BMI Calculator
Calculate your Body Mass Index (BMI)
Enter your height and weight to calculate BMI
How to Use
- Pick metric (cm / kg) or imperial (ft, in, lb)
- Enter your height and weight
- Read your BMI and the WHO category band
WHO adult bands: <18.5 underweight · 18.5–24.9 normal · 25–29.9 overweight · ≥30 obese.
When BMI Misses the Mark
BMI was built in the 1830s by Adolphe Quetelet for population-level statistics, not individual diagnosis. A 70 kg powerlifter with 12% body fat and a 70 kg sedentary person with 28% body fat get the same BMI — and that's exactly the point it's failing at. The American College of Sports Medicine has found BMI miscategorizes around 42% of athletes as overweight or obese when their body composition is actually healthy.
BMI also drifts at the edges. The WHO 2021 obesity briefing notes BMI under-estimates healthy weight for pregnant users and for adults over 65 by up to 2 kg/m². It also performs differently across ancestries — the WHO Asian-Pacific cut-off for "overweight" is 23, not 25. For children under 18, clinicians use pediatric BMI percentile charts (CDC growth charts) instead of the adult categories.
Treat this calculator as a screening first pass. If your BMI is borderline, the follow-up measurements worth asking a doctor about are waist-to-hip ratio, waist circumference relative to height (a ratio over 0.5 correlates better with metabolic risk than BMI does), and — if available — DEXA or bioelectrical impedance for actual body composition. This page is informational and not medical advice.