Crochet Hook Size Converter
Hook sizes use different naming systems around the world, which makes patterns confusing. Convert instantly between millimetres, US letter sizes and UK numbers so the hook in your hand always matches the pattern you are following.
Result will appear here.
How to use
- Enter a value or select an option.
- Choose the From and To units — the result updates live.
- See the converted values in all units below.
Tips
- US letter sizes skip some millimetre steps, so always check the mm column, not just the letter.
- UK steel hooks use a different numbering from UK aluminium hooks - the tool follows the common modern chart.
- When a pattern says 'or size needed for gauge', the hook size matters less than your swatch.
- Keep a tape measure handy: hook stamps can wear off with use.
Note: Some brands differ slightly in US lettering — the mm printed on the hook is always final.