Definition of Body mass index

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Body mass index: A key index for relating a person's body weight to their height. The body mass index (BMI) is a person's weight in kilograms (kg) divided by their height in meters (m) squared.

The National Institutes of Health (NIH) now defines normal weight, overweight, and obesity according to the BMI rather than the traditional height/weight charts. Since the BMI describes the body weight relative to height, it correlates strongly (in adults) with the total body fat content.

Overweight is defined as a BMI of 27.3 % or more for women and 27.8 % or more for men, according to the NIH. Obesity is defined as a BMI of 30 and above, according to the NIH. (A BMI of 30 is about 30 pounds overweight.) Note, however, that some very muscular people may have a high BMI without undue health risks.

The table below has already done the math and metric conversions. To use the table, find the appropriate height in the left-hand column. Move across the row to the given weight. The number at the top of the column is the BMI for that height and weight.