The body mass index (BMI) is a value derived from the mass (weight) and height of an individual. The BMI is defined as the body mass divided by the square of the body height.
BMI is an attempt to quantify the amount of tissue mass in an individual, and then categorize that person as underweight, normal weight, overweight, or obese based on that value.
Commonly accepted BMI ranges are underweight: under 18.5 kg/m2, normal weight: 18.5 to 25, overweight: 25 to 30, obese: over 30.
However, BMI was designed in the 1830’s as a measurement of population health, and was not intended to work with individuals. Subsequently, users often receive results that do not accurately reflect their general level of obesity or health.