What is the BMI and how is it calculated?
Your body mass index evaluates your body weight in relation to your height. As the BMI is very easy to determine, it is still the most commonly used measure to assess whether normal weight, excess weight, or underweight is present.
The BMI is based on the ratio of body weight in kilograms and height in metres squared. The formula for calculation is as follows:
| BMI = | Weight [in kg] |
| Height2 [in m2] |
Example: A person is 1.75 m tall and weighs 88 kilograms. Therefore, the BMI yields a value of 28,73 kg/m2.
| BMI = | 88kg | = 28,73 kg/m2 |
| 1,75 m x 1,75 m |
Calculate your BMI now:
Enter your height and weight here.
BMI calculator
But what does this value tell us? The World Health Organisation (WHO) assumes the following categorisation for the assessment of the BMI:
| BMI [in kg/m2] | Category |
|---|---|
| < 18,50 | Underweight |
| 18,50 bis 24,99 | Normal weight |
| 25,00 bis 29,99 | Overweight |
| 30,00 bis 34,99 | Grade I obesity |
| 35,00 bis 39,99 | Grade II obesity |
| > 40,00 | Grade III obesity |
According to this classification, if the BMI is 25 kg/m2, you are overweight. Severe or pathological obesity – adiposis is the medical term – is present from a BMI of 30 kg/m2. Excess weight is associated with an increased risk of various complications. These include, for example, type 2 diabetes mellitus, cardiovascular diseases, gout, back pain, infertility and certain cancers.
Weighing correctly
How often? Once a week on the scales, always on the same weekday – preferably set a fixed weighing day from the outset.
When? The ideal time for the weight check is in the morning before breakfast.
What should you take care to do? Always use the same scales. Wear underwear or nothing on the scales. Always weigh yourself with an empty bladder and before you’ve had anything to eat or drink.
BMI – the “measure of things”?
The significance of the BMI has been questioned in recent years. For example, the value does not take body composition into account, that is, whether the weight of a person is primarily caused by fatty tissue or by muscle mass remains unclear. Under certain circumstances, overweight might therefore be calculated for well-trained body builders.
In addition, it does not provide information on where in the body the fat can be found. However, this is important regarding the health risk. Because as we know today, stomach fat is especially unhealthy. Fat cushions on the hips and bottom are comparatively harmless from a health perspective.
Therefore, the circumference of the abdomen should also be measured. You can obtain more detailed information about this and the WHtR here.
Good to know: The BMI has the advantage that it can be easily determined, and in a lot of people it can still be used to assess body weight – so it still works well as a warning signal.
