BMI Calculator: Weight Tracker BMI weight tracker compares your weight to your height, and is calculated by dividing your weight (in kilograms) by your height (in meters squared). It gives you an idea of whether you’re 'underweight', a 'healthy' weight, 'overweight', or 'obese' for your height. BMI and body fat calculator is one type of tool to help health professionals assess the risk for chronic disease. It is also important to understand your other risk factors. BMI Calculator is free app