The Body Mass Index – often simply abbreviated as BMI – is a measure of a person’s body weight in relation to height. This index was invented as early as 1832 and has been continuously developed and reinterpreted ever since. When calculating the BMI, body weight is expressed in relation to height squared. The resulting unit of measurement of the Body Mass Index is given in kg / m².
With our online BMI calculator you can easily calculate your body mass index with all relevant parameters. We will also explain to you how to interpret the result.
The Body Mass Index Calculator
How is the BMI calculated?
To calculate the Body Mass Index, divide your weight by your height squared. The weight is given in kilograms and the height in meters. The result is your personal BMI:
In addition, parameters such as age and sex should also be considered, as well as the distribution of fat and muscle tissue in the body. The Body Mass Index offers you only a rough guideline which depends alot on your physical condition.
A rough overview of average BMI values by gender can be found in the following table. For exact values by gender and age you can use our online BMI calculator.
| Classification | Male | Female |
|---|---|---|
| Severe underweight | < 16.0 | < 15.0 |
| Moderate underweight | 16.0 -16.9 | 15.0 – 15.9 |
| Slight underweight | 17.0 – 18.4 | 16.0 – 17.4 |
| Normal weight | 18.5 – 24.9 | 17.5 – 23.9 |
| Overweight (preadiposity) | 25.0 – 29.9 | 24.0 – 28.9 |
| Obesity grade I | 30.0 – 34.9 | 29.0 – 33.9 |
| Obesity grade II | 35.0 – 39.9 | 34.0 – 38.9 |
| Obesity grade III | ≥ 40.0 | ≥ 39 |
Due to the physical difference between men and women, the Body Mass Index has to be assessed differently depending on the sex. On average, men have a higher proportion of muscle mass than women. This is why the BMI limits are slightly higher for men, both upwards and downwards.
As we age a part of the muscle mass disappears, but the fat is also distributed differently, so this variable must also be taken into account. With increasing age, a higher BMI value is considered normal weight, as this physical change is a natural process.
What is the BMI suitable for?
The Body Mass Index puts your weight in relation to your height, so you can roughly determine whether you are too heavy or too light for your body height. As many people find it difficult to assess themselves and the knowledge of their own body circumference can be very individual, the Body Mass Index can give you an approximate guide value for comparison and tracking. These indicators can also be used to warn about risk factors and illnesses, such as an unhealthy diet, lack of exercise or excessive alcohol consumption.
Pros and Cons of the Body Mass Index
The BMI tells us nothing about the composition and distribution of the body weight and neglects the fact that muscles are heavier than fat. So a very well-trained person with a lot of muscle mass would be classified as overweight, even though they are fully trained. This is why the value should only be considered as a rough guide value.
Nevertheless, there is a correlation between the body weight and the avereage life span. However, you should pay more attention to how much fat you have and where it is located on your body. Furthermore, the body mass index does not include parameters such as a person’s exercise habits and general fitness level, which have a huge influence on the likelihood of falling ill. The places where the fat is located also have a significant influence on health. This can also be the case if the BMI does not indicate overweight. If the fat is more likely to be deposited in the middle of the body, it significantly increases the risk of a heart attack or diabetes.
Alternatives to the BMI
If you want to classify the Body Mass Index even better and more precisely, you can also use other key figures. One variant is the “Waist-to-Height-Ratio“. The waist circumference is divided by the body size. It is about the distribution of abdominal fat, which can give a relatively accurate value about the health risks.
Another alternative is the Body Shape Index. This combines the previous value with the Body Mass Index and represents your physique as a formula. This gives you a relatively exact value regarding your physical condition.
So the Body Mass Index is becoming more and more accurate with the addition of various parameters, but it is best to combine it with other formulas in order to obtain a value about one’s own body that is as accurate and meaningful as possible. Except for people who do intensive fitness training, this can provide a rough guide to help you better assess yourself and your body. To know exactly, you can have a measurement of your fat and muscle mass done by a professional to get exact values about your body structure in detail.
A body fat scale is also a good way to get a better insight into your physical condition. Often these scales provide exact and detailed values which can even be tracked with a smartphone app.
BMI and bodybuilding
Anyone who trains regularly builds up muscles and muscles are known to be heavier than fat. As this parameter is completely ignored when calculating the Body Mass Index, the BMI is not suitable for people with high muscle mass to make a statement about the general body conditions. The body shape does not necessarily provide information here either, as leg and abdominal training also increases the size of body areas due to muscle growth. These formulas then tend to confuse your muscle mass with fat deposits. Especially as a bodybuilder you should rather fall back on a professional body measurement to be able to make an exact statement about your current physical condition.
Other calculators & tools
Fitness trackers can help you determine, track and analyse your personal fitness values. Here are some of the best and most common fitness trackers:
To get even more exact values about your body, you can also use our other calculators:
- Body Shape Index Calculator
- Calorie Calculator
- Waist-to-Height-Ratio Calculator
- Basal Metabolic Rate Calculator
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