Based upon your height and weight, you seem to have an medium body frame. Several factors go into choosing the best implant size for an individual woman. These include the height and weight as well as the dimensions of the chest, and the quality of your chest wall tissues.
Larger chest wall dimensions can accommodate larger implants. In general, as breast implant size increases so does the diameter of the implant. A breast implant that is too small or too large will not give a nice cosmetic result. During my consultations, I measure the chest wall dimensions and suggest implants in the right size range. I also let women try on different sized implants in a bra to give them an idea of the shape they can achieve with various sizes and styles of implants. I think the women find this very helpful in choosing an appropriate size for their frame.
The tissue quality of your breasts, skin and muscles are also very important. A woman with very tight tissues usually cannot accommodate very large implants. On the other hand, a woman with looser tissues can have larger implants. The tissue quality can be assessed by your consulting physician,
Another issue which you did not mention, is the implant style. High, moderate and low profiles all have slightly different dimensions. High profile implants have a narrower diameter for a given volume. Moderate and low profile implants have a wider diameter and may be better for women with wider chest walls. High profile implants also tend to create more fullness in the upper part of the breast.
Your doctor can help you choose the right size and style based upon your physical exam and the shape you are seeking.