The app helps to calculate your weight without using weighing scale. The app needs your height , chest size and hip size. By using its own algorithm and calculation, the app will give the weight to the nearest. It may vary a little based on your input.
The app also has the auto mode based on the region of user and you can select your shirt size and trouser size to predict your sizes approximately. It will have some variations because the input is approx.
Size Chart correction to give more accuracy