BMI (Body Mass Index)
Body mass index calculation and WHO cardiometabolic risk categorization.
Switch how results are explained
Normal weight (18.5–24.9 kg/m²). Lowest overall cardiometabolic risk; maintain healthy diet and regular exercise.
- Evidence grade
- A
What it is and when to use it
Body Mass Index (BMI) is calculated as weight in kilograms divided by height in meters squared (kg/m²). It is the standard population screening tool endorsed by the World Health Organization (WHO).
How to interpret it
BMI <18.5 is underweight; 18.5–24.9 is normal weight; 25.0–29.9 is overweight; 30.0–34.9 is Class I obesity; 35.0–39.9 is Class II obesity; and ≥40.0 is Class III (severe) obesity.
Limitations and when not to use it
BMI does not directly measure body fat percentage and may misclassify muscular athletes, pregnant women, or sarcopenic elderly individuals.
Frequently asked questions
- Is BMI suitable for children?
- In children and adolescents under 18, BMI must be interpreted using age- and sex-specific percentile growth charts rather than fixed adult cut-offs.
Formulas and cut-offs are from the original authors of each score; see the references.
Last reviewed: June 2026
References
- Physical status: the use and interpretation of anthropometry. Report of a WHO Expert Committee. World Health Organ Tech Rep Ser. 1995;854:1-452. PMID:8594834