Crochet hook and knitting needle sizes
An H-8 crochet hook is 5 mm and a US 8 knitting needle is 5 mm too, on the Craft Yarn Council chart. Millimeters are the only size that means the same everywhere.
Crochet hook and knitting needle sizes: the tool
Convert a hook or needle size
Actual thickness
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Crochet hook sizes
| mm | US |
|---|---|
| 2.25 | B-1 |
| 2.5 | n/a |
| 2.75 | C-2 |
| 3.125 | D |
| 3.25 | D-3 |
| 3.5 | E-4 |
| 3.75 | F-5 |
| 4 | G-6 |
| 4.25 | G |
| 4.5 | 7 |
| 5 | H-8 |
| 5.25 | I |
| 5.5 | I-9 |
| 5.75 | J |
| 6 | J-10 |
| 6.5 | K-10 1/2 |
| 7 | n/a |
| 8 | L-11 |
| 9 | M/N-13 |
| 10 | N/P-15 |
| 11.5 | P-16 |
| 12 | n/a |
| 15 | P/Q |
| 15.75 | Q |
| 16 | Q |
| 19 | S |
| 25 | T/U/X |
| 30 | T/X |
Knitting needle sizes
| mm | US |
|---|---|
| 1.5 | 000 |
| 1.75 | 00 |
| 2 | 0 |
| 2.25 | 1 |
| 2.75 | 2 |
| 3 | n/a |
| 3.125 | 3 |
| 3.25 | 3 |
| 3.5 | 4 |
| 3.75 | 5 |
| 4 | 6 |
| 4.25 | 6 |
| 4.5 | 7 |
| 5 | 8 |
| 5.25 | 9 |
| 5.5 | 9 |
| 5.75 | 10 |
| 6 | 10 |
| 6.5 | 10 1/2 |
| 7 | n/a |
| 8 | 11 |
| 9 | 13 |
| 10 | 15 |
| 12.5 | 17 |
| 12.75 | 17 |
| 15 | 19 |
| 19 | 35 |
| 25 | 50 |
| 35 | 70 |
Old UK and Japanese needle sizes
| mm | US | Old UK | Japanese |
|---|---|---|---|
| 0.5 | 8/0 | 24 | n/a |
| 0.7 | 6/0 | 22 | n/a |
| 1 | 5/0 | 19 | n/a |
| 1.25 | 4/0 | 18 | n/a |
| 1.5 | 000 | 17 | n/a |
| 1.75 | 00 | 15 | n/a |
| 2 | 0 | 14 | n/a |
| 2.1 | n/a | n/a | 0 |
| 2.25 | 1 | 13 | n/a |
| 2.4 | n/a | n/a | 1 |
| 2.7 | n/a | n/a | 2 |
| 2.75 | 2 | 12 | n/a |
| 3 | 2 1/2 | 11 | 3 |
| 3.25 | 3 | 10 | n/a |
| 3.3 | n/a | n/a | 4 |
| 3.6 | n/a | n/a | 5 |
| 3.75 | 5 | 9 | n/a |
| 3.9 | n/a | n/a | 6 |
| 4 | 6 | 8 | n/a |
| 4.25 | n/a | n/a | 7 |
| 4.5 | 7 | 7 | 8 |
| 4.75 | n/a | n/a | 9 |
| 5 | 8 | 6 | n/a |
| 5.1 | n/a | n/a | 10 |
| 5.4 | n/a | n/a | 11 |
| 5.5 | 9 | 5 | n/a |
| 5.75 | n/a | n/a | 12 |
| 6 | 10 | 4 | 13 |
| 6.3 | n/a | n/a | 14 |
| 6.5 | 10 1/2 | 3 | n/a |
| 6.6 | n/a | n/a | 15 |
| 7 | n/a | 2 | 7 mm |
| 7.5 | n/a | 1 | n/a |
| 8 | 11 | 0 | 8 mm |
| 9 | 13 | 00 | 9 mm |
| 10 | 15 | 000 | 10 mm |
| 16 | 19 | n/a | 16 mm |
| 25 | 50 | n/a | 25 mm |
Steel crochet hooks
CYC's steel hook table lists several numbering schemes side by side; the same US number appears at different mm sizes (for example 00 at 3.50 mm and 2.70 mm). CYC says steel hook numbering varies by maker and the higher the number, the smaller the hook.
Related tools
Related: Row counter, Knitting gauge calculator.
Questions
What size is an H crochet hook?
H-8 is 5 mm on the Craft Yarn Council chart.
What is a size 8 knitting needle in mm?
US 8 is 5 mm.
Why do some sizes have no letter?
Not every metric size has a US equivalent; for those, use the mm size printed on the hook or needle.
Sources
- Craft Yarn Council: Hooks & Needles (checked 2026-10-02)
- Craft Yarn Council: Steel Crochet Hook & Crochet Thread Sizes (checked 2026-10-02)
- Wikipedia: Knitting needle (Needle Size Conversions) (checked 2026-10-02)
Last checked: 5 October 2026