What is body mass index (BMI)?
Body mass index (BMI) is a number calculated from a person's weight and height. BMI helps assess whether a person's weight is normal, too low, or too high. It is the most widely used weight assessment method in the world.
How to calculate BMI?
BMI = weight (kg) / height (m)²
For example, if you weigh 70 kg and your height is 175 cm (1.75 m), your BMI = 70 / (1.75 × 1.75) = 22.9. This means your weight is normal according to WHO categories.
BMI categories according to WHO
The World Health Organization (WHO) defines the following BMI categories for adults:
- Underweight: BMI less than 18.5
- Normal weight: BMI from 18.5 to 24.9
- Overweight: BMI from 25 to 29.9
- Obese: BMI 30 and above
BMI calculation examples
Woman: weight 60 kg, height 165 cm. BMI = 60 / (1.65 × 1.65) = 22.0 — normal weight.
Man: weight 95 kg, height 180 cm. BMI = 95 / (1.80 × 1.80) = 29.3 — overweight.
Teenager: BMI for children and teenagers is evaluated differently — age- and gender-specific percentile charts are used.
What is a normal BMI?
A normal BMI for adults ranges from 18.5 to 24.9. This range is associated with the lowest risk of chronic diseases. However, the optimal BMI may vary depending on age, gender, muscle mass and ethnic background.
What are the limitations of BMI?
BMI is an indicative measure and does not account for muscle mass, age or gender. For athletes and very active people, BMI may show a higher value due to muscle mass. BMI is also not suitable for pregnant women and elderly people. Always consult a doctor for an individual health assessment.