What is the name of the measure of body fat calculated from a person's weight and height?

The measure of body fat calculated from a person’s weight and height is body mass index, or BMI. It is calculated by dividing mass in kilograms by height in metres squared; pounds-and-inches calculations use a conversion factor of 703.

BMI became widely known through the work of Belgian mathematician and statistician Adolphe Quetelet, who developed the underlying ratio between 1830 and 1850. He called it the Quetelet Index and did not originally design it as an individual medical test. The term “body mass index” was introduced in 1972 by physiologist Ancel Keys and colleagues.

For adults, commonly used categories describe BMI below 18.5 as underweight, 18.5–24.9 as within the usual healthy range, 25–29.9 as overweight, and 30 or higher as obese. These are population-level screening categories, not diagnoses.

A common mix-up is treating BMI as a direct body-fat measurement. It does not distinguish fat from muscle, bone, or fluid, so a muscular athlete may have a high BMI without having excess body fat. Waist circumference and other clinical measures can provide additional context.