I agree that there is no "standard volume implant" just as there is no standard dress size or shoe size. I disagree that there is "no reliable way to predict" size. I also do not find that external sizing methods, variations in stuffing bras, is at all helpful.
It is important to understand that there is no reliable or objective method to measure size of the breast before or after the augmentation procedure. Talking cup sizes relative to the chest circumference is the only current way to talk about breast size and it's far from consistent or reliable.
Using measurements (like fitting for a dress or shoe), the way to achieve size predictably is to measure the width of the breast across the center and use an implant that is the same width minus .75 to 1 cm so that it is certain the implant will fit properly behind the breast. If that implant is a high profile volume implant scaled for width like the Allergan Natrelle type saline implants, then the volume of that implant should make the breast look about two cup sizes larger (unless the width of the breast is unusually narrow or wide for the chest width -- women with wide or narrow breasts know this because store-bought bras don't fit them).
If you look like a mid A cup in a 34 inch chest then an Allergan high profile implant matched to your breast width should make you look like a mid C cup in a 34 inch chest. There are other issues to consider such as the degree of droop to the breast but in general that's how size works. The cc's of volume are determined by the width of the implant and its profile.
Low profile implants (saline-Allergan, gel-Mentor and Allergan) should increase the look by a cup size. Medium profile implants (saline-Mentor and Allergan, gel-Mentor and Allergan) should make the breast look about a cup and a half larger. High profile implants (saline-Allergan, gel-Mentor and Allergan) make the breast look about two cup sizes larger. Mentor also has a saline implant that is between a medium and a high profile volume, called a Moderate Plus. Mentor's high profile saline implant is not scaled for width.
