BMI Calculator
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About BMI Calculator
Calculate Body Mass Index (BMI) from height and weight. Metric (kg/cm) or US (lb/in) units. Shows the WHO category (underweight / normal / overweight / obese).
BMI = weight (kg) ÷ height² (m²). It's a screening tool, not a diagnosis. The category boundaries (18.5 / 25 / 30) are population-level statistics that don't account for muscle mass, body composition, ethnicity, or age — a body-builder with 10% body fat can be BMI-overweight, an elderly person at 'normal' BMI can be at risk of sarcopenia.
For more nuanced body-composition assessment, look at waist-to-hip ratio, body fat percentage, or DXA scan. BMI is useful as a rough screen and a population-level metric; clinically it's one input alongside others.
Common questions
What's a healthy BMI?
WHO defines 18.5-24.9 as 'normal weight' for adults. Children and teens use age-and-sex-adjusted percentile charts instead.
Why is BMI considered flawed?
It treats muscle and fat the same. A muscular athlete and a sedentary person can have identical BMI but very different health profiles.
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