The U.S. Navy developed a way to estimate body fat with nothing but a tape measure, because calipers and lab equipment aren’t practical for assessing thousands of sailors. It is now one of the most popular at-home methods. How good is it?
The answer first
The U.S. Navy method estimates body-fat percentage from circumference measurements — neck and waist for men, plus hip for women — together with height. It is typically accurate to within about 3–4 percentage points of a DEXA scan, which is impressive for a tape measure. But because it infers fat from body shape rather than measuring it, it can be off for people with unusual proportions. Try it in the body-fat calculator.
The formula
The original equations use inches and a base-10 logarithm:
Men: %BF = 86.010 × log10(waist − neck) − 70.041 × log10(height) + 36.76
Women: %BF = 163.205 × log10(waist + hip − neck) − 97.684 × log10(height) − 78.387The waist-minus-neck term is the key idea: a bigger gap between your waist and neck implies more abdominal fat relative to frame size.
How to measure correctly
Most of the error in this method comes from sloppy measuring, not the formula. Be consistent:
| Site | Where | Notes |
|---|---|---|
| Neck | Just below the larynx | Tape sloping slightly down to the front |
| Waist (men) | At the navel | Relaxed, end of a normal breath |
| Waist (women) | Narrowest point | Usually above the navel |
| Hip (women) | Widest point of buttocks | Feet together |
Keep the tape level and snug without compressing the skin, and take each measurement two or three times, using the average.
How accurate is it, really?
Validation studies put the Navy method within roughly 3–4% of hydrostatic weighing or DEXA for typical adults. That makes it excellent for tracking change: if you measure the same way each time, a drop from 22% to 19% is meaningful even if the absolute numbers are a little off.
Where it struggles:
- Very lean people (low single-digit body fat) — the formula can read too high.
- Very muscular people — a thick neck or muscular waist can skew the estimate.
- Unusual fat distribution — someone who stores fat on the legs rather than the abdomen won’t be captured well by waist circumference.
Reference ranges
| Category | Men | Women |
|---|---|---|
| Athletic | 6–13% | 14–20% |
| Fitness | 14–17% | 21–24% |
| Average | 18–24% | 25–31% |
| High | 25%+ | 32%+ |
Women carry more essential fat than men, which is why their healthy ranges sit higher.
Using it well
Treat the Navy method as a trend tracker, not an exact reading. Combine it with the ideal body weight calculator for a fuller picture, and set calories toward your goal with the TDEE calculator and macro calculator.
A note on health
Body-fat estimates are general fitness information, not a medical diagnosis. If you have concerns about your weight or health, consult a qualified professional. See our methodology for the formula source.