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Body Mass Index (BMI)

BMI is weight in kilograms divided by height in metres squared. It classifies adults as underweight (<18.5), normal (18.5–24.9), overweight (25–29.9) or obese (≥30, classes I–III).

Weight (kg or lb)
Height (cm or m or in)

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Interpretation

Result	Meaning
< 18.5	Underweight
18.5–24.9	Normal
25–29.9	Overweight
30–34.9	Obesity class I
35–39.9	Obesity class II
≥ 40	Obesity class III

Formula

BMI = weight (kg) ÷ height (m)²

Clinical pearls

Asian populations: WHO suggests action points of 23 (increased risk) and 27.5 (high risk).
BMI does not distinguish fat from lean mass; interpret with waist circumference in muscular or older patients.

Examples

bmi for 82 kg and 178 cm what is the BMI of someone 5'6" and 150 lbs body mass index 95kg 1.80 m

FAQ

What is a normal BMI?

For adults, 18.5 to 24.9 kg/m² is classified as normal weight by the WHO.

Is BMI valid for children?

No. Children use age- and sex-specific BMI percentiles rather than the adult cut-offs.

Evidence

WHO. Obesity: preventing and managing the global epidemic. Technical Report Series 894 (2000).

General & Anthropometrics · Reviewed 2026-10-14 · Methodology