The US Navy method
Developed by the United States Navy as a practical alternative to hydrostatic weighing (the "gold standard" at the time, but impractical at scale), this method estimates body fat percentage using just a measuring tape, taking the circumference of the neck, waist and — for women — hip. Validation studies show an error margin of about 3-4 percentage points compared to more precise methods (like DEXA), which is fine for personal tracking but not for clinical diagnosis.
How to measure correctly
Neck: just below the larynx, with the tape sloping slightly downward at the front. Waist: men measure at navel height; women measure at the narrowest point of the torso. Hip (women): at the widest point of the glutes. Measure without sucking in your stomach and with the tape level, not pressing into the skin.
This is an estimate and doesn't replace a professional body composition assessment (bioimpedance, DEXA, or skinfold measurements done by a trained professional).
Frequently asked questions
Why is the formula different for men and women?
Men and women store fat differently (android vs. gynoid distribution) and have different healthy body fat ranges — that's why the Navy formula uses different measurements and coefficients for each sex, including hip only in the female calculation.
Is this method as accurate as bioimpedance or DEXA?
No — it's a practical estimate with a larger error margin (about 3-4 percentage points), but it has the advantage of needing no equipment beyond a measuring tape, which makes it useful for tracking trends over time, even if not exact in absolute value.