Body mass index is a quick screening ratio between weight and height — useful for spotting trends, not a diagnosis. Enter metric or imperial values; the classification follows the WHO adult ranges.
Formula & methodology
Metric: BMI = kg ÷ m². Imperial: BMI = 703 × lb ÷ in². WHO adult ranges: underweight < 18.5 · normal 18.5–24.9 · overweight 25–29.9 · obesity ≥ 30.
Worked example
70 kg at 175 cm → 70 ÷ 1.75² = 22.86 → normal range. The same person in imperial units (154.32 lb, 5′8.9″) gets the same result — the units cancel out.
Limits — read this
BMI cannot tell muscle from fat: athletes often score "overweight" while carrying little fat, and the ranges are adult-only — they do not apply to children, pregnancy, or frail elderly people. Use it as a rough screen, and talk to a professional about anything that matters.