I don't understand if you are currently a B or a D. However, on average, it will likekly take a 400-450cc implant to get you up to a D cUp.
It is very easy to be confused by this measuring system. Cup sizes are only used as estimates for clothing. Although the measuring technique for determining cup size is precise, the results of these measurements are not. Let me give you an example; weight is a very accurate measurement. However two patients that weigh 120 lbs are not likely to look alike. The same is true with two patients that have C cup breasts. This is why physicians tend to use volume (cubic centimeters or cc) as a more accurate measurement. Note: If you are trying to figure out what breast implant size you want to obtain, you can try the szing tool available through b4bra.com or read the articles about measuring there.
Size is a complex decision that is not only based upon your height, weight and current cup/bra size but ALSO on also on your breast diameter, waist, shoulder, and skin envelope measurements. These can only be assessed in person during a consultation. A good place to start is using my "Find your perfect size" tool listed in the left hand column of my bodysculptor.com home page. Another good place to look is the searchable database section of the physicians' photos on implantinfo.com. Best of luck.