The easiest way to determine whether you're too fat is to figure out your body mass index, or BMI. More accurate measures of body fatness exist -- total body water, for example, or total body potassium -- but they're expensive and not readily available. Your BMI is a better measure of fatness than just body weight and can help identify your risk of developing certain health problems, such as coronary heart disease, type 2 diabetes, and high blood pressure.
BMI is one of the most accurate methods of relating your weight to your height. It gives health care experts a way to understand how excess body weight affects health. You are considered overweight if your BMI is greater than/equal to 25; obesity is defined as a BMI greater than/equal to 30*.
Calculate your BMI - Standard BMI Calculator
Note: This chart is for adults 20 years and older.