I am 5ft tall and 10 stone (140 lbs). I'd like to know what size my breast on average should be. I currently measure 34GG.

I'm sorry to hear about the problems your disproportionately large breasts cause. Based on your description, you may be a good candidate for breast reduction surgery. This operation tends to be one of the most patient pleasing operations we perform.  When the time is right, I would suggest that you seek consultation with well experienced board-certified plastic surgeons who can demonstrate significant experience achieving the types of outcomes you will be pleased with. Then it will be important that you communicate your goals clearly with your plastic surgeon and make sure that you have realistic expectations prior to proceeding with any type of surgery. In regards to breast size desired, also communicate carefully. In my practice the use of goal pictures are helpful in this regard; a discussion of cup size can be confusing and imprecise. Therefore, I would not suggest that you communicate your goals and/or base your satisfaction with the outcome of surgery on achieving a specific cup size.  For example, a "C or D cup" may mean different things to different people.  I also find that the use of pictures is more helpful than the words “natural” or "proportionate” etc., which can (again) mean different things to different people. Many of my patients choose to have enough breast tissue removed to help alleviate symptoms while retaining enough breast tissue to remain proportionate to the remainder of bare torso. Again, preoperative communication will be critical.   I hope this, and the attached link, helps. Best wishes.

as ideal breast size is purely a personal choice/decision.  Average bra cups are thought to be C cups.  You sound like you could benefit from a reduction but a reduction cannot guarantee a cup size.  It can only guarantee that you will be smaller.  You can help direct your surgeon with requests to be aggressive, conservative, or the usual in your resections.

Thank you for your question and size is an individual decision though most patients wish to be a C or D after a reductionDr Corbin

That is an excellent question!  In my opinion, at 5 ft. tall you should be fine with a C or D breast cup.