What size at an estimate would I be going from a 36DD with 500cc to 800cc?

It is very difficult to determine the best size you will need (recommended based on your photos) or the exact size and shape implant you will require to best match your ideal breast image without an examination by a board certified plastic surgeon. Not just any board certified plastic surgeon, but one with many years of frequently performing breast augmentation surgery including different approaches, techniques and implant choices. This is because several measurements not to mention your breast characteristics are needed to determine the optimal implant size to obtain your goals. Without knowing these dimensions it would be difficult to make this determination. For example, the existing base width of your breast will determine, in many cases, the maximal volume per implant profile that you can accommodate. To illustrate; a 100 cc difference may make a significant difference with a narrow base width breast, but much less of a difference if you have a wide chest wall and wide breast “foot print”. Therefore, just because your friend may have a great result with let’s say a 300 cc implant to make her go from a “A” cup to a “C” cup size does not mean that you will have the same result with the same size implant. The same process goes for just filling in the upper part of your breast without becoming much larger. Further simply placing implants in a bra to determine the size best for you is not always accurate as the bra often distorts the size, is dependent on the pressure the bra places plus the implant is outside your breast and not under it among other variables. Computer software morphing programs that automatically determine the best implant size can be helpful in some but not all cases (e.g. doesn’t work well in my experience with existing implants, sagging or asymmetric breasts). Using “want to be” photos however are useful if simply provided to the surgeon as I will further explain in the link below including silicone vs saline implant
 #breastimplant

Yes, it is possible to #increase your implant size with a #revision. However, the #pocket will need adjustment and a lift may be necessary; to better #support the new implant. Additionally, a mesh for further support may be helpful depending on the #implant size and skin #elasticity. Breast revision surgery is more difficult, complicated, and requires more time than primary surgery. There is as much as a 40% chance additional surgery will be needed following the #revision. 
As far as sizing, there are no promise or guarantee of the specific cup/bra #size and shape you will be after your surgery.  Implants which are under the muscle or are placed in a new position under the muscle may change with shape on muscle #contracture and may have “#banding” and motion of the implants with muscle contracture. If this is unsatisfactory, it may require additional surgery which will also require additional surgeon’s fees, operating room and anesthetic fees.

Whilst it is nice to have larger boobs, it is equally important for them to look as natural as possible. As a general rule, the larger the implant, the harder it is to hide them. One should also take in to account the weight of the implants. The larger the implants, the heavier they will be and this can have adverse effects on your breast envelope. The breast can end up being droopy with a stretched skin envelope in future if the implants are heavy. This may necessitate reducing the volume of the implant and doing a breast uplift procedure in future.

There is a reason why most surgeons you have approached will not place too large implants and even 800cc implants are too big for your chest if you have a bra band with of 36. For optimal outcome, please consult a fully qualified plastic surgeon, who has specialist qualification in plastic surgery 'FRCS Plast' after having being trained adequately in the field of plastic surgery, is registered on the 'Specialist register for Plastic surgery' with the General Medical Council and has been considered competent enough to be a member of the 'BAPRAS' (British Association of Plastic Reconstructive and Aesthetic Surgeons) and 'BAAPS' (British Association of Aesthetic Plastic Surgeons) at the least.

Hi Lauren,It is very common for patients to want an idea of the cup size that they are likely to achieve, but it is notoriously difficult.  Unfortunately, bra cup size is all that we have to go on, so it is natural for us to talk about breast size in this way, but it is very difficult to predict the final cup size.You can get an idea of what the extra 300cc would feel like in your bra by trying on a 300cc sizer in the clinic.  However, it is also important to consider the dimensions of the implant as this is often overlooked by patients.  If you are going from 500cc to 800cc but keeping the same shape and profile of implant, then it will be bigger in every dimension (width and projection). If you are changing the shape and/or profile of the implant (ie going from teardrop to round or from high to extra high), then the extra volume may be more obvious in the projection (maintaining a similar width) and this will have more of an effect.I have just read this back to myself and I know it might sound a bit confusing, but the bottom line is that it is difficult to predict cup size and you need to choose an implant that will fit the dimensions of your breast and give you the sort of look you are trying to achieve.  Good luck!

Thank you for the question.   There is no accurate/reliable/predictable correlation between size/profile breast implant utilized and cup size achieved. For example, I do not think that the generalizations of "200 cc equates to 1 cup" hold any validity or are helpful in any specific or practical way.  In my practice, I ask patients not to communicate their goals, or evaluate the outcome of the procedure performed, based on cup size references.Ultimately,  careful selection of your plastic surgeon and careful communication of your goals (in my practice I prefer the use of goal pictures, direct examination/communication in front of a full-length mirror, and computer imaging) will be critical.
Generally speaking, the best online advice I can give to ladies who are considering revisionary breast augmentation surgery is:
1. Concentrate on choosing your plastic surgeon carefully. Concentrate on appropriate training, certification, and the ability of the plastic surgeon to achieve the results you are looking for. Ask to see lots of examples of his/her work.
2. Have a full discussion and communication regarding your desired goals with your plastic surgeon. This communication will be critical in determining breast implant size/type/profile will most likely help achieve your goals. 
In my practice, the use of photographs of “goal” pictures (and breasts that are too big or too small) is very helpful. I have found that the use of words such as “natural” or "up a cup size or two” or "G cup" etc means different things to different people and therefore prove unhelpful.
Also, as you know, cup size varies depending on who makes the bra; therefore, discussing desired cup size may also be inaccurate. 
3. Once you feel you have communicated your goals clearly, allow your chosen plastic surgeon to work with you in determining the best plan to achieve your goals.
I hope this, and the attached link (dedicated to larger   breast augmentation surgery concerns), helps. Best wishes.