How it works
BMI is weight divided by height squared:
BMI = weight (kg) / [ height (m) ]2
Using imperial units:
BMI = 703 × weight (lb) / [ height (in) ]2
The standard adult categories are: under 18.5 = underweight, 18.5–24.9 = normal, 25–29.9 = overweight, 30+ = obese.
Worked example
Someone 1.75 m tall weighing 70 kg:
- height² = 1.75 × 1.75 = 3.0625
- BMI = 70 / 3.0625 ≈ 22.9 → normal weight