Your Body Mass Index is a calculation designed to determine the percentage of your weight that is comprised of fat. A BMI between 20 and 25 is generally considered normal. This is just an estimation and body types will vary.
The calorie needs calculator is designed to allow you to enter your ideal weight and determine the number of daily calories you should eat to reach that goal. Remember to consult a physician before beginning any diet or exercise plan - particularly if you have a chronic condition.