BMI: what it is, how to calculate and results table

BMI is the acronym for Body Mass Index, which is a calculation used to assess whether a person is within their ideal weight in relation to height. Thus, according to the value of the BMI result, the person can know if he is within the ideal weight, above or below the desired weight.

Being within the right weight is important because being over or under that weight can greatly influence health, increasing the risk of diseases such as malnutrition when you are underweight, and stroke or heart attack, when you are overweight. Thus, it is common for doctors, nurses and nutritionists to assess the person's BMI in routine consultations to check for the possibility of diseases that the person may be pre-disposed to.

How to calculate BMI

The BMI calculation must be done using the following mathematical formula: Weight รท (height x height). But you can also find out if you are within the ideal weight using our online calculator, just by entering your data:


This formula is ideal for calculating the weight of healthy adults. In addition, the waist-hip ratio calculation can also be used to assess the risk of having cardiovascular diseases, such as diabetes and heart attack. See how to calculate here.

BMI Results Table

Each BMI result must be evaluated by a health professional. However, the following table indicates the possible BMI results, according to the World Health Organization, with a BMI between 18.5 and 24.9 representing the ideal weight and the lowest risk for some diseases.

ClassificationBMIWhat can happen
Very underweight16 to 16.9 kg / m2Hair loss, infertility, menstrual absence
Under weight17 to 18.4 kg / m2Fatigue, stress, anxiety
Normal weight18.5 to 24.9 kg / m2Lower risk of heart and vascular disease
Overweight25 to 29.9 kg / m2Fatigue, poor circulation, varicose veins
Obesity Grade I30 to 34.9 kg / m2Diabetes, angina, heart attack, atherosclerosis
Grade II Obesity35 to 40 kg / m2Sleep apnea, shortness of breath
Grade III Obesitygreater than 40 kg / m2Reflux, difficulty in moving, bedsores, diabetes, heart attack, stroke

Whoever is not within the ideal weight should adapt their diet and exercise to achieve the most suitable weight for their height and age.

When you are under ideal weight, you should increase your consumption of nutrient-rich foods so that your body has what it takes to protect itself from disease. Those who are overweight should consume fewer calories and do some physical activity to eliminate fat stores, which increases the risk of heart disease.

When not to calculate BMI

Although the BMI is widely used to check whether the individual is overweight or not, this method has some flaws and, therefore, it is recommended that in addition to it, use other means of diagnosis to check whether the individual is really above or below ideal weight, such as measuring the fat crease, for example.

Thus, BMI is not the ideal parameter to assess the ideal weight in:

  • Athletes and very muscular people: because it does not take into account the weight of the muscles. In this case, neck measurement is a better option.
  • Elderly: because it does not take into account the natural reduction of muscles at these ages;
  • During pregnancy: because it does not take the baby's growth into account.

In addition, it is contraindicated in cases of malnutrition, ascites, edema and in bedridden patients.

A nutritionist will be able to personally do all the calculations necessary to assess your weight and how much you need to put on or lose weight, taking into account your general health.

Why it is important to be within the ideal weight

It is important to be within the ideal weight because the right weight is closely linked to the person's state of health.

Having a small accumulation of fat in the body is important so that there are reserves of energy so that when the person gets sick, they have time to recover. However, excess fat accumulates in the liver, waist and also within the arteries making it difficult for blood to pass, and this increases the risk of heart disease.

Therefore, being within the ideal weight is important for increasing health, preventing cardiovascular disease and increasing quality of life. Thus, those who are underweight must increase muscle volume to increase weight in a healthy way and those who are overweight must burn fat to gain health.

Find out if your child is at the ideal weight and how to get him to this weight by clicking here.