How the Navy method works — and how to measure
The U.S. Navy circumference method, developed at the Naval Health Research Center, estimates body-fat percentage from a few tape measurements and your height. The logic is simple: where your body stores fat (waist, hips) and where it doesn't (neck) changes the ratio between those circumferences in a predictable way. The Navy still uses it for fitness assessments precisely because it needs nothing but a tape measure — no lab, no electrodes, no calipers technique to master.
Accuracy lives and dies on how you measure. Use a flexible (cloth or fiberglass) tape, keep it level with the floor, snug against the skin without compressing it, and take each measurement twice — if the two differ, measure again:
- Neck — just below the larynx (Adam's apple), sloping slightly downward to the front. Don't flare the tape over the trapezius.
- Waist — at navel level for men; at the narrowest point of the torso for women. Measure at the end of a normal exhale, belly relaxed. No sucking in.
- Hip (women only) — around the widest part of the hips and glutes, feet together.
The formulas
The method uses base-10 logarithms of the circumferences (all values in centimetres):
When you enter your age and weight, the calculator also shows the Deurenberg (1991) estimate — a BMI-based formula from a large validation study, useful as a second opinion:
Expect the two estimates to disagree by a few points — they measure different proxies. If you carry a lot of muscle, the Deurenberg number will read high for the same reason BMI does; trust the tape method more in that case.
Body-fat ranges chart
The American Council on Exercise (ACE) publishes the most widely used category ranges. Women carry more essential fat than men by design — hormones, reproduction — so the female bands sit higher across the board:
| Category | Men | Women |
|---|---|---|
| Essential fat | 2–5% | 10–13% |
| Athletes | 6–13% | 14–20% |
| Fitness | 14–17% | 21–24% |
| Average | 18–24% | 25–31% |
| Obese | 25%+ | 32%+ |
Note that "Fitness" and "Average" are perfectly healthy places to live. Sub-10% (men) or sub-18% (women) is a photoshoot condition, not a lifestyle — maintaining it year-round costs more than it gives most people.
How accurate is it vs DEXA or calipers?
Honest answer: the Navy method is typically within ±3–4% of a DEXA scan — good for a tape measure, but not lab precision. Calipers can do slightly better in skilled hands and worse in unskilled ones; consumer bioimpedance scales swing with hydration. The practical takeaway: consistency beats accuracy. A method that's 3% off but 3% off every time tracks your progress perfectly well. Measure the same way, at the same time of day, with the same tape — and watch the trend, not any single reading.
Tracking change over time
A single body-fat reading tells you little; the direction over weeks tells you almost everything. Pair your monthly tape session with what actually drives the number — a sensible calorie target from the calorie calculator and consistent strength training — and judge the plan on the trend line.
This is exactly what the CoachRight client app is built for: it charts your body-fat, weight and tape measurements over time, so you and your coach see the signal instead of the noise. Coaches: the trainer app tracks these check-ins across your whole roster — start a free 14-day trial.