The US Navy formula
With all measurements in inches: men % fat = 86.010 × log₁₀(waist − neck) − 70.041 × log₁₀(height) + 36.76. Women % fat = 163.205 × log₁₀(waist + hip − neck) − 97.684 × log₁₀(height) − 78.387. This calculator converts metric input to inches for you.
ACE body fat categories
| Category | Women | Men |
|---|---|---|
| Essential fat | 10–13% | 2–5% |
| Athletes | 14–20% | 6–13% |
| Fitness | 21–24% | 14–17% |
| Average | 25–31% | 18–24% |
| Obese | 32%+ | 25%+ |
Other ways to measure body fat
DEXA scans and underwater weighing are the lab references; bioimpedance scales are convenient but swing with hydration; skinfold calipers depend on the tester’s skill. The tape method sits in the middle: free, repeatable, and good enough to track change. For a quick risk check that needs only one tape measurement, try the waist-to-height ratio.
Questions people ask
How accurate is the US Navy body fat method?
Studies comparing it with DEXA or underwater weighing typically find errors of around 3–4 percentage points for most people, larger at the extremes. Measuring carefully and consistently matters more than the formula.
Where exactly do I measure?
Neck: just below the larynx (Adam’s apple), tape sloping slightly down to the front. Waist: men at the navel, women at the narrowest point, relaxed, after breathing out. Hips (women): the widest point of the buttocks. Keep the tape level and snug but not compressing the skin.
What is a healthy body fat percentage?
The American Council on Exercise lists 14–24% as fitness to average for men and 21–31% for women. Essential fat is 2–5% for men and 10–13% for women; going near those levels is not healthy long-term.
Why is women’s body fat higher?
Women carry more essential fat, in breast tissue, around the pelvis and in hormone-related stores, so all healthy ranges start higher. That’s why the formula and the categories differ by sex.
Can I use this to track progress?
Yes, and that’s where it’s most useful. Measure at the same time of day, under the same conditions, every 2–4 weeks, and watch the trend rather than any single reading.
Sources
- Hodgdon JA, Beckett MB (1984). Prediction of percent body fat for U.S. Navy men and women from body circumferences and height. Naval Health Research Center reports 84-11 and 84-29.
- American Council on Exercise (ACE). Body fat percentage categories for men and women.
- U.S. Department of Defense Instruction 1308.3. Measurement sites for the circumference method.
Every formula on VitalMetrics is listed with its original reference on Sources & methods.