I ride 50cm and 52cm bikes and I'm 5'7 with 30.5in inseam
they both have around a 53cm top tube.
catch with my fit is that I seem to have longer than average femurs and bikes in this size have steep seat tube angles, so I tend to require 28~32mm of setback from the seatpost to get a proper fit.
what's important is seat tube angle, top tube length and head tube angle.