Bodies and frames vary a lot. I'm shorter than most of you at only 5', but I have a 29" inseam, which seems closer to some of you that are a lot taller. Even so I still ride a very small bike, since I need the really short top tube. My 700c road bike is a 44cm and the 650c frame I'm getting is a 47cm, the 650c TT bike I picked is a 48, but has the shortest top tube of all my bikes (yes I'm starting to feel like I might have too many...).