Body mass index (BMI)
An adult's BMI from weight and height, and the weight range that corresponds to a normal BMI at that height.
Tool
Tools › Health
How it is calculated
BMI = weight (kg) ÷ height (m)². Weight for a given BMI = BMI × height (m)².
Worked example: 70 kg and 175 cm. Height² = 1.75 × 1.75 = 3.0625 m²; BMI = 70 ÷ 3.0625 = 22.9 kg/m². Normal range: 18.5 × 3.0625 = 56.7 kg to 24.9 × 3.0625 = 76.3 kg.
Keep in mind
- Support calculation: BMI is a screening tool, not a diagnosis. Check with a professional.
- WHO classification in adults (kg/m²): severe thinness < 16; moderate 16-16.9; mild 17-18.4; normal 18.5-24.9; overweight 25-29.9; obesity class I 30-34.9, class II 35-39.9 and class III ≥ 40.
- Not valid in children and adolescents (percentile charts by age and sex are used), in pregnancy, in very muscular people, with oedema or amputations, or in elderly people who have lost height.
- In some Asian populations risk rises at lower BMI values. In malnutrition, especially in children, mid-upper arm circumference is more useful.