A body fat meter is a widely available tool used to measure the percentage of fat in the human body. Different meters use various methods to determine the body fat to weight ratio.
In contrast with clinical tools, one relatively inexpensive type of body fat meter uses the principle of bioelectrical impedance analysis (BIA) to determine an individual's body fat percentage. To achieve this, the meter passes a small, harmless, electric current through the body and measures the resistance, then uses information on the person's weight, height, age, and sex, to calculate an approximate value for the person's body fat percentage. The calculation measures the total volume of water in the body (lean tissue and muscle contain a higher percentage of water than fat), and estimates the percentage of fat based on this information.