I am a 34C. Will 300cc silicone implants bring me up to a D cup?

Breast implant sizes do not correlate to bra cup sizes. The same implant size will look different on each individual person. You should consult with a board certified plastic surgeon and try on implant sizes. I also recommend bringing in a photo to guide your PS on what look you are hoping to achieve.

Hello! Thank you for your question. In general, implant size does not
correlate with bra cup size. The cup size itself will vary from
manufacturer to manufacturer as well as who is doing the actual
measurements. Thus, cup size is never a reliable indicator for your
breast size. I typically encourage my patients not to communicate her
desires in cup size but more on the actual look and appearance.  The increase in size will depend on your preoperative size, chest width, implant type/projection, and height/weight.  However, on cup size increase should be accomplished with that size implant.Good communication between you and your surgeon of
your expectations is warranted - choosing your surgeon wisely is the
first step. Discussion of your wishes and having an honest and open
dialog of your procedure is mandatory (e.g, implant type, incision,
placement, lift, etc). I have found that photographs brought by the
patient is helpful to get a visualization of the appearance you wish for
in terms of size, shape, fullness, etc. Preoperative sizing may be available and helpful to both you and your surgeon.   In addition, your surgeon's
pre and postoperative photographs should demonstrate a realistic goal
for you. Once this has been accomplished, allow your surgeon to utilize
his/her best medical judgment during the procedure to finesse the best
possible result for you after preoperative biodimensional planning and
fitting the right implant for your breast width. Hope me that this helps! Best wishes for a wonderful result!

Thank you for your question.  Without an in-person exam, I would not be able to tell you for sure.  Approximately 200cc will increase your breasts by 1 cup size.  The best thing to do to determine what size is best for you and will give you the results you're wanting, is to go in for a consultation with a Board Certified Plastic Surgeon and try on the implants.If you would like more information regarding breast augmentation, you can download a free copy of my Breast Augmentation Planner.  It has more than 30 pages of valuable information to help you through this process, you can download your copy at aBetterBreast.com.  Best of luck to you!