How to Calculate Whether You Are Underweight or Normal

Body Mass Index, or BMI, is a calculation based on weight and height used to determine an adult man or woman's body fat. According to the Centers for Disease Control and Prevention, BMI is a reliable indicator of body fatness for most people. While BMI does not directly measure fat, research has shown that it correlates to direct measures of body fat. Calculating your BMI should take only a few minutes.

Instructions

• 1

  Visit the Centers for Disease Control and Prevention's Adult BMI Calculator website if you are age 20 and older. For those between the ages of 2 and 19, visit the Centers for Disease Control and Prevention's BMI Calculator for Children and Teens website.

• 2

  Enter your height in feet and inches in the appropriate fields. Enter your weight in pounds in the appropriate field. Click the "Calculate" button. If you are 19 or younger, enter your birth date, date of measurement, sex, height to the nearest 1/8-inch and weight to the nearest 1/4-pound on the BMI Calculator for Child and Teen website. Click "Calculate."

• 3

  See whether you are underweight, normal, overweight or obese on the "Results" page. A BMI below 18.5 indicates you are underweight. A BMI of between 18.5 and 24.9 indicates you are in the normal weight range. A BMI of between 25 and 29.9 indicates you are overweight, while a score above 30 indicates obesity. For children and teens, your BMI is indicated as a percentile explained in the chart that appears on the webpage.