Japanese Crochet Hook Sizes: A Straightforward Conversion Table
Japanese hook sizes (2/0, 5/0, 7.5/0) in mm and US letters, plus lace hooks 0 to 14 and jumbo hooks, with a note on which sizes have no US match.
On this page
Japanese crochet hooks are labeled 2/0, 3/0, 4/0 … 10/0 (plus 7.5/0), and the number is just a code for a millimeter size. 5/0 is 3.0 mm, 6/0 is 3.5 mm, 7/0 is 4.0 mm, 7.5/0 is 4.5 mm, and 8/0 is 5.0 mm. Lace hooks work in reverse: a bigger number is a thinner hook. Below you will find every size in millimeters with the nearest US size, and an honest note wherever the US system has nothing that fits.
Checked against the makers’ own pages on 2026-10-17.
Three scales, three kinds of hook
Japanese hooks come in three families, and each has its own numbering. Mixing them up is the most common mistake.
- かぎ針 (kagi-bari, “crochet hook”): the /0 sizes (2/0 to 10/0). Bigger number = thicker hook.
- レース針 (rēsu-bari, “lace hook”): plain numbers (No.0, 2, 4 … 14). Bigger number = thinner hook.
- Jumbo hooks: thicker than 10/0, labeled in plain millimeters (7 mm, 8 mm, 10 mm and so on).
Clover’s explainer for crochet tools puts the first two together: lace hook 0号 is the thickest lace hook, and the hooks get thinner as the numbers go up. Hooks thicker than lace 0 are called かぎ針. That is where the slash numbers come from: in Clover’s explanation, these hooks were counted as 00 (ニイレー, nii-rē) and 000 (サンレー, san-rē), which are written 2/0 and 3/0. Clover prints the millimeter size next to the number on its tools.
Quick chart: かぎ針 (/0 sizes) to mm and US
| Japanese size | mm (Clover; Hamanaka for all but 9/0) | Nearest US (CYC) | Notes |
|---|---|---|---|
| 2/0 | 2.0 | no US match | CYC’s crochet table starts at 2.25 mm (B-1) |
| 3/0 | 2.3 | ≈ B-1 (2.25 mm) | Tulip lists 3/0 as 2.2 mm |
| 4/0 | 2.5 | no US match | CYC shows 2.5 mm with no US size |
| 5/0 | 3.0 | no US match | between C-2 (2.75 mm) and D (3.125 mm) |
| 6/0 | 3.5 | E-4 (exact) | |
| 7/0 | 4.0 | G-6 (exact) | |
| 7.5/0 | 4.5 | 7 (exact) | CYC labels it plain “7” |
| 8/0 | 5.0 | H-8 (exact) | |
| 9/0 | 5.5 | I-9 (exact) | Clover’s sheet lists 9/0 = 5.5 mm. Hamanaka’s single-ended hook list skips from 8/0 to 10/0; 9/0 appears there only as the end of its double-ended 7.5/0-9/0 hook (4.5 to 5.5 mm) |
| 10/0 | 6.0 | J-10 (exact) |
Two things to notice. First, the larger sizes (6/0 and up) line up exactly with US sizes. The small ones (2/0 to 5/0) mostly do not, so for amigurumi and lace-weight work you are really converting by millimeters. Second, ”≈” means within 0.05 mm of the US size, which is a gap most crocheters will never feel.
Tulip, a major hook maker, sells a finer ladder of sizes, which you may run into in Japanese shops:
| Tulip size | mm | Nearest US (CYC) |
|---|---|---|
| 1/0 | 1.80 | no US match |
| 2/0 | 2.00 | no US match |
| 3/0 | 2.20 | ≈ B-1 (2.25 mm) |
| 4/0 | 2.50 | no US match |
| 4.5/0 | 2.75 | C-2 (exact) |
| 5/0 | 3.00 | no US match |
| 5.5/0 | 3.25 | D-3 (exact) |
| 6/0 | 3.50 | E-4 (exact) |
| 6.5/0 | 3.75 | F-5 (exact) |
| 7/0 | 4.00 | G-6 (exact) |
| 7.5/0 | 4.50 | 7 (exact) |
| 8/0 | 5.00 | H-8 (exact) |
| 9/0 | 5.50 | I-9 (exact) |
| 10/0 | 6.00 | J-10 (exact) |
| 10.5/0 | 6.50 | K-10½ (exact) |
The one disagreement between makers is 3/0: Clover and Hamanaka say 2.3 mm; Tulip says 2.20 mm. If your pattern needs 3/0, check which brand you are buying.
Lace hooks (レース針): bigger number, thinner hook
Lace hooks are numbered in the opposite direction from everything else in this article. Clover and Tulip print the same millimeters for the standard set:
| Lace hook number | mm |
|---|---|
| No.0 | 1.75 |
| No.2 | 1.50 |
| No.4 | 1.25 |
| No.6 | 1.00 |
| No.8 | 0.90 |
| No.10 | 0.75 |
| No.12 | 0.60 |
| No.14 | 0.50 |
Tulip also makes thinner hooks. Its Etimo Rose lace hooks add No.15 (0.45 mm) and No.16 (0.40 mm). Its separate grip extra-fine hooks are No.23 (0.45 mm), No.24 (0.40 mm), and No.25 (0.35 mm), and Tulip states that No.23, 24, and 25 are its own numbering, not an industry scale. So a No.23 and a No.15 are both 0.45 mm, and if a pattern asks for one of those you should go by the millimeters.
