The percentage of fat transfer that becomes permanent depends largely on the area grafted and the techniques used to graft it.  It can range from 20-40% in the face to 80% or more in the buttocks (such as with the Brazilian Butt lift) if the procedure for fat grafting is the ‘micro fat graft technique’

However you will usually know within 4 months what your final results will look like. As with any procedure, discuss your goals with a Board Certified Plastic Surgeon to decide the best course of action for your specific needs and choose a surgeon skilled in fat grafting procedures.