I think it just depends upon the method that you'll be using to make socks. I know that if you're using circulars you can use either 2 circs or 1 and do ml. The book that I had gotten to learn how to make two socks at once(which I have yet to try lol) recommended 40" circs, but I'm not sure if the same go for just mling one sock. Either way good luck!!