The body mass index (BMI) is defined as the body mass divided by the square of the body height, and is universally expressed in units of kg : m2, resulting from mass in kilograms and height in meters.
Example: Weight is 65 kg and height 1,65 meters, therefore: 65 : (1,65x1,65) = 65 : 2,7225 = 23,875 (index is in the range of normal).
Based on calculated index, you can define if person is underweight, normal, overweight or obese.
Underweight- BMI < 18,5
Normal (healthy weight) - BMI = 18,5 – 24,99
Overweight- BMI = 25 – 29,99
Obese - BMI > 30
NB! BMI is used differently for children. It is calculated in the same way as for adults, but then compared to typical values for other children of the same age.