BMI Calculator

It's a rough screening number, not a measure of health. BMI doesn't distinguish muscle from fat, doesn't account for where body fat is distributed (visceral vs subcutaneous, which matters a lot for risk), and doesn't capture metabolic markers. Use it as a starting point — actual health assessment needs more than this one number.

They aren't, strictly. The standard adult categories (18.5 / 25 / 30) come from large population studies. WHO has separately recommended different thresholds for some Asian populations (overweight at 23, obese at 27.5) because the same BMI maps to different health risk profiles. Pediatric and pregnant BMI use entirely different reference curves.

Generally no — strength athletes, bodybuilders, and many professional sports players carry enough muscle that BMI reports them as overweight or obese despite low body fat. Methods that estimate body fat directly (DEXA scans, hydrostatic weighing, bioelectrical impedance, or skin-fold measurement) are more useful for them.

WHO classifies 18.5–24.9 as 'normal weight'. But 'healthy' depends on many factors beyond BMI. Two people at the same BMI can have very different health risks based on body composition, fitness level, family history, and metabolic markers. The category alone doesn't tell you whether you're healthy.

No — children and adolescents need pediatric BMI percentiles (relative to their age and sex group), not the adult WHO categories. This calculator uses the adult thresholds; for kids, use a CDC or WHO pediatric percentile chart with a pediatrician.

No. The calculation runs entirely in your browser and nothing is transmitted. Your height, weight, and result never leave your device.

Class I (30–34.9), Class II (35–39.9), and Class III (≥40) reflect different magnitudes of elevated cardiovascular and metabolic risk in population studies. They're rough buckets used by clinicians and researchers, not different conditions.