Finding the right breast implant size is a very personal choice. Depending on your existing breast tissue, the same implant on you could look very different on someone else. As a general rule of thumb, every 150 ccs increases your bra cup 1 to 1.5 sizes.
Factors that change implant sizing:
Your height: A taller person could have a larger implant with it still looking more natural.
Width of your natural breasts and the size of your chest wall: The desired breast fullness and shape partially determine the implant’s size.
Your frame: Women with larger frames and stronger muscles can handle large breast implants. Large implants are heavy and may cause pain in a smaller person. A small-framed person may consider higher profile implants to achieve the look or larger breasts without so much mass.
Lifestyle: For active people, large implants may not be a good idea. Large implants can be heavy and in the way. Also, think about the types of clothes you like to wear and if the breast size will negatively affect their fit.