BMI stands for Body Mass Index. It is a measure of body fat based on a persons weight and height. The BMI is calculated by dividing a person's weight in kilograms by the square of their height in meters. The resulting number is then used to classify a person as underweight, normal weight, overweight, or obese based on established BMI categories. The BMI is a convenient rule of thumb used to broadly categorize a person's weight status based on tissue mass (muscle, fat, and bone) and height. The BMI is a reliable indicator of body fatness for most people and is used to screen for weight categories that may lead to health problems. However, it is important to note that the BMI is a screening measure and is not intended to diagnose disease or illness. Additionally, the BMI may not be accurate for certain individuals, such as athletes or those with a high muscle mass, as muscle is denser than fat.