Body fat percentage is the proportion of total body weight that comes from fat tissue. Calculating it typically involves either predictive equations, skinfold measurements, bioelectrical impedance, or circumference-based formulas such as the U.S. Navy method.

For example, the U.S. Navy method estimates body fat using waist, neck, and height measurements for men, and waist, neck, hip, and height for women. Other formulas, like the YMCA or Jackson-Pollock equations, use combinations of weight, age, and skinfold thickness. These calculations provide an accessible estimate of fat mass without requiring advanced imaging.

Monitoring body fat percentage is important because excess adiposity, especially visceral fat, is linked to insulin resistance, inflammation, and higher cardiovascular risk. Conversely, very low body fat may compromise hormonal balance, immune function, and energy availability. Consistently tracking body fat percentage allows for more precise health and fitness adjustments than tracking weight alone.