Navy Body Fat Calculator
Estimate your body fat percentage with the U.S. Navy circumference formula from neck, waist, height, and hip for women. Metric and imperial input with a body-fat category.
16.5% BF
Fitness
Note: The U.S. Navy circumference formula estimates body fat from tape measurements. It is a screening tool, not a precise lab measurement, and can be off by a few percentage points for very muscular or very lean individuals.
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How Navy Body Fat Is Calculated
The U.S. Navy body fat formula estimates percent body fat from a handful of tape (circumference) measurements plus your height. It is fast, requires only a measuring tape, and is widely used because it needs no calipers or lab equipment. This calculator applies the official equations and classifies your result into a body-fat category.
The Formulas
The equations use the base-10 logarithm of circumference measurements (in inches) and height (in inches). Men use neck and waist; women add the hip measurement.
Women: %BF = 163.205 × log10(waist + hip − neck) − 97.684 × log10(height) − 78.387
This calculator accepts metric or imperial input and converts internally — the formula itself is defined in inches.
How to Measure
- Neck: Just below the larynx, tape sloping slightly downward to the front.
- Waist (men): At the navel, horizontal, relaxed (not sucked in).
- Waist (women): At the narrowest point of the torso.
- Hip (women): At the widest point of the buttocks.
Body Fat Categories
| Category | Men | Women |
|---|---|---|
| Essential fat | 2–5% | 10–13% |
| Athletes | 6–13% | 14–20% |
| Fitness | 14–17% | 21–24% |
| Average | 18–24% | 25–31% |
| Above average | 25%+ | 32%+ |
Worked Example
A man who is 70 in tall with a 16 in neck and 34 in waist gets: 86.010 × log10(34 − 16) − 70.041 × log10(70) + 36.76 ≈ 14.7% body fat, landing in the Fitness category.
Strengths and Limits
The Navy method correlates reasonably well with lab measurements for average builds, but it can overestimate body fat for very muscular people (a thick neck and lean waist) and underestimate it for those carrying fat outside the measured sites.
Note: This is a screening estimate, not a clinical measurement. DEXA scans and hydrostatic weighing are more accurate. Use the result as a trend indicator and consult a healthcare professional for body-composition decisions.
Frequently Asked Questions
For men, %BF = 86.010 x log10(waist - neck) - 70.041 x log10(height) + 36.76. For women, %BF = 163.205 x log10(waist + hip - neck) - 97.684 x log10(height) - 78.387, with measurements in inches.
Neck just below the larynx; waist at the navel for men or the narrowest point for women; and, for women, the hip at its widest point. Keep the tape snug and level.
It correlates reasonably well with lab measurements for average builds but can overestimate body fat for very muscular people and underestimate it for others. Treat it as a screening estimate, not a clinical value.
What is the U.S. Navy body fat formula?
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