Every smart scale works on the basis of BIA (Bioelectrical Impedance Analysis). A small electrical current is sent from one foot through the whole body to another one. The speed of current detects the percentage of fat, water, muscles, and bones. The matter is that current flows faster through water and muscle. Bone and fat are poor electricity conductors.

To get accurate data, people enter their gender, age, and height into the incorporated scale software or app.