I've been cycling for about 45 yrs. So, when I started it was before sloping TTs. I used the LeMond-Guimard method which is to measure your inseam in CM and multiply it by .665. This puts me in the 54-55 range of traditional frame size. With today's S-M-L-XL sizing you would have to take a virtual TT measurement in order to get BB to TT size. Simply using your height may or may not work since two people of the same height can have significantly different inseams. And, when it comes to measuring saddle height I would encourage you to avoid measuring from the center of the BB since crank lengths differ.