How do you find out your BMI?

To calculate body mass index, divide your weight in kilograms by height in meters squared. Thus, a person weighing 68 kilograms who is 1.65 meters tall has a BMI of 24.98, which is slightly overweight. BMI below 18.5 is considered underweight; 18.5 to 24.9 is normal; 25 to 29.9 is overweight; and 30 and above is obese, according to the Centers for Disease Control and Prevention.

BMI does not measure body fat, per se, but it mirrors direct measures of body fat. The strength of the correlation between body fat and BMI is relative to gender, race and age. Women tend to have more body fat than men with the same BMI. Older people have more body fat than younger people with the same BMI. Athletes can have a high BMI because of their increased muscle mass, explains the CDC. According to the American Heart Association, excess weight raises blood pressure, cholesterol and triglyceride levels and the risk of diabetes.

As a screening tool to measure weight and obesity, BMI is not meant to diagnose illness. The National Heart, Lung, and Blood Institute recommends assessing two other predictors of disease, including waist circumference and risk factors such as high blood pressure and level of physical activity, notes the CDC.