A:Answer Hi Joe, thank you for purchasing a Beurer product. My name is Sheila from Beurer North America, and this is a great question. This information can be found in the instruction manual but I will go ahead and share it here with you. This scale works on the principle of Bioelectrical Impedance Analysis (BIA). This involves a quick calculation of body content using a harmless electric current that is not even noticeable. When measurement of the electrical resistance (impedance) is considered alongside other data (age, height, gender, and activity level), body fat percentage and other variables in the body can be estimated. I hope this answers your question and concerns. Please contact us if you have any other questions.