The body mass index (BMI)

Can help you to correctly interpret your body weight. A simple calculation provides information about your body weight and whether you should lose a few kilos.

Whether you are normal weight, underweight or overweight can be easily calculated with the BMI calculator.

The body mass index, BMI for short, helps you to estimate your own weight correctly.
What is a normal BMI for an adult? The Body Mass Index (BMI) relates body weight and height.

What is the Body Mass Index (BMI)?

The body mass index, or BMI for short, is the most common formula for assessing body weight. The ratio is calculated by squaring the body weight in kilograms and the height in metres.

The German Nutrition Society (DGE)

distinguishes between these five categories for the evaluation, depending on the level of the calculated value: Underweight, normal weight, overweight, extreme overweight (obesity) and massive obesity.

BMI = body weight: (body height)²

Example: A man who is 30 years old, weighs 80 kilograms and is 1.85 metres tall has a BMI of 23.37 and is therefore of normal weight.

You can use the BMI calculator to test whether your weight is in the green zone. The link to the body mass index (BMI) also takes age into account and is based on the classic calculation formula.

Body mass index (BMI) depends on age

In addition to weight and height, age must also be taken into account in order to obtain an estimate of one's own weight.

Since normal weight shifts with age, age is relevant. Metabolism and body composition change from the age of 40. As a result, we gain weight and the recommended BMI value changes.

In old age, people increasingly lose muscle mass, which is heavier than fat. Therefore, body weight can decrease again with advancing age. The BMI can falsely indicate underweight, although older people have a normal body weight for this reason.

Is there an optimal weight? Overweight is usually determined by the body mass index (BMI).
The Waist-to-Height Ratio is the ratio between waist circumference and body height. Compared to the Body Mass Index (BMI), it is supposed to provide a better statement about the distribution of body fat.

Why is the Body Mass Index | BMI only conditionally meaningful?

Body Mass Index (BMI) for male & female athletes

The BMI guideline is not without weaknesses. Apart from the fact that age and gender are not taken into account, the BMI is criticised mainly because it only uses weight as an indicator of health and does not distinguish between fat and muscle mass. The BMI simply does not distinguish between muscle and fat.

But BMI alone does not tell the whole story. Athletes, for example, with a BMI of 26 are not overweight, but have a lot of muscle mass. The BMI is also not easily applicable to particularly tall or short people. The BMI also changes with increasing age.

However, BMI is a quick and easy way to categorise your body weight. In addition to BMI, abdominal circumference seems to be particularly helpful in better assessing the health risks of being overweight, according to new scientific data.

People who say "I'm fat" usually see it subjectively, because often people with a normal weight also feel that way. You can find out whether you should really lose a few kilos thanks to the BMI calculator.

The range of medical normal weight (BMI 18.5 - 24.9) is quite wide. For example, for a 1.70 m tall person, it is between 53.5 and 72 kilograms. So you notice: a healthy figure does not mean being super slim. At an older age, the normal weight may also be slightly above a BMI of 25.

Various calculations also give an indication of the desirable BMI depending on age and sex, e.g. the one of the National Research Council below:

This is what you should know about the body mass index (BMI). For endurance and top athletes, the body mass index has only limited significance.

Body Mass Index | BMI Table

The body mass index is used to classify people into normal weight, overweight and obese. The most common table, which is also often used in research, is the WHO table of the World Health Organisation, which is also used by the German Nutrition Society DGE.

Body Mass Index | WHO/DGE:

Meaning BMI

Normal weight 19-24.9

Overweight 25-29.9

Obesity / obesity grade I 30-34.9

Obesity/obesity grade II 35-39.9

Obesity / obesity grade III ≥ 40

Neither gender nor age are taken into account here. The BMI formula only requires height and weight. That is why there are other classifications. For example, the National Research Council (NRC) published a table of normal BMI ranges by age as early as 1989.

Body Mass Index | NCR:


19-24 19-24

25-34 20-25

35-44 21-26

45-54 22-27

55-64 23-28

Ab 65 24-29

The WHO BMI table is mainly used in practice. It is now known that a slightly higher BMI has a positive effect on health and life expectancy with increasing age.

Round and healthy: the BMI is too strict

A few years ago, the WHO used the BMI to set a maximum value for normal and healthy weight. However, experts doubt that this classification is correct.

People who are a little rounder end up in the "overweight" group, even if they are generally not at risk to their health. Studies even suggest that being a few kilos over normal weight in old age prolongs life expectancy and also promotes good health.

This figure must be seen in the context of the ideal weight or ideal BMI defined by the WHO. Between 18.5 and 24.9 is called normal weight. Above this, one is classified as overweight and anyone with a BMI of 30 or more suffers from obesity or adiposity and requires treatment.

Not all fat is the same!

It is especially important where the fat is located on the body. The well-known lifebuoy on the belly is more likely to cause diabetes or a heart attack than fat deposits on the legs or arms.

Experts believe that the abdominal circumference is much more revealing than the number of kilograms. There is also "hidden fat" that you don't even see on a person, but which can still throw the metabolism out of balance. For this reason, one should never base the assessment on weight alone.