Body mass index (BMI) is a measurement used to determine the body fat of an individual based on their weight in relation to their height. It applies to most adults over 20.
As you have read, this formula only accounts for weight. However, we know there can be two 200 lb, 6’1″ people that look extremely different. With this being said, they have the same BMI. For this reason, you have to be honest with yourself, and predetermine which category you think you should be in.