Knitting needle and crochet hook sizes
Use the millimetre diameter as the common measure. A US 8 knitting needle is commonly 5 mm; a US H-8 crochet hook is also commonly 5 mm. The number alone does not identify the tool.
Knitting needles
| Metric diameter (mm) | Common US label |
|---|---|
| 2 | 0 |
| 2.25 | 1 |
| 2.75 | 2 |
| 3 | — |
| 3.25 | 3 |
| 3.5 | 4 |
| 3.75 | 5 |
| 4 | 6 |
| 4.5 | 7 |
| 5 | 8 |
| 5.5 | 9 |
| 6 | 10 |
| 6.5 | 10½ |
| 7 | — |
| 8 | 11 |
| 9 | 13 |
| 10 | 15 |
| 12.75 | 17 |
| 15 | 19 |
| 19 | 35 |
| 25 | 50 |
Regular crochet hooks
| Metric diameter (mm) | Common US label |
|---|---|
| 2.25 | B-1 |
| 2.75 | C-2 |
| 3.25 | D-3 |
| 3.5 | E-4 |
| 3.75 | F-5 |
| 4 | G-6 |
| 4.5 | 7 |
| 5 | H-8 |
| 5.5 | I-9 |
| 6 | J-10 |
| 6.5 | K-10½ |
| 8 | L-11 |
| 9 | M/N-13 |
| 10 | N/P-15 |
| 15 | P/Q |
| 16 | Q |
| 19 | S |
UK knitting needles: 2–8 mm
In this older numbering system a smaller number means a larger needle. A UK 8 needle is 4 mm, not the 5 mm of a common US 8. This table is for needles, not UK crochet hooks.
| Metric diameter (mm) | UK needle number |
|---|---|
| 2 | 14 |
| 2.25 | 13 |
| 2.75 | 12 |
| 3 | 11 |
| 3.25 | 10 |
| 3.75 | 9 |
| 4 | 8 |
| 4.5 | 7 |
| 5 | 6 |
| 5.5 | 5 |
| 6 | 4 |
| 6.5 | 3 |
| 7 | 2 |
| 7.5 | 1 |
| 8 | 0 |
Resolve an ambiguous label
Some manufacturers use a letter or number for more than one metric diameter. For example, US 6 needles can be marked 4 or 4.25 mm, and US G hooks can be 4 or 4.25 mm. Read the metric marking on the actual tool rather than treating this common-size table as a manufacturer guarantee.
Historical UK numbers and steel-hook numbers run differently from modern regular-hook labels. For sizes outside this UK table, or an old tool without a metric marking, measure the shaft with a suitable gauge or consult its manufacturer’s conversion table.
Compare your measured gauge with the pattern. Matching tool size alone does not make two people’s tension identical.