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Body Mass Index

Body Mass Index 

Body Mass Index or BMI is a single number which evaluates a person’s weight as compared to his or her height. It is generally used to indicate whether or not a person is developing, or already has, weight problems, and has a high relationship to how much body fat a person has.

The following mathematical formula is used to calculate the BMI:

A person’s body weight in kilograms (one kilogram = 2.2 pounds) is divided by his or her height squared.

 Instead of having to do calculations, click here for a Body Mass Index table obtained from the web site of the National Heart Lung and Blood Institute (NHLBI) of the National Institutes of Health (NIH). To use the table, a person finds his or her height the left-hand column marked Height, then moves across the table until reaching their weight in pounds. Then, by looking at the top of the table where the BMI values are given, the place on the BMI scale where the height and weight met is the person’s BMI.

It is also helpful that on the table, the BMIs are separated into the following categories:

  • Normal weight (first white area)
  • Overweight (first gray area)
  • Obese (second white area)
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  • Extreme obesity (second gray area)

See also our Section on Overweight and Obesity.