Which formula correctly calculates body mass index (BMI)?

• A. BMI = weight (lb) / height (in)^2
• B. BMI = height (m) / weight (kg)^2
• C. BMI = weight (kg) / height (m)^2
• D. BMI = heart rate × age

Answer: (C)

BMI measures body mass relative to height using a weight divided by height squared relationship. In metric units, that means weight in kilograms divided by height in meters squared. This form yields a unitless number used to categorize weight status, and it matches the standard definition precisely. If you use pounds and inches, you’d need to adjust with a factor (703) to keep the calculation equivalent, not simply weight divided by height squared. The other formulas either place the variables in the wrong order or rely on unrelated measurements like heart rate and age, so they don’t define BMI.