Saw him in person at a show a few years back. Got a glimpse of him next to a fighter from our gym that's a solid 6'1. Paul was a touch taller. Maybe 1/2'' or 1'' at the most. I'm 6'4.5- 6'5 and Paul was noticibly shorter than me.
He may also look taller because of how skinny he is. I have a friend who's just as tall as me, but when we aren't next to each other people think he's taller than me. Of course once we measure each other we are equall in height but that's just how perception works. He looks taller because he is skinnier.
6'3" I would say. Calzaghe is 6'1" in reality although he is sometimes listed as 5'11" or 6'. It seems some fighters like to list themselves as shorter than they are.