What is BMI?
BMI is calculated by dividing weight in kilograms by the square of height in meters: BMI = Weight (kg) / Height² (m²). It's a simple, internationally recognized screening tool.
WHO Classification Table
| BMI | Classification |
|---|---|
| < 16 | Severe underweight |
| 16 – 18.5 | Underweight |
| 18.5 – 25 | Normal weight |
| 25 – 30 | Overweight |
| 30 – 35 | Obesity class I |
| 35 – 40 | Obesity class II |
| > 40 | Morbid obesity |
BMI Limitations
BMI does not distinguish fat from muscle mass. It may overestimate body fat in muscular athletes and underestimate it in older adults. Not applicable to children, pregnant women, or those over 65 without adaptation.
Frequently Asked Questions
How to calculate BMI?
Divide your weight (kg) by the square of your height (m). E.g.: 70 kg / (1.75 m)² = 22.9.
What is a healthy BMI?
A BMI between 18.5 and 24.9 is considered normal by WHO. The ideal varies by age and sex.
Is BMI reliable for athletes?
No. Muscular athletes may have high BMI without excess fat. Use waist circumference or bioimpedance instead.
At what BMI is someone obese?
Obesity starts at a BMI of 30 according to WHO classification.
Does BMI apply to children?
No. Use WHO growth charts for children and adolescents.