Knitting needle sizes: US, mm and UK
Makers number and letter their needles differently, so the millimeter size printed on the needle is the one to trust. US sizes are from the Craft Yarn Council standard. The UK now sizes needles in millimeters. The old UK numbers still appear in older patterns and on some ball bands, and they run the other way: the bigger the number, the thinner the needle. A dash means there is no standard size in that system.
| Metric | US | Old UK |
|---|---|---|
| 1.5 mm | 000 | – |
| 1.75 mm | 00 | – |
| 2 mm | 0 | 14 |
| 2.25 mm | 1 | 13 |
| 2.75 mm | 2 | 12 |
| 3 mm | – | 11 |
| 3.125 mm | 3 | – |
| 3.25 mm | 3 | 10 |
| 3.5 mm | 4 | – |
| 3.75 mm | 5 | 9 |
| 4 mm | 6 | 8 |
| 4.25 mm | 6 | – |
| 4.5 mm | 7 | 7 |
| 5 mm | 8 | 6 |
| 5.25 mm | 9 | – |
| 5.5 mm | 9 | 5 |
| 5.75 mm | 10 | – |
| 6 mm | 10 | 4 |
| 6.5 mm | 10½ | 3 |
| 7 mm | – | 2 |
| 7.5 mm | – | 1 |
| 8 mm | 11 | 0 |
| 9 mm | 13 | 00 |
| 10 mm | 15 | 000 |
| 12.5 mm | 17 | – |
| 12.75 mm | 17 | – |
| 15 mm | 19 | – |
| 19 mm | 35 | – |
| 25 mm | 50 | – |
| 35 mm | 70 | – |
Some US numbers cover two metric sizes, such as US 6 for 4 mm and 4.25 mm. When a pattern gives both, follow the millimeters.
Crochet hook sizes: letters and mm
US hooks carry a letter, a number or both, and makers do not all letter them the same way. The millimeter size is the actual diameter of the hook, so check that.
| Metric | US |
|---|---|
| 2.25 mm | B-1 |
| 2.5 mm | – |
| 2.75 mm | C-2 |
| 3.125 mm | D |
| 3.25 mm | D-3 |
| 3.5 mm | E-4 |
| 3.75 mm | F-5 |
| 4 mm | G-6 |
| 4.25 mm | G |
| 4.5 mm | 7 |
| 5 mm | H-8 |
| 5.25 mm | I |
| 5.5 mm | I-9 |
| 5.75 mm | J |
| 6 mm | J-10 |
| 6.5 mm | K-10½ |
| 7 mm | – |
| 8 mm | L-11 |
| 9 mm | M/N-13 |
| 10 mm | N/P-15 |
| 11.5 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 |
Steel crochet hook sizes
Steel hooks are for crochet thread and lace-weight yarn. Their numbers run the opposite way from regular hooks: the higher the number, the smaller the hook. Makers number them differently, which is why some sizes appear twice.
| Metric | US steel |
|---|---|
| 3.5 mm | 00 |
| 3.25 mm | 0 |
| 2.75 mm | 1 |
| 2.7 mm | 00 |
| 2.55 mm | 0 |
| 2.35 mm | 1 |
| 2.25 mm | 2 |
| 2.2 mm | 2 |
| 2.1 mm | 3 |
| 2 mm | 4 |
| 1.9 mm | 5 |
| 1.8 mm | 6 |
| 1.75 mm | 4/0 |
| 1.7 mm | 5 |
| 1.65 mm | 7 |
| 1.6 mm | 6 |
| 1.5 mm | 8/7/2 |
| 1.4 mm | 9/8 |
| 1.3 mm | 10 |
| 1.25 mm | 9/4 |
| 1.15 mm | 10 |
| 1.1 mm | 11 |
| 1.05 mm | 11 |
| 1 mm | 12/6 |
| 0.95 mm | 13 |
| 0.9 mm | 14/8 |
| 0.85 mm | 13 |
| 0.75 mm | 14/10 |
| 0.6 mm | 12 |
Crochet thread is numbered the same way round: size 3 is thicker than size 30.
Needle and hook size for each yarn weight
The Craft Yarn Council groups yarn into weight categories 0 to 7, and many labels print the number. These are the needle and hook sizes most often used with each one. Your pattern's needle and your gauge swatch come first.
| Yarn weight | Knitting needles | Crochet hooks |
|---|---|---|
| 0 Lace: fingering, 10-count crochet thread | 1.5–2.25 mm, US 000–1 | Steel 1.6–1.4 mm (steel 6, 7, 8); regular 2.25 mm (B-1) |
| 1 Super fine: sock, fingering, baby | 2.25–3.25 mm, US 1–3 | 2.25–3.5 mm, B-1 to E-4 |
| 2 Fine: sport, baby | 3.25–3.75 mm, US 3–5 | 3.5–4.5 mm, E-4 to 7 |
| 3 Light: DK, light worsted | 3.75–4.5 mm, US 5–7 | 4.5–5.5 mm, 7 to I-9 |
| 4 Medium: worsted, afghan, aran | 4.5–5.5 mm, US 7–9 | 5.5–6.5 mm, I-9 to K-10½ |
| 5 Bulky: chunky, craft, rug | 5.5–8 mm, US 9–11 | 6.5–9 mm, K-10½ to M-13 |
| 6 Super bulky: super bulky, roving | 8–12.75 mm, US 11–17 | 9–15 mm, M-13 to Q |
| 7 Jumbo: jumbo, roving | 12.75 mm and larger, US 17 and larger | 15 mm and larger, Q and larger |
So DK yarn usually goes with 3.75 to 4.5 mm needles (US 5 to 7), worsted with 4.5 to 5.5 mm (US 7 to 9), and bulky with 5.5 to 8 mm (US 9 to 11).
Wrong size for your gauge?
If your swatch has more stitches per 4 inches than the pattern, go up a needle or hook size. If it has fewer, go down a size. The gauge calculator shows how far off a different gauge would leave the finished piece, and the yarn calculator estimates how much yarn the project needs.