This is a difficult question because it is definitely a matter of personal taste. First of all, you should look for a surgeon who is really going to listen to what you want and not impose their personal taste on your breast size. The next part is communicating clearly what your goals are. I always ask my breast augmentation patients to upload what we call “wish pics” to their consultation app so I can have a better idea of what they are looking for. Cup sizes are a terrible way to talk about breast size, since this is not a standard measurement. We know from going bra shopping that all C cups are not the same. So in this case, pictures are worth a thousand cup sizes.
Assuming now that I know what you want, we are going to see if that is possible based on your body. In your consultation I am going to examine you and take measurements that will let me give you a range of implant sizes that are recommended for your body. Then we will use sizers in a bra to get a sense of what you are happy with in that range of sizes. Sometimes, depending on what you look like to start with, I may recommend you also get a lift, or mastopexy, to get your nipples located at the center of the breast over the most projected part of the implant. This is usually going to be the case if the nipples are located at or below the level of the crease under the breast.
Now, what if you don’t like the sizes that are recommended? If you think you want to go smaller than that range, then I would recommend either not doing the augmentation or else considering something like fat grafting instead of implants. If you want to go bigger than the recommended sizes, that will usually still be possible, but it will put a lot of stress on your tissues, so you will be more at risk for problems like seeing the implants through the skin, having the implants drop too low, or having the implants push up the tissue in between the breasts to create synmastia, or “uniboob.” These problems can be very hard to fix, and the risk goes up the bigger the implant that you choose beyond your recommended sizes.
Some plastic surgeons will say that they will just pick the best size for you during the surgery, but I prefer to have my patients decide on their size before surgery. I want you to be empowered to make your own choices for your body instead of waking up to whatever your surgeon thinks looks the best.