The Body Mass Index (BMI) Calculator can be used to calculate your BMI value and weight status while taking your age into consideration. Use the "metric units" tab if you are more comfortable with the international standard metric units. The referenced weight range and calculation formula is listed below. Your BMI is a measurement of your body weight based on your height and weight. Although your BMI does not actually "measure" your percentage of body fat, it is a useful tool to estimate a healthy body weight based on your height. Due to its ease of measurement and calculation, it is the most widely used diagnostic indicator to identify a person's optimal weight depending on his height. Your BMI "number" will inform you if you are underweight, of normal weight, overweight, or obese. However, due to the wide variety of body types, the distribution of muscle and bone mass, etc., it is not appropriate to use this as the only or final indication for diagnosis. See where you are at and find out if you are on the good side or not.