Do you want to find out what your BMI is? Use our body mass index calculator to find out. You’ve probably heard all about it, but was exactly is the BMI? The body mass index (BMI), is a controversial statistical measurement which compares a person’s weight and height. Though it does not actually measure the percentage of body fat, it may be a useful tool to estimate a healthy body weight based on how tall a person is. Due to its ease of measurement and calculation, it is the most widely used diagnostic tool to identify weight problems within a population including underweight overweight and obese individuals. From a fat loss perspective, BMI can be flawed, especially if you are starting a weight training program. As you put on lean muscle mass, your BMI may stay the same or increase slightly, indicating no progress. You can lose a great deal of fat and still be classified as overweight or obese using the BMI. Athletes and bodybuilders run into this issue often and this is the reason why getting your body fat percentage tested is the better approach to analyzing body composition.