I'm about as average as they come. 5'6", 31ish inseam, maybe? My current bike is a 54 and the measurements I have from it seem to match best (barring differences you'd expect between a touring bike and road bike) with the men's medium.

Of course it's way more bike than I ever thought about getting, but man, to only spend $800 of my own money on a bike like this? I'd be bordering on stupid to pass it up.

Sarah