Dr.what is normal breast size of a 19year old girl?

Depends!: Breast size, like penis size, depends upon individual. While there is some association w/age, there is no specific "normal" for any given age. Instead, we assess pubertal development by tanner stages. In theory, breast should be tanner stage v by 15yo which is described as "breast reaches final adult size; areola returns to contour of the surrounding breast, with a projecting central papilla".

It varies widely: ...So there isn't a standard value or cup size i can give you. Sorry.