What breast size is ideal for my height and weight?

There is not necessarily an ideal breast size for your height and weight though there can be a range depending on a few factors including preferences. You do want to make sure that you are reduced enough to properly address the issues associated with your large breasts. For my patients, I generally recommend going down to the C to D range but realize that because of the proprietary nature of cup sizes, one C bra may fit exactly the same as another company's D bra (and so forth). You should seek a consultation with a board certified plastic surgeon who can discuss this issue with you at length and make recommendations based on several factors including your preferences.Steven Turkeltaub, MD

Ideal breast size is difficult to define, but certainly one of the main goals of the surgery will be removing enough tissue that you have relief of your neck, back and shoulder pain and be happy with your new breast size!  It is nice to balance the chest with the hips.  Most reductions remove about half of the breast tissue and leave behind enough to keep the remaining breast healthy.  At your young age, attention to preserving milk ducts and blood supply is important as well for future possible pregnancies/nursing and maintaining sensation.  Breast reductions change lives!   Discuss the above with your plastic surgeon at your consultation.

For someone like yourself who is taller, having a larger breast size, such as a C/D is not as obvious as it is on someone smaller, however most women I see for breast reductions request something in the C range - whether you go larger or smaller in this depends on what your goals are after surgery. Think about whether you would be more upset if you woke up from surgery smaller than you expected or larger than you expected. Another thing to do that might help is to go to the store and look at bras in your same band size, but in a B, C and D cup. That will give you a pretty good idea what volume you may want your breasts to be after surgery. 

"Ideal breast size" is really a range of size.  It depends on your anatomy, your wishes, what you do for work and play, etc.  I think before and after photos are very useful for patients as long as the before photos is one that looks a lot like you do now.  I like patients to bring these in at the time of consultation.  I also have about a bajillion photos in my photo book I can show patients.  Also, bra sizes are all over the place and I can never guarantee a specific bra size.  It sounds to me like you would benefit a lot from a reduction.  The trade offs would include scars and the likely inability to breast feed a baby.   The scars are where the sun doesn't shine in most swimwear and breast feeding, IMO, is overrated and should not discourage you from looking into a reduction.  It really can be life changing!

I'm afraid it's a misconception to think surgeons can reduce a large breast to fit a specific bra size. I prefer to have patients bring in photos of surgical patients that have a proportionate postop look they find pleasing and then we discuss the surgery in detail and also whether we can  get close to a look that is similar to their goal look IF that is a realistic result for the specific patient. Keep in mind the primary goal is a result that is comfortable.