport), light (DK) | 7 guide |
| 5 mm | H-8 | 6 | light (DK) | H-8 guide |
| 5.25 mm | I | None | light (DK) | See nearest size |
| 5.5 mm | I-9 | 5 | light (DK), medium (worsted) | I-9 guide |
| 5.75 mm | J | None | medium (worsted) | See nearest size |
| 6 mm | J-10 | 4 | medium (worsted) | J-10 guide |
| 6.5 mm | K-10.5 | 3 | medium (worsted), bulky (chunky) | K-10.5 guide |
| 7 mm | None | 2 | bulky (chunky) | 7 mm guide |
| 8 mm | L-11 | 0 | bulky (chunky) | L-11 guide |
| 9 mm | M/N-13 | 00 | bulky (chunky), super bulky | M/N-13 guide |
| 10 mm | N/P-15 | 000 | super bulky | N/P-15 guide |
| 11.5 mm | P-16 | None | super bulky | P-16 guide |
| 12 mm | None | None | super bulky | See nearest size |
| 15 mm | P/Q | None | super bulky, jumbo | P/Q guide |
| 15.75 mm | Q | None | jumbo | See nearest size |
| 16 mm | Q | None | jumbo | Q guide |
| 19 mm | S | None | jumbo | See nearest size |
| 25 mm | T/U/X | None | jumbo | See nearest size |
| 30 mm | T/X | None | jumbo | See nearest size |
Hooks finer than 2.25 mm are steel hooks, numbered in reverse; see the steel crochet hook size chart. Less common in-between sizes share a page with their nearest standard size, so the 4.25 mm G is covered on G-6 (4 mm) and the 5.25 mm I on I-9 (5.5 mm), and jumbo hooks from 15.75 to 30 mm are covered on the 16 mm Q page. Work out a blanket foundation with the crochet chain calculator, or compare with the knitting needle size guide.
Frequently asked questions
What size crochet hook should I use?
Start with the hook printed on the yarn band. For worsted weight CYC lists 5.5 to 6.5 mm (I-9 to K-10.5), though plenty of beginner patterns name the H-8, a 5 mm hook, one step finer. Then swatch: if your stitches are smaller than the pattern gauge go up a size, and if they are larger go down. Hook size sets fabric density as much as it sets size.
What is the best crochet hook size for a blanket?
For a worsted weight blanket, 5.5 to 6.5 mm (I-9 to K-10.5): a 50 inch wide throw starts with about 157 chains at 11 to 14 single crochet per 4 inches. For a fast chunky blanket, a Q hook at 16 mm with jumbo yarn drops the same 50 inches to roughly 76 chains. Bigger hooks finish sooner and drape softer, smaller hooks give a denser and warmer fabric.
What size crochet hook do you use for amigurumi?
Amigurumi is worked a size or two smaller than the ball band suggests, so the stuffing cannot show through the stitches. With worsted weight yarn that usually means something closer to 3.5 to 4.5 mm rather than the 5.5 to 6.5 mm (I-9 to K-10.5) CYC lists, and with DK a 3.5 mm E-4 hook is common. Work a small swatch first: if you can see daylight between the stitches, go down again. The amigurumi size calculator scales a pattern to a finished height.
Are crochet hook letters the same in every brand?
No. Letters and numbers drift between brands and countries, especially at the large end, where one letter can cover two diameters, so the millimeter size stamped on the shank is the one to trust, and the crochet hook size chart lists every one of them. Some sizes carry no US letter at all, such as the 2.5 mm hook. Thread hooks use a separate scale that runs backwards, with higher numbers finer.
Researched from manufacturer specifications, owner manuals and verified owner reviews, not hands-on testing, and not professional advice. As an Amazon Associate, Cozy Stitchery earns from qualifying purchases.
