Implant size and placement ? I'm 5'7" and 115 lbs. I measure 13 in. (photos)

Hi.  To appropriately discuss implant size and choice, you really need an in person evaluation by a plastic surgeon with good experience with breast augmentation.  Opinions and preferences will vary somewhat from one surgeon to another surgeon.  Personally I start with the base width of the patient as the starting point for the footprint of the future implant.  Tissue characteristics, and desired postoperative size, and patient anatomy all factor in to the proper selection of implant volume as well as profile.  I go over all of that all in detail with my patients at the time of their consultation.Based on your picture, you appear to have very small amount of breast tissue to start with, and so likely your implants would be placed underneath your muscle.  I am betting that you have a fair amount of space in the middle of the chest between where the muscles attach to your breastbone, and that part is not able to be really changed without creating significant problems.  But the amount of space that you naturally have between where your muscles attach will basically determine how much space is in between your implants, when they are placed underneath your chest muscle.  You can have your plastic surgeon explain that in more detail to you based on an in person examination.
I would recommend consulting with a board-certified plastic surgeon with good experience in this area.  He or she can thoroughly review the options with you so that you can make a good and well-informed mutual decision.
Good luck and take care, Dr. Howell

Hello dear!
Thank you for your question and provided information as well..
Based on your photos, it seems that you have symmetrical breasts for which you wish to add more volume. There are many ways that plastic surgeons perform measurements in order to determine which breast implant size, style and shape will best suit your goals. It is important that you communicate to your board-certified plastic surgeon what are expecting, to make certain that your goals are realistic. It's helpful to show pictures of results you'd like, but please keep in mind that these are other people and your body is different from everybody. In my office, we use a method of sizing with silicone gel forms of known volumes. This is proven to be a very accurate means of determining what size will might be of additional interest to you as well.
Know that the size, profile, and shape of the implant is based on your desired breast size/shape, your chest wall measurements, and soft tissue quality.  This decision should be based on a detailed discussion with equal input from both you and your surgeon.   
Hope this helps and best of lucks.
Dr. Luis Mejia.