What BMI is
BMI = weight (kg) ÷ height (m)². It expresses weight relative to height as a single number. For example, 70 kg at 175 cm is 70 ÷ 1.75² ≈ 22.9.
Standards differ: WHO vs Asia-Pacific
People of Asian descent face higher metabolic risk at the same BMI, so Korean guidelines use lower cut-offs than the WHO.
| Category | Korean (BMI) | WHO (BMI) |
|---|---|---|
| Underweight | below 18.5 | below 18.5 |
| Normal | 18.5–22.9 | 18.5–24.9 |
| Overweight | 23–24.9 | 25–29.9 |
| Obese | 25 and above | 30 and above |
This tool applies the WHO standard on the English site (and the Korean Society for the Study of Obesity standard on the Korean site), and also shows the healthy weight range for your height.
What BMI misses
BMI uses only height and weight, so it has limits.
- Can't tell muscle from fat: athletes can read high without being obese.
- Ignores fat distribution: at the same BMI, belly fat is riskier — check waist circumference too.
- Elderly, children, pregnancy: different standards apply.
Treat BMI as a rough guide and consult a professional for an actual assessment. Your height and weight are never uploaded — everything is computed in your browser. For other unit conversions, see the Unit Converter.