A very important concept is that you do not want to make this decision based on a fear that someone will notice. If you want to go "incognito" wear more conservative clothing for a while. The goal is to look great in a bathing suit and a dress. Many "conservative" people are disappointed later that they didn't go large enough. 

How to choose what is best for you...

I uniformly refuse to quote cup size in my practice. Why?

Bra cup size varies between manufacturers, styles and how you wear your bra. Different style bras fit differently. Some people wear their bra so that they bulge out of the top, others wear it so loosely that you can't  find their breast inside! 

Never look at someone else's choice of implant. It's what you start with--- PLUS what you add--- superimposed upon the shape of your own body. The same size implant may look completely different on another person.

The variation is so great that I have my patients come to the office with a flat panel sports bra and we put different size implants in the bra in front of a mirror. I encourage them to bring bathing suits, dresses, and any other clothing that they like to wear. This really gives you a good idea of what you will look like at each size.

Due to differences in clothing a "C" cup is not always a "C". Looking in the mirror and seeing what you look like 300cc bigger is simple physics! Your present chest plus 300cc has to look very similar to what you will look like with your present chest plus 300cc. 

There is one small difference that I have learned from experience.  When the implants settle, they usually look very slightly smaller.  Therefore, I encourage my patients to pick one size larger then they like in the mirror.  (If you like 350, get 375.)

Most of the implants that are chosen by my patients are between 250cc and 675cc. Some are smaller and some larger. The largest implant available legally today is 1200cc. 

Formulas, standards and comparisons may work in theory, but we all know that if you ask two women with exactly the same size breast what size they are, one may be absolutely certain she is a C while the other is sure she is a D. I don't think that "standards" work!  Breast size is often "in the eye of the beholder!"

 A sports bra holds the implants against your chest like your natural tissue will. "Trying On" the implants in front of a mirror with several different outfits, in my opinion, is the best way to proceed!