What this calculator measures
Body fat percentage is a far more informative measure of body composition than BMI alone. It separates total body weight into fat mass and lean mass (muscle, bone, organ, water), helping you understand whether changes on the scale reflect fat loss, muscle gain, or both.
How this calculator works
The U.S. Navy method uses height, neck circumference, and waist circumference (plus hip for women) in logarithmic formulas validated against underwater weighing. Results typically fall within a few percentage points of DEXA scans when measurements are taken consistently. Tape placement and consistency strongly affect accuracy — measure each site three times and average.
How to use your result
Track the trend over weeks and months rather than obsessing over single readings. Measure at the same time of day under consistent conditions (morning, pre-exercise, post-bathroom). Combine with scale weight and strength metrics for a complete picture. Goals like body recomposition or fat loss with muscle retention are best evaluated using body fat percentage alongside total weight.
Important limitation
Calculator results are estimates. Pregnancy, eating disorders, medical conditions, injuries, or concerning symptoms require qualified professional guidance.