The US Navy method estimates body fat percentage from a tape measure and a scale. It needs no lab, no scan, and no appointment, yet it tracks within a few points of far more expensive techniques for most people.
Your visual report appears here
Fill in the form and press Calculate. You will get your number, an interpretation chip, and a personalized chart pack drawn instantly in your browser.
- Risk spectrum with your position marked
- Reference ranges from the original publication
- Shareable link, nothing stored
Scientific references
Why the military trusts a tape measure
The Navy needed a body fat method that worked on a ship, at scale, with minimal equipment. In the 1980s researchers at the Naval Health Research Center fitted equations against hydrostatic weighing, the underwater reference standard of that era, and found that circumference measurements predicted body density well enough for fitness standards. Men measure neck and waist, women add hips, and height anchors the whole calculation. The formula converts those numbers through logarithms into an estimated fat percentage.
What the tape is really capturing
The method works because fat storage has geography. Abdominal girth expands almost linearly with visceral and subcutaneous fat in most bodies, while the neck barely changes. Taking waist minus neck therefore isolates the trunk signal from frame size. For women the hips enter the equation since gluteofemoral fat is common and hormonally normal, which keeps the estimate honest across body types.
Healthy ranges worth knowing
The American Council on Exercise bands give useful anchors. For men, 6 to 13 percent reads as athletic, 14 to 17 as fit, 18 to 24 as average, and 25 or above as obese. Women carry more essential fat, so the same bands sit roughly 8 points higher. Age shifts the targets gently upward as well. The number that matters most for health is less the total than the trend and the distribution, which is why pairing this estimate with a waist measurement tells a fuller story.
Accuracy and honest limits
Expect an error band of roughly 3 to 4 percent either way. Very lean athletes and people at high obesity both stretch the equation past its comfort zone, and measurement technique matters more than most assume. Measure in the morning, keep the tape horizontal and snug without compressing the skin, and take each site twice. If the estimate will drive a decision you care about, a DEXA scan or a properly done skinfold session provides a firmer second opinion. For tracking change month to month, though, consistency beats precision, and the tape wins on consistency.