How Long After Breast Augmentation Surgery, Will I Be my Final Bra Size?

You are only 1 month out of surgery and I would tell my patients to wait before buying bras because in my experience, things still change for the first 3-6 months (each pt is different). Don't buy all of your bras just yet, wait a few more months.

Patients undergoing breast augmentation can anticipate significant swelling in the immediate post-operative period. This swelling resolves quickly with the vast majority being gone in about three weeks. Almost all of the visible swelling is gone in 4 to 6 weeks, but small amounts of residual swelling may be present for up to 3 to 4 months following surgery. For these reasons, it's appropriate to assume that you've reached your final bra size three months following your procedure.

I feel 3 months is a good time frame for all the swelling to be gone and try on some sample bras. Healing can be as short as a month.