9.3.2 Math in Health Care
The calculator can be accessed on the left-hand side bar under Toolkit.
The body mass index (BMI) is sometimes used to help determine whether an adult is under- or overweight. It is calculated as follows:
Although care needs to be taken in interpreting the results (for example, the formula isn’t appropriate for children, old people, or those with a very muscular physique), a BMI of less than 20 suggests the person is underweight, and a BMI of over 25 suggests the person is overweight.
In this formula, the units have been included in the expression on the right side of the equals sign. It is important to change any measurements into these units before you substitute the values into the formula. (No units have been included for the BMI on the left side, in line with current health care practice.)
Activity: Body Mass Index
If an adult man is 5 feet, 10 inches tall and weighs 185 pounds, calculate his BMI and decide whether he is overweight.
The formula needs the weight in pounds and the height in inches. First, convert the height into inches. Since there are 12 inches in a foot: .
Substituting the weight and height into the formula for the BMI gives:
Since his body mass index is over 25, the man is probably overweight. [ What would be a healthy weight for him? Use a BMI of 25 and his height and see if you can work backwards - you should come out with about 174 pounds. ]