In Step One, we're going to get some basic body composition data. You must know your body fat percent from your smart scale. If your scale instead gives you body fat mass, you can derive your body fat percent with a simple formula: 

Bodyfat percent = (body fat mass divided by bodyweight) x 100. 

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Once you have your body fat percent and your body weight, enter these values into the calculator. The critical value for us to derive is your lean body mass.