What should I expect my cup size to be after 325 cc implants? Currently an A cup

There is no standard bra cup-sizing system.
“C cup” can mean one thing if it’s made by Victoria’s Secret and another if it’s made by Vanity Fair. You might need a B cup in a full-coverage bra and a C cup in a demi bra, even if the same company makes both styles. Your cup size is also affected by how tight you make the band. If you wear it tighter, it will push your breasts deeper into the cup and you’ll need a bigger cup size.
What looks proportional varies from person to person.
Think of “proportional” as a “C look” rather than a “C cup.” To achieve the C look, a 5-foot woman with a small frame might only need a B cup while a 5-foot-8-inch woman with a large frame might need a D cup. Dr. Ted Eisenberg, Board Certified Plastic Surgeon and Author. RealSelf Distinguished Hall of Fame Inductee. Philadelphia, Pa., USA

Dear a.swede.with.questions,
breast implant type and sizing selection is a complicated process and requires a detailed consultation that includes a discussion of your goals, a detailed examination, and a lengthy discussion. But the decision will always start and end with the patient. When it comes to sizing, we have all of our patients find 3 photos of their desired breast size. We ask for naked breast photos because clothing can obscure the true size (push up bras). Next, we consult with patients and go over the photos and take detailed breast measurements during a physical exam. Next, we using a sizing algorithm to determine a range of implants that will work based on the exam and the measurements.Lastly, during the operation, we use silicone sizers in the operating room to see how the size actually looks in the breast. We sit the patient up in the operating room, while asleep of course, and compare the sizer result with their desired look photos. If it is too small, we start the process over with a slightly larger implant. We don't stop until we get the perfect match.Of all of my breast augmentation patients, every one of them has been happy with their size due to this detailed and meticulous process. You don't want to invest time and money into a result that is either too big or too small.You should discuss your concerns with a board-certified plastic surgeon and make sure that your surgeon understands your goals.
Daniel Barrett, MDCertified, American Board of Plastic SurgeryMember, American Society of Plastic SurgeryMember, American Society of Aesthetic Plastic Surgery

It's difficult to accurately predict cup size with a given implant as these can vary by manufacturer. Based on the information provided you should be in the C/D range after augmentation. Many surgeons have sample implants that you can "try on" to give you an idea of how you may look after surgery. This may guide you with implant selection. I've included a video that I hope you find helpful.