How Is BMI Calculated? Formula, Ranges and Standards

BMI (Body Mass Index) gives a rough estimate of body build from weight and height: BMI = weight (kg) ÷ height (m)².

For example, at 170 cm and 65 kg: convert height to 1.7 m, then BMI = 65 ÷ (1.7 × 1.7) ≈ 22.5, which falls in the normal range.

Common cut-offs for Chinese adults: BMI under 18.5 underweight, 18.5–23.9 normal, 24.0–27.9 overweight, 28 and above obese. The WHO places overweight at 25 and obesity at 30.

BMI cannot distinguish muscle from fat, so it is only a rough guide for athletes, pregnant people and similar groups — consult a doctor for health concerns.