I get this question all the time.
The textbook definition is: Body Mass Index (BMI) a measure used to evaluate body weight relative to a person’s height. BMI replaced the height and weight charts insurance companies used.
Here is the issue that some exercise physiologist and personal trainers have with it. If you are someone with a lot of muscle you will have a high BMI. Here’s what I mean. Back in the Arnold Schwarzenegger BMI would have been off the charts. Was he unhealthy or just muscular?
Don’t get caught up in the numbers, see how you feel. Do your clothes fit. Do you have energy. If so then the numbers don’t matter.