Originally Posted by mathwizard
Since the pattern is in UK terms then I am going to assume the hook size they refer to is in mm and the American size hook for a 3mm would be a "C" hook and it will probably give you the gauge you need. Pattern directions in UK then hook size in UK also. Try the C hook and see what happens.
I haven't seen any size C crochet hooks. That's why I recommented a size 1 steel hook 2.75 mm where as D is 3.25 mm. (well, those are Boye sizes in mm) I see Susan Bates has different mm sizes for these letters and numbers.
So if your hooks are Susan Bates, then C is 3 mm and a Bates steel hook size zero "0" is 2.55 mm.
Prinmel, are you using Boye hook, size D (3.25mm) and getting 4.72 inches (12 cm) or another brand of hook?
Aside from that, yarn weight might be part of the issue, no?