Calculators · General Medicine · Formula

Body mass index (BMI)

Also called Quetelet index, BMI calculator

Weight for height in adults, with WHO categories and the WHO public-health action points for Asian populations.

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Formula and scoring

BMI = weight (kg) ÷ height (m)². WHO: <18.5 underweight, 18.5–24.9 normal, 25–29.9 pre-obese, 30–34.9 / 35–39.9 / ≥40 obese class I / II / III.

Exam and ward pearls

  • BMI does not separate fat from muscle and misses central obesity; add waist circumference or waist-to-height ratio.

When not to rely on it

  • Not for children and adolescents (use age- and sex-specific BMI centiles) or pregnancy.

Source

  1. WHO Expert Consultation. Appropriate body-mass index for Asian populations and its implications for policy and intervention strategies. Lancet. 2004;363(9403):157-63. doi:10.1016/S0140-6736(03)15268-3 · PMID 14726171
  2. World Health Organization. Obesity: preventing and managing the global epidemic. WHO Technical Report Series 894. Geneva: WHO; 2000. Link

Formula and cut-offs checked against these sources on 8 Nov 2026. Educational tool for clinicians; it does not replace clinical judgement.

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