What is the Body Mass Index?

Physicians often use the Body Mass Index to determine a person’s weight risks. The BMI compares weight to height. When a person’s BMI is greater than 30, that person is considered obese. When a person’s BMI exceeds 40, that person is considered morbidly obese.

Calculate your Body Mass Index (BMI)

BMI Classification

< 18.5 = underweight
18.5-24.9 = normal weight
25.0-29.9 = overweight
30.0-34.9 = class I obesity
35.0-39.9 = class II obesity
≥ 40.0 = class III obesity

You can also visit the Centers for Disease Control to learn more about obesity.


Centers for Disease Control and Prevention: Obesity and Overweight Topics

Obesity definitions

Center for Disease Control and Prevention: Defining Overweight and Obesity

Table of weight, height and BMI

National Heart Lung and Blood Institute: Obesity Guidelines