Body mass index (BMI) is a measure of body fat based on height and weight. It is used to screen for weight-related health problems such as obesity, underweight, and eating disorders.
BMI is calculated by dividing weight in kilograms by the square of height in meters. A BMI of 18.5 to 24.9 is considered normal, a BMI of 25 to 29.9 is considered overweight, and a BMI of 30 or higher is considered obese.