Why is the body mass index (BMI) calculated?

The body mass index (BMI) is primarily calculated to categorize individuals into different weight classifications such as underweight, normal weight, overweight, or obesity. This classification helps in assessing an individual’s health risks associated with different weight categories. BMI uses a person's height and weight to create a numerical value, and higher or lower values can indicate whether a person is at risk for various health conditions linked to their weight.

While BMI is a useful screening tool for identifying potential weight-related health issues, it does not directly measure body fat percentage or muscle mass, nor does it evaluate metabolic rate. These other aspects of body composition and health require more precise methods beyond the simple height-to-weight ratio that BMI provides. Hence, the primary purpose of calculating BMI is its ability to categorize weight status for public health and clinical assessments.