There are many BMI calculators on the internet. Most surgeons prefer to have the BMI be less than 30 to reduce the risk of complications.
I think the standard for most Board Certified Plastic Surgeons is nothing over 30 BMI. I also saw that the other surgeons on this website suggested the same thing but maybe just a little more reassurance that you are receiving the most accurate information is important. It is great that this issue is one of your concerns. Knowledge is very important before making an important decision to have plastic surgery. Good Luck!