Body Fat Calculator
Calculate your body fat percentage using three proven methods — U.S. Navy, BMI, and Relative Fat Mass (RFM). See your lean mass, fat mass, and where you fall on the body fat chart. 100% private, runs entirely in your browser.
How Body Fat Percentage Is Calculated
Body fat percentage represents the proportion of your total weight that consists of fat tissue. This calculator uses three established estimation methods. The U.S. Navy method uses circumference measurements of your waist, neck, and hip (for females) along with height to estimate body fat through a logarithmic formula developed by Hodgdon and Beckett in 1984. The BMI method derives an estimate from your Body Mass Index, age, and gender using a regression equation. The Relative Fat Mass (RFM) method is a newer formula that uses only height and waist circumference to predict whole-body fat percentage.
Navy Method vs BMI Method vs RFM
The U.S. Navy method is generally considered the most accurate of the three because it accounts for body shape through circumference measurements rather than relying solely on weight and height. It can distinguish between muscular and overweight individuals better than BMI-based estimates. The BMI method tends to overestimate body fat in muscular people and underestimate it in older adults or those with low muscle mass. The RFM method was developed in 2018 and correlates well with DXA scan results in clinical studies, making it a strong quick-check option.
Healthy Body Fat Ranges by Age and Gender
Healthy body fat ranges differ significantly between men and women. For men, essential fat is 2-5%, athletes maintain 6-13%, fitness-level is 14-17%, average is 18-24%, and above 25% is classified as obese. For women, essential fat is 10-13%, athletes maintain 14-20%, fitness-level is 21-24%, average is 25-31%, and above 32% is classified as obese. Body fat also tends to increase naturally with age, so a 50-year-old at 20% body fat is healthier than the same percentage might suggest for a 25-year-old.
How to Measure Body Circumferences Accurately
For accurate results, use a flexible tape measure against bare skin. Measure your waist at the narrowest point, typically at the navel level. Measure your neck just below the larynx (Adam's apple), sloping slightly downward at the front. For the hip measurement (females only), measure at the widest point of the buttocks. Stand relaxed, do not suck in your stomach, and take measurements in the morning before eating for the most consistent results.
Body Fat Percentage vs BMI
BMI uses only weight and height, so it cannot distinguish between muscle and fat mass. A bodybuilder and an overweight person can have the same BMI but vastly different body fat percentages. Body fat percentage is a more direct measure of health risk because excess fat tissue — especially visceral fat around organs — is linked to heart disease, type 2 diabetes, and metabolic syndrome. For the most accurate assessment, combine multiple methods and track trends over time rather than relying on a single measurement.