Once you decide to undergo breast augmentation, in my opinion the concept should be to find the implant size that produces the size of breasts that you want - by that I mean how the breasts look on your body, not the cup size. Then after your surgery when your breasts have healed, get a formal sizing done, and whatever cup size you fit at that point is the cup size that you wear. What does it matter as long as your breasts look good on your body; you just need the appropriate size of bra to fit them, not the other way around. You do this by going to a surgeon that has the ability to perform a proper preoperative sizing exercise on you to determine the optimal size of breast implants to meet your goals. There is also much variability in how different manufacturers cut and assemble their bras, and therefore, you may wear a C cup in one brand of bra and a D cup in another. Furthermore, cup size is really a measure of proportion, thus it is a relative measurement between the breasts and the chest, and although the fit may not be perfect, this explains why a lady might fit into a 34 B as well as a 36 A. For these reasons the best place to start is by "picking" the breasts that you want, and then once you have those, you go out and find the clothing that fits them - bras, bathing suits, etc. Not the other way around. Good luck.