If I had to guess (and I really don't know), I would think somewhere between 4 1/2 and 5". You're going to be turning it over 1/4", so that takes a half inch and you need to cover it on the back at least 1" on each size, so if you need a 2" finished yo-yo, that would be 4 1/2" right there. I'm interested in what other people say.