Free tool
Hook size converter.
Type a size in any system. The other two fill in automatically, with example yarn weights. Use the metric marking when letter or number labels are ambiguous.
Popular sizes
Your conversion5.0 mm · US H/8 · UK 6Best for yarn weightWorsted (CYC 4)
How it works
- Type a size in any of the three fields. The other two fill in automatically.
- Metric (mm) is the universal standard. When a pattern lists a US letter or UK number, the mm value is the one to trust.
- If two systems share the same number (like mm 6.0 and UK 6), type into the field for the system you actually have.
- The yarn weight at the bottom tells you what kind of yarn works best with that hook.
Full hook size chart
| Metric | US | UK | Common Yarn |
|---|---|---|---|
| 2.25 mm | B/1 | 13 | Fingering / Sock (CYC 1) |
| 2.75 mm | C/2 | 12 | Sport / DK (CYC 2) |
| 3.25 mm | D/3 | 10 | Sport / DK (CYC 2-3) |
| 3.5 mm | E/4 | 9 | DK / Light Worsted (CYC 3) |
| 3.75 mm | F/5 | 9 | DK / Light Worsted (CYC 3) |
| 4.0 mm | G/6 | 8 | Worsted / DK (CYC 3-4) |
| 4.5 mm | 7 | 7 | Worsted (CYC 4) |
| 5.0 mm | H/8 | 6 | Worsted (CYC 4) |
| 5.5 mm | I/9 | 5 | Worsted / Bulky (CYC 4-5) |
| 6.0 mm | J/10 | 4 | Bulky (CYC 5) |
| 6.5 mm | K/10.5 | 3 | Bulky (CYC 5) |
| 7.0 mm | 7mm | 2 | Bulky (CYC 5) |
| 8.0 mm | L/11 | 0 | Super Bulky (CYC 6) |
| 9.0 mm | M/N-13 | 00 | Super Bulky (CYC 6) |
| 10.0 mm | N/P-15 | 000 | Super Bulky (CYC 6) |
| 12.0 mm | P | — | Super Bulky / Jumbo (CYC 6-7) |
| 15.0 mm | P/Q | — | Jumbo (CYC 7) |
| 16.0 mm | Q | — | Jumbo (CYC 7) |
| 19.0 mm | S | — | Jumbo (CYC 7) |