Needles are confusing.
So I cast on with Crystal Palace dpns, size 1 1/2 (2.5 mm) because that was the only size my LYS had in stock at the time. I thought, how much difference can a 1/4 of a mm make? I'm using Koigu for now, by the way.
Working on the ribbing, I decided that it was a little too loose for a sock. So I thought I'd try casting on with my Addi circulars in size 1. Lo and behold, the package says that Addi 1's are also 2.5 mm. Is that right? How can US sizes not even be standard? They seem thinner than the dpn's, but I doubt I can judge a 1/4 mm.
Now I don't know what to do. Maybe Koigu is too thin to use with 1's? I don't know. The mysteries of making socks fit gives me a headache for some reason...But then, I had also wanted to make Eunny's entrelac socks from the new Interweave, and those use Koigu with size 1's. Bleargh. I suppose this explains why my Jaywalker sock turned out a little loose, too. I am so disillusioned! ;)