What is BMI and why does it matter?
BMI (Body Mass Index) is a widely used measure to assess whether a person’s weight is appropriate in relation to their height. It is a simple, practical tool recognized by the World Health Organization (WHO) for estimating the degree of thinness or obesity in an adult individual.
The BMI formula is as follows:
BMI = weight (kg) ÷ height² (m²)
In other words, body weight in kilograms is divided by height in meters squared. The numerical result allows a person to be classified into categories such as underweight, normal weight, overweight, or obese.
Why are age and sex relevant?
Although the BMI calculation is the same for everyone, interpreting the value varies depending on age and sex, especially in two groups: children/adolescents and the elderly.
In children and adolescents, the body is still developing. Therefore, BMI should be assessed based on growth charts specific to age range and biological sex.
In older adults, there is a natural tendency to lose muscle mass and redistribute fat. As a result, slightly higher BMI values may be considered normal, especially if there is no associated cardiovascular risk.
In addition, women tend to have more body fat than men, even with the same BMI. Men, on the other hand, generally have more muscle mass, which can also influence the interpretation of the index. Therefore, BMI is a starting point and does not replace a full clinical assessment.
What is BMI used for?
BMI is a useful tool for:
Identifying risks associated with malnutrition, overweight, or obesity
Helping health professionals in nutritional screening
Monitoring weight changes over time
Guiding recommendations for diet and physical activity
However, it does not assess body composition (how much is fat, muscle, or bone) nor the distribution of fat in the body, which are also important factors for health.
Calculate your BMI right now!
BMI Calculator
⚖️ Need help to convert your weight in pounds to kilograms to add to the calculator?
This calculator uses kilograms (kg), which is the international metric unit for weight. If you’re more familiar with pounds (lbs), use this quick converter below to input your weight correctly.
Pounds to Kilograms Converter
🌎 Need help converting feet to centimeters?
In the United States, height is commonly measured in feet and inches, while this calculator uses centimeters (cm), which is part of the international metric system. If you’re unsure how to convert, use the tool below. Simply enter the height in feet and inches, and it will show you the equivalent in centimeters.
Feet to Centimeters Converter
Conclusion
BMI is an important starting point for assessing a person’s nutritional health. When used alongside information such as age, sex, lifestyle habits, and medical history, it can help identify risks and support more informed decisions about health and well-being.
