3 weeks post breast reduction. How long does swelling take to go down? How much should go away?

Hello,
There is certainly swelling still, and your breasts should decrease in size by about 10 to 15% over the next 6 months or so.  Unfortunately, discussing bra sizes as a means of breast goal size is fraught with disappointment due to the non-standardized bra size system as well as the subjective nature of wearing bras.  If you feel that you are still too large after completely healing, then you will need to get a revision breast reduction. Be sure your surgeon is a revision breast specialist. 

Dear jcm23,3 weeks after breast reduction there still can be some postoperative swelling. In most cases, the patient is able to see the final results after a few months when the swelling fully resolves. If you are concerned, I would suggest you to consult a board-certified plastic surgeon.Daniel Barrett, MD, MHA, MS
Certified, American Board of Plastic Surgery 
Member, American Society of Plastic Surgery