How is BMI calculated, and what are the conventional categories?

• A. BMI = weight (lb) / height (in)^2.
• B. BMI = weight (kg) / height (m)^2; underweight <18.5; normal 18.5–24.9; overweight 25–29.9; obesity ≥30.
• C. BMI = height in meters divided by weight in kilograms.
• D. BMI categories are under 18, 18–24, 24–29, 30+

Answer: (B)

BMI estimates body fat by comparing weight to height, using the metric formula: weight in kilograms divided by height in meters squared. When expressed this way, the conventional categories are: underweight less than 18.5; normal weight 18.5 to 24.9; overweight 25 to 29.9; obesity 30 or greater.

The other formats aren’t the standard calculation. Using pounds and inches would require multiplying by 703 to match the metric formula, otherwise the numbers don’t align with the established ranges. Reversing the formula (height divided by weight) doesn’t reflect how BMI relates weight to height. And using broad, imprecise ranges like under 18, 18–24, 24–29, 30+ misses the decimal cutoffs (18.5, 24.9, 29.9) that define the conventional categories.