​I'm 5'3 and 115 lbs, how big should I go for my Breast Augmentation?

When you buy a shoe you should get the shoe that fits your foot, same for breast implants. Let your surgeon give you a narrow range for your anatomy

Thank you for the question. Ultimately, careful communication of your goals, careful measurements (dimensional planning),  careful selection of appropriate breast implants and skillful execution of the procedure will be important steps in achieving your goals.
 
Generally speaking, the best online advice I can give to ladies who are considering breast augmentation surgery ( regarding breast implant size/profile selection) is:

1. Concentrate on choosing your plastic surgeon carefully.  Concentrate on appropriate training, certification, and the ability of the plastic surgeon to achieve the results you're looking for. Ask to see lots of examples of his/her work.

2. Have a full discussion and communication regarding your desired goals  with your plastic surgeon. This communication will be critical in determining  breast implant size/type/profile will most likely help achieve your goals.
In my practice, the use of photographs of “goal” pictures (and breasts that are too big or too small) is very helpful. I have found that the use of words such as “natural”  or “full C or small D cup” etc means different things to different people and therefore prove unhelpful.
 Also, as you know, cup size varies depending on him who makes the bra; therefore, discussing desired cup  size may also be inaccurate.

The use of computer imaging technology may also be helpful to patients;  this technology allows patients to visualize what their breasts may look like with different sizes/profiles of breast implants. I have found this modality to be a nice addition to the communication “tools” available.
3.  Once you feel you have communicated your goals clearly,  allow your plastic surgeon to use his/her years of experience/judgment to choose the breast implant size/profile that will best meet your goals.  Again, in my practice, this decision is usually made during surgery.

I hope this (and the attached link) help.