US steel hooks are also numbered backwards (higher number, smaller hook). The Craft Yarn Council says the smallest steel hook is a #14 (0.9 mm) and the largest is a 00 (2.7 mm), which is not the same ladder as Japan’s lace numbers. Its steel-hook page also notes that steel hook numbering varies, so for lace or thread work, compare hooks by millimeters.
Jumbo hooks (mm only)
Past 10/0 there are no /0 numbers. Hooks are labeled in millimeters.
| Jumbo hook (mm) | US (CYC) | Examples seen on maker pages |
|---|---|---|
| 7 | no US match | Clover, Tulip (ジャイアントかぎ針) |
| 8 | L-11 | Clover, Tulip, Hamanaka (竹製かぎ針) |
| 10 | N/P-15 | Clover, Tulip, Hamanaka |
| 12 | no US match | Clover, Tulip, Hamanaka |
| 15 | P/Q | Clover, Hamanaka (ビッグ針) |
| 20 | CYC lists 19 mm (S) and 25 mm (T/U/X) | Hamanaka (ビッグ針) |
A note on names: ジャンボ (janbo, “jumbo”) is a registered trademark of Clover, so other brands use other words. Tulip says ジャイアント (jaianto, “giant”), and Hamanaka says ビッグ針 (biggu-bari, “big hook”) for the biggest sizes.
How to use a hook size from a Japanese pattern
A Japanese pattern or yarn label might say 「かぎ針 7/0号」. Here is the sequence:
- Read the /0 number, or the lace number if it says レース針.
- Convert to millimeters with the chart above (7/0 = 4.0 mm).
- If you only have US hooks, take the nearest US size, or go by mm if your hook shows it.
- Swatch. Hamanaka’s guidance is that “standard gauge” is only the typical result with the stated hook, that gauge varies a lot from person to person, and that you should check it on a larger test piece and change the hook size if needed.
Two examples from real yarn pages: Hamanaka’s Bonny acrylic lists its recommended crochet hook as 7.5/0, and Daruma’s Merino Wool DK lists 6/0 to 7/0. Converting those gives 4.5 mm and 3.5 to 4.0 mm. For more on reading those yarn pages, see the yarn label guide.
If you are starting amigurumi, the symbols and terms are covered in the Japanese crochet symbols guide and わ・目・段.
FAQ
What size is a 5/0 crochet hook? 3.0 mm. There is no exact US match: C-2 is 2.75 mm and D is 3.125 mm. Use millimeters or swatch.
Is 7.5/0 the same as US 7? Yes. 7.5/0 is 4.5 mm, which CYC labels as US 7. It is one of the sizes that line up exactly.
Is a higher lace hook number thicker or thinner? Thinner. No.0 is 1.75 mm and No.14 is 0.5 mm. The /0 hooks go the other way: 10/0 is thicker than 2/0.
Do I need a Japanese hook for a Japanese pattern? No. Convert the size to millimeters and use any hook of that size.
Do the numbers match the knitting needle numbers? No. Needles use plain numbers (0号 to 15号) on a different scale. See the needle size chart.
Sources
All pages below were opened on 2026-10-17.
- Clover, crochet tool basics (lace and hook numbering, ニイレー/サンレー): https://clover.co.jp/knitting/crochet_tool
- Clover, 2026年度 needle and hook spec sheet (PDF): http://www.clover.co.jp/recipe/takumikikakus.pdf
- Clover, 「ジャンボ」 trademark note: https://clover.co.jp/seihin/jumboamure.html
- Tulip, Etimo Red hook sizes (mm per size): https://www.tulip-japan.com/?pid=148686509
- Tulip, Etimo lace hooks: https://www.tulip-japan.com/?pid=148692845
- Tulip, Etimo Rose lace hooks (to No.16): https://www.tulip-japan.com/?pid=148689984
- Tulip, grip extra-fine lace hooks No.23-25: https://www.tulip-japan.com/?pid=148696236
- Tulip, giant crochet hooks 7 to 12 mm: https://www.tulip-japan.com/?pid=148689383
- Hamanaka, tool list (single-ended hooks, bamboo hook, ビッグ針): https://hamanaka.jp/goods/tool_teami
- Hamanaka, double-ended hook 7.5/0-9/0 (4.5 to 5.5 mm): https://hamanaka.jp/items/h250-500-7
- Hamanaka, Bonny yarn page (recommended hook 7.5/0): https://hamanaka.jp/hamanaka/4057
- Hamanaka Q&A, standard gauge and swatching: http://www.hamanaka.co.jp/qa/teami_q11.html
- Daruma (Yokota), Merino Wool DK product page (recommended hook 6/0 to 7/0): https://www.daruma-ito.co.jp/products/01-6700.php
- Craft Yarn Council, Hooks & Needles standards (US sizes, steel hook note): https://craftyarncouncil.com/standards/hooks-and-needles
- Craft Yarn Council, steel crochet hook and thread sizes (numbering varies): https://craftyarncouncil.com/standards/steel-crochet-hook-crochet-thread-sizes