How do BMI calculators for women work?

Body Mass Index calculators work by multiplying the patient's weight in pounds by 703, then dividing that figure by the square of the patient's height in inches. BMI is a measure of the patient's overall body fat.

BMI calculators use the same formula for both men and women. Additionally, the BMI range that constitutes a healthy weight is the same for both genders.

Some BMI calculators take factors such as age and sex into account to determine the percentile that a person falls into. A person's weight percentile determines how close they are to the national average. In the United States, a person with a healthy weight is defined as having a BMI of between 18.5 and 24.9 as of 2015. This means that a five-foot, nine-inch tall woman should weigh between 125 and 168 pounds. A shorter woman should weigh proportionally less.

While BMI may be a useful tool in some instances, it is not an accurate measure of a person's overall health because it does not take body composition into account. For example, lean muscle weighs more than fat, therefore a very muscular person may have a BMI that erroneously indicates that they are overweight. An elite athlete may have a higher BMI than an inactive person, yet the inactive person may be more overweight and unhealthy than the athlete.