Originally Posted by
Nanomite
Somebody recently posted this link.... If your bored and have a tape measure then try it. I measured my wife using this last night. She is the same height as you and the competitive fit was ~ 47, Eddy fit ~ 49.5 and the relaxed fit (French) ~ 52 which is the largest appropriate frame size.
I'd still go get fitted.
Fit Calculator
Depends on the frame. I am about 5'6.5" and was a 52 on a similar Cannondale Black Lightning. Professionally fitted as a 54 on an '09 madone. Also depends on your proportions.