How much smaller can a waist become in inches after a BBL?

Hello dear!!
Thanks for the question and provided information as well.
Unfortunately, without pictures, it is very difficult to give you a proper answer. l recommend you to make an appointment with a board certified plastic surgeon to talk about your goals and anything you need to know.
Good luck :)

Greetings. In general, the waist size will decrease. This is variable from person to person. The amount of liposuction performed and the degree of post-operative skin contracture also play a role. The best option would be to discuss this with a plastic surgeon. Good luck!