BMI Calculator

You can easily calculate your own BMI using this BMI calculator. Simply enter your height and weight into the calculator. When you click “Calculate”, the BMI calculator will display a value: Your Body Mass Index.

BMI Calculator


BMI Table

Classification BMI
Underweight < 18,5
Normal weight 18,5 – 24,9
Overweight 25 – 29,9
Obese class I 30 – 34,9
Obese class II 35 – 39,9
Obese class III > 40

BMI – Body Mass Index

The acronym BMI stands for Body Mass Index. This index is a value which measures a person’s bodyweight relative to their height. In fact, it is defined as body mass divided by your height squared. Body Mass Index has the unit of measure kg/m². Body mass in kilograms and height in metres is used to calculate BMI. BMI is also known as the Quetelet Kaup Index. This name refers to the developer of the Body Mass Index but is rarely used.

Two athletes who make use of the bmi calculator during workout.

BMI Classification

If you look at BMI as just a simple number, it is not particularly significant. However, these numbers are attributed to specific classes with which you can interpret your BMI. These classes can be seen in the table above. The individual weight classes are explained briefly in the following:


If the BMI calculator reveals a value under 18.5 kg/m2, this is classified as “Underweight”. In this case, you should try to bring yourself up to a healthy normal weight in a healthy way – this means by eating a balanced diet in combination with exercise.

Normal weight:

If your Body Mass Index is in the range between 18.5 and 24.9 kg/m2, this is a normal weight. Those who want to achieve an optimal BMI should aim towards this range. This range indicates that the ratio of bodyweight to height is classed as healthy.


The BMI calculator also shows if someone has a problem because of their weight. If your BMI value is over 25 kg/m2, this is classed as “Overweight”. This classification applies up to a BMI of 29.9 kg/m2 and should be considered a warning sign for obesity.


As soon as your BMI reaches 30 or above, you are classed as “Obese”. Obesity is also known as adiposity or obeseness. The official classification according to the World Health Organisation, the WHO, describes further subdivisions of obesity – depending on the severity of your BMI. It is subdivided from Class I to Class III.

Optimally, your BMI should be in the “Normal weight” class, so between 18.5 and 24.9.

History of the BMI

The basis of today’s BMI – namely the formula used to calculate the body mass ratio – was developed in 1832 by the Belgian mathematician Adolphe Quetelet. In the first half of the 20th century, the Austrian researcher Ignaz Kaup further developed the index. He linked it to the topic of health.

BMI became the name of the formula for the first time in 1972 through the publication of an article by the American dietician, Ancel Benjamin Keys. However, Keys had not intended the BMI to be used to assess the body weight of individual persons. Rather, he applied the Body Mass Index for the statistical comparison of whole populations. In the 1980s, the World Health Organisation, or the WHO, used the name BMI and this is still used today.

BMI formula

Calculation of the BMI

As already mentioned above, the BMI and, therefore, also the BMI calculator evaluates bodyweight in relation to height. However, these two factors are not just simply compared – instead, height is calculated in square metres.
The formula to calculate BMI is as follows.

BMI = Body weight / (Body height * Body height)

Bodyweight is indicated in kilograms and height is given in metres. The best way to describe the calculation is to use an example. If you want to calculate the BMI of a man who is 1.92 m tall and 82kg, the formula is as follows:

BMI = 82 / (1,92 * 1,92) = 22,24

BMI is normally considered exclusively as a number. To be accurate, however, the units must be included. Therefore, in the example above, the man’s BMI is 22.24 kg/m2. It is far easier to use the BMI calculator on this website to determine Body Mass Index.

There are some details to note when calculating Body Mass Index with regard to gender and age:

  • Calculation of women’s BMI
  • Calculation of men’s BMI
  • BMI calculation for children and young people

How significant is BMI?

BMI is fixed in many people’s minds and is widely used accordingly. However, according to the increasing criticism of the use of the Body Mass Index, it should not be taken to heart. The focus of criticism is that there are factors which have an influence on bodyweight but not on the health of a person, yet are included in the calculation of BMI.

A high Body Mass Index is not necessarily due to being overweight. A high proportion of muscle mass, wide shoulders or even high bone density can mean greater bodyweight and, therefore, also a higher BMI. People who train regularly may weigh in heavier on the scales due to greater amounts of muscle mass although they may have a lower proportion of body fat and a good level of fitness. Endurance athletes, such as marathon runners, often have a BMI which would be classed as underweight although their bodies are in top physical condition and they are not malnourished.

When BMI is too high

If the BMI calculator reveals a high value, the reasons for this should be investigated nonetheless. First of all, you should rule out that the high BMI is due to greater muscle mass and would therefore be skewed. Those who are very physically active and muscular are not often overweight with a risk to their health. Therefore, they should not take BMI to heart.

For those with only little muscle mass or those who are not physically active, a higher Body Mass Index should be used as a warning sign for health problems. A high BMI for someone who does not take part in resistance training normally means they are overweight. Even if the reliability of Body Mass Index is not always a given, you should get more active before you reach a BMI over 30. A programme for targeted weight reduction through exercise and changing your diet should be followed in order to reduce the health risks associated with being overweight. If your BMI is extremely high, you should seek medical help.

When the BMI calculator reveals a low value

In most cases, the BMI calculator is used to determine whether a person is overweight. However, being underweight also presents a risk to your health and the Body Mass Index is also used in this respect. A BMI which is too low should also serve as a warning sign. In general, the further the value deviates from normal weight, the more urgent the need for treatment is.

A Body Mass Index below 17.5 is referred to by health professionals as a so-called ‘anorexic weight’. This threshold is often used to diagnose anorexia nervosa. If your BMI is below this level, you should seek medical advice and treatment.