How To Calculate Your BMI

The body mass index (BMI) is an indicator used to determine whether a person is their ideal weight or not; it is calculated from a few variables.
How To Calculate Your BMI

Last update: 10 October, 2018

The body mass index is one of the most effective indicators to determine if a person is at their ideal weight, or not. The formula to determine the body mass index (BMI) is very simple. However, many people do not know how to make this calculation in an effective way.

What is the body mass index and what is it for?

The World Health Organization, (WHO), adopted this index. Its purpose is to determine the risk levels related to weight and obesity. It also helps to determine if a person is below the recommended weight.

The body mass index is a formula, created by the Belgian mathematician, Adolphe Quetelet. Sometimes known as the Quetelet Index, fundamental factors such as, age and sex will determine the BMI.

Importance of BMI. Woman losing weight.

The BMI is a very simple but effective formula to establish the average weight of a person. It’s important to remember that a healthy weight depends on height, physical activity, and age. This is the key to maintaining good health.

The importance of BMI and its relationship with health, is recognized by professionals. The formula is commonly used around the world, by physicians and nutritionists.

The BMI is an important indicator of health. Several studies have found a connection between a very high BMI, and premature death. That is, the higher the body mass index, the greater the chances that the person will die prematurely, or the life expectancy will be shorter than the average.

Woman measuring belly for BMI calculation.

How to calculate the body mass index?

As we have seen previously, the body mass index is a very simple formula. In the calculation of the formula, it’s necessary to relate weight and height. For this, it’s essential to determine the correct circumference of the abdominal area.

The BMI can be calculated from the age of two years. It’s one of the formulas most utilized by specialists around the world. However, if  the person has a large muscle mass, the result may falsely indicate a larger amount of fat.

This is, in fact, one of the main defects of the formula- the volume of the person and its relationship with accumulated fat. Therefore, it’s always advisable to go to a specialist.

However, certain factors go beyond the formula’s calculation and should be taken into consideration. The two main considerations are: weight of muscle mass and water retention. It’s also important to note that this formula isn’t valid for pregnant women.

The BMI is not valid for pregnant women.

Data to calculate BMI

To calculate BMI, we must divide body weight in pounds, between the square of the height in inches. By using a chart as a comparison, the data will indicate if the BMI is below, above, or at the correct average.

It’s important to note, that the chart only applies to adults over 18 years of age. Therefore, in the case of children, the formula must be completed by a specialist.

If the BMI is less than 18.5, the person in question is too thin. On the contrary, the person is overweight if the result is higher than 25.

When the BMI exceeds 30, the person may be obese. If the body mass index is between 18.5 and 24.9, the person is at their ideal weight, according to size, age, and sex.


This text is provided for informational purposes only and does not replace consultation with a professional. If in doubt, consult your specialist.