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Description: Calculate BMI (Body-Mass-Index)

Calculate BMI (Body-Mass-Index)

In this article, you will learn what the Body Mass Index (BMI) is and how it is calculated. With the help of this value, you can determine whether your weight is too high or too low.

What exactly is the Body Mass Index?

The body mass index, or BMI for short, is a measure with which you can evaluate the body weight of a person in relation to its height. A classification is made from very severe underweight to morbid obesity. Since neighter sex nor age or the physical build is included in the calculation, the value should only be considered as a recommendation. The Body Mass Index is calculated as follows:

$$\text{BMI}=\frac{\text{Body weight in kg}}{(\text{Body height in meters})^2}=\frac{m}{l^2}$$
BMI = (Body weight in kg) / ((Body height in meters)^2) = m / (l^2)

Interpretation of the BMI

For the interpretation of the body mass index, the WHO has defined several categories ranging from very severe underweight to morbid obesity. For adults, the BMI can be classified as follows:

Category BMI
from to
Very severe underweight 15.0
Severe underweight 15.0 16.0
Moderate underweight 16.0 17.0
Slight underweight 17.0 18.5
Normal weight 18.5 25.0
Overweight 25.0 30.0
Moderate obese 30.0 35.0
Severe obese 35.0 40.0
Very severe obese 40.0 45.0
Morbid Obese 45.0

Limits of the BMI

BMI scales

As already mentioned, this index should only be interpreted as a very rough guide, as the BMI only takes into account the total weight and not the actual body fat percentage. For example, people who do weight training and therefore have a high muscle mass, are sometimes classified as overweight, although from a health point of view it is not comparable to a "normal" overweight person who simply has a too high body fat percentage. The gender is also not included in the body mass index, although it is widely known that women tend to have more body fat than men. And age, which is also not included in the calculation, also has a significant impact on a person's body weight.


In conclusion, one can say that the BMI should only be used as a very rought guide for the optimal body weight. Finally, everyone has to know their own physical characteristics and simply develop a feeling for interpreting their own body correctly.

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Posted on 14.11.2018 | Last modified on 02.05.2021