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Vital Things You Should Know About BMI

Achieving and maintaining healthy body weight is crucial in healthy living, and it is the secret to preventing the effects of being underweight or overweight.

But how do you determine your healthy weight?

This is where the Body Mass Index comes in. Popularly known as BMI, this is the perfect way of determining your ideal healthy weight. The technique compares the individual’s mass against height to get the desired weight.

What is BMI?

The Body Mass Index refers to the measurement (comparison) of an individual's weight to height. Therefore, it is more of an indicator than a direct measurement of one's total body fat. It often correlates with the total body fat, which explains why the latter increases with an increase in BMI score. Thus, BMI is an effective technique to determine whether one is underweight, overweight, or within the healthy range.

All units (weight and height) must be expressed in their SI units (kilograms and meters, respectively) when determining the BMI score. An individual's BMI score is calculated by dividing their weight by the square of their height, and a high BMI score translates to increased body fat.

It is ideal for screening the dangerous weight categories that are likely to result in health issues (both underweight and overweight). The method does not, however, diagnose an individual's body fat or health.

 WHO classifies any adult with a BMI score between 25 and 29.9 as overweight. Those with 30 or more are obese, while anything below 18.5 is underweight. Based on the categories, the healthy weight for adults ranges between 18.5 and 24.9. 

How to Check BMI In Both Adults and Children

Checking BMI is the same for both children and adults. As mentioned above, it is determined by comparing the individual’s mass (in kgs) against the square of their height (centimeters).

Both measurements should be expressed in the SI units (kgs and centimeters) at all times. The only difference is, however, that the normal BMI range is the same for all adults.

However, it is different for children as they constantly grow, thus changing their height and weight tremendously. Therefore, checking BMI in children measures their weight and size compared to that of the rest of the same age.

The BMI percentile is a common term at the pediatrics clinics and other experts who deal with children's health. It refers to the comparison of a child's weight and height versus that of age.

BMI Charts and Formulas

As mentioned above, BMI is among the most reliable ways of determining body fatness. The goal is to screen and identify all weight categories that are likely to result in health complications.

It is an easily computable measurement that applies to both men and women. All you need is your height and weight in their standard or metric measures, and you are good to go.

The BMI tables are useful tools at this point. These tables show a comparison of height and weight (pounds), which in the end help you to determine if you are underweight, overweight, or carry a healthy weight. View the BMI tables applicable for adults at age 20 and above.

Besides the BMI tables or charts, the following tool should also help determine the BMI score among adults. You should enter your height and weight in either their standard or metric measures. By selecting compute, your BMI score should appear below.


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WHO classifies people into four categories based on their BMI score. Those with a BMI score less than 18.5 are underweight as the healthy weight falls between 18.5 and 24.9. Anything above 25.0 to 29.9 is overweight. There are also obese people whose BMI score is 30.0 or above.

Body weight recommended by WHO based on BMI( For men & women over 18 years of age)



BMI range - kg/m2

Severe Thinness

< 16

Moderate Thinness

16 - 17

Mild Thinness

17 - 18.5


18.5 - 25



25 - 30

Obese Class I

30 - 35

Obese Class II

35 - 40

Obese Class III

> 40


The imperial formula of finding an individual's BMI score involves using pounds and inches for weight and height, respectively. Metric, on the other hand, entails kilograms and centimeters.

Whatever option you choose, you should arrive at the same score.

The rapid growth among children makes it unsuitable to use the above technique in determining their ideal BMI score. The process begins with the standard BMI calculation as done in adults before comparing it against their age.

The value is them further compared against that of their age-mates to determine the BMI percentile. The percentile value determines whether the child is underweight, overweight, obese, or average.

BMI Table for children and teens( Age 2-20 years)

BMI categorization for children by the Centers for Disease Control and Prevention (CDC) 



Percentile Range



Healthy weight

5% - 85%

At risk of overweight

85% - 95%




Interpreting the Results (Children and Adults)

As mentioned above, all adults whose BMI score is below 18.5 are classified as underweight and should increase their weight.

The average weight falls between the BMI score of 18.5 and 24.9. Anything from 25.0 to 29.9 is overweight, and individuals should achieve and maintain a healthy weight.

Obese people are at the risk of suffering weight-related issues, and their BMI score ranges from 30.0 and above. 

The metric formula for calculating in children is 

weight/height squared * 10000

Standard formula

Weight/height squared* 730

The BMI percentiles for children help determine whether the child is normal, underweight, overweight, or obese.

Children lower than the 5th percentile are underweight, and the average weight falls between the 5th and 85th percentile. Those above 85th and below 95th percentiles are overweight while the rest are obese (95th and more).

Limitations of BMI

Despite being a reliable way of determining body fat mass and its effects on human health, BMI also carries some limitations, as outlined below.

The BMI is merely a rational comparison between height and weight, and it doesn't account for body composition.

In the end, it does not account for whether the individual’s weight is predominantly muscles or fat. In such cases, most physically fit and muscular people may easily be overweight with this assessment.

As for the average person, the body composition is a relatively accurate estimate of whether or not they fall into the ideal weight range.

Why Use BMI For Fitness Goals

Your BMI measurement compares your weight and height, and it helps determine whether you are obese, underweight, regular, or overweight. In cases where you find yourself in the obese or overweight categories, you can also use it to work towards your desired fitness goals.

In the end, you don't just enjoy your fitness goals but also maintain a healthy weight that prevents weight-related issues.

Benefits of A Healthy Weight

The healthy weight, according to the BMI charts, falls between 18.5 and 24.9 scores in adults. In children, it ranges between the 5th and 85th percentile. Health experts recommend maintaining a healthy weight for the following reasons:

  • It promotes efficient blood circulation
  • Easier management of body fluids.
  • Lower risk of weight-related complications.

Health Risk of Extra Weight

Extra weight also brings with it a range of risks. These risks include sleep apnea, diabetes sleep apnea, osteoporosis, gall stones, certain cancers, diabetes, and breathing problems.

Achieving a healthy weight is the secret to preventing most lifestyle-related complications. Maintaining this weight is, however, the greatest challenge for most people.

It involves various techniques such as staying active, eating a healthy and balanced diet and adhering to daily calorie requirements. Incorporating more fruits and vegetables into your diet is also crucial.