As a result of innovation, yarn trends and globalization, the variety of hook and needle sizes and the materials with which they are made has grown over the years. U.S. needle and hook manufacturers continue to use both numbers and/or letters as well as metric sizing (millimeter/mm) on hook and needle packaging. Because letter and number sizing vary from company to company, rely on the package millimeter (mm) sizing, which is an accurate measurement.
Regardless of the number, letter or millimeter sizing, always complete a gauge swatch and compare it to the pattern gauge information. If your swatch is larger than the pattern gauge, redo a swatch using a smaller hook or needle. Conversely, if your gauge swatch it too small, redo it using a larger hook or needle to obtain the gauge indicated in the pattern.
Knitting Needle Sizes
| Millimeter Range | U.S. Size Range |
|---|---|
| 1.50 mm | 000 |
| 1.75 mm | 00 |
| 2 mm | 0 |
| 2.25 mm | 1 |
| 2.75 mm | 2 |
| 3 mm | |
| 3.125 mm | 3 |
| 3.25 mm | 3 |
| 3.50 mm | 4 |
| 3.75 mm | 5 |
| 4 mm | 6 |
| 4.25 mm | 6 |
| 4.50 mm | 7 |
| 5 mm | 8 |
| 5.25 mm | 9 |
| 5.50 mm | 9 |
| 5.75 mm | 10 |
| 6 mm | 10 |
| 6.50 mm | 10 ½ |
| 7 mm | |
| 8 mm | 11 |
| 9 mm | 13 |
| 10 mm | 15 |
| 12.50 mm | 17 |
| 12.75 mm | 17 |
| 15 mm | 19 |
| 19 mm | 35 |
| 25 mm | 50 |
| 35 mm | 70 |
Crochet Hook Sizes
| Millimeter Range | U.S. Size Range |
|---|---|
| 2.25 mm | B-1 |
| 2.50 mm | |
| 2.75 mm | C-2 |
| 3.125 mm | D |
| 3.25 mm | D-3 |
| 3.50 mm | E-4 |
| 3.75 mm | F-5 |
| 4 mm | G-6 |
| 4.25 mm | G |
| 4.50 mm | 7 |
| 5 mm | H-8 |
| 5.25 mm | I |
| 5.50 mm | I-9 |
| 5.75 mm | J |
| 6 mm | J-10 |
| 6.50 mm | K-10 ½ |
| 7 mm | |
| 8 mm | L-11 |
| 9 mm | M/N-13 |
| 10 mm | N/P-15 |
| 11.50 mm | P-16 |
| 12 mm | |
| 15 mm | P/Q |
| 15.75 mm | Q |
| 16 mm | Q |
| 19 mm | S |
| 25 mm | T/U/X |
| 30 mm | T/X |