What does "BMI" stand for?

BMI stands for Body Mass Index, a number calculated from a person’s body mass and height. It is found by dividing weight in kilograms by height in metres squared.

The index is commonly used as a broad screening tool for weight categories in adults. A BMI below 18.5 is often classified as underweight, 18.5 to 24.9 as normal weight, 25 to 29.9 as overweight, and 30 or higher as obese. These ranges describe statistical categories rather than a complete diagnosis of an individual’s health.

The idea originated with Belgian mathematician and statistician Adolphe Quetelet, who developed the Quetelet Index in the 19th century. The term “body mass index” became widely established after a 1972 paper by physiologist Ancel Keys and colleagues.

BMI has important limitations. It does not distinguish muscle from fat, so muscular athletes may receive a high value. It also does not show where fat is distributed or account fully for age, sex, ethnicity, or health conditions. Doctors therefore consider BMI alongside other measurements and medical information.