Reference / Hook conversion
Crochet hook size chart: US, metric, and UK.
Find the millimetre equivalent first, then use the letter or old UK steel number as a helpful cross-check. A swatch is still the final answer.
Conversion chart
Use millimetres as the common language.
Letter labels differ across brands and old UK steel sizes are mainly useful for smaller hooks. The metric measurement is the most reliable way to match a pattern.
| US label | Metric size | UK old steel | Typical starting use |
|---|---|---|---|
| B-1 | 2.25 mm | 13 | Thread / lace |
| C-2 | 2.75 mm | 12 | Fine |
| D-3 | 3.25 mm | 10 | Light |
| E-4 | 3.50 mm | 9 | DK |
| F-5 | 3.75 mm | — | DK |
| G-6 | 4.00 mm | 8 | DK / light worsted |
| 7 | 4.50 mm | 7 | Worsted |
| H-8 | 5.00 mm | 6 | Worsted |
| I-9 | 5.50 mm | 5 | Worsted |
| J-10 | 6.00 mm | 4 | Bulky |
| K-10½ | 6.50 mm | 3 | Bulky |
| L-11 | 8.00 mm | 0 | Bulky |
| M/N-13 | 9.00 mm | 00 | Super bulky |
| P/Q | 15.00 mm | — | Jumbo |
What size hook should a beginner use?
A 5.00 mm H-8 hook with light-colored worsted yarn is a practical place to learn basic stitches. Follow the yarn label or pattern if one is provided.
Why can the same letter vary?
Manufacturers do not all use the same letter ranges. If a hook says both a letter and millimetres, trust the millimetres for matching gauge.
Hook size changes fabric.
A larger hook generally creates a looser fabric; a smaller hook makes a denser one. Measure your swatch before changing a pattern's size.
Continue your project planning
Use the gauge and starting-chain calculator after choosing a hook, then print the hook size chart or keep the project planner beside your yarn.