Can you please explain bmi and what does it calculate?

BMI: Stands for body mass index, it is a ratio of the weight compared to the height and helps doctors to see if patients are in normal weight range, overweight or obese.

Weight:height.: The BMI is simply your weight with respect to your height - an overly simplistic and thereby essentially flawed assessment of your health. It's a bit better when used in combination with body fat measurement. That being said, a high BMI might be associated with diabetes and heart disease amongst other health conditions.