CalRegional Medical Assistant Practice Exam

In the metric system, BMI is defined as weight in kilograms divided by the square of height in meters. This gives the index BMI = weight (kg) / [height (m)]^2, which simplifies to a unit of kg/m^2. Using kilograms and meters with the height squared normalizes body mass for a person’s stature in a way that correlates with body fat without needing extra conversion factors.

If you tried to use pounds and inches, you’d either get a different unit (lb/in^2) or you’d have to include a conversion constant (the 703 factor) to match the kg/m^2 scale. Swapping the numerator and denominator would also make no sense for BMI, as it would not reflect how weight relates to height.

So the correct metric form is weight in kilograms divided by the square of height in meters. For example, someone who is 70 kg and 1.75 m tall would have BMI ≈ 70 / (1.75^2) ≈ 22.9.