Army Body Fat Calculator
Estimate body-fat percentage using the U.S. Army circumference-based method (AR 600-9). Uses neck, waist, height for men, and neck, waist, hips, height for women.
Last updated: September 2026
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About this calculator
The U.S. Army uses a circumference-based (tape test) body-fat estimation under AR 600-9. The formula, developed by Hodgdon and Beckett (1984) at the Naval Health Research Center, uses log-transformed girth measurements calibrated against underwater weighing.
For men: BF% = 86.010 × log10(waist − neck) − 70.041 × log10(height) + 36.76. For women: BF% = 163.205 × log10(waist + hip − neck) − 97.684 × log10(height) − 78.387.
All measurements are in inches. Waist is measured at the navel, neck just below the larynx, hips at the widest point (women only). Two measurements taken and averaged; the result is compared against the AR 600-9 age-sex table (maximums range from ~20% for men 17–20 to ~30% for men 40+, and ~30% to ~36% for women).
The tape test is not a body-composition gold standard — DEXA scans give ±1% accuracy versus ±3–5% for tape — but it is fast, cheap, and correlates well enough for compliance screening. Extremely muscular soldiers occasionally test "over" and get flagged; the AR provides a body-composition appeal path via alternative measurement.
How to use
Example — male, 70 in tall, 16 in neck, 34 in waist. BF = 86.010 × log10(34 − 16) − 70.041 × log10(70) + 36.76 = 86.010 × 1.2553 − 70.041 × 1.8451 + 36.76 = 107.98 − 129.24 + 36.76 = 15.5%. Well within Army standards for any age bracket. Example — female, 65 in tall, 12 in neck, 30 in waist, 38 in hips. BF = 163.205 × log10(30 + 38 − 12) − 97.684 × log10(65) − 78.387 = 163.205 × 1.7482 − 97.684 × 1.8129 − 78.387 = 285.29 − 177.09 − 78.387 = 29.8%. Around the AR 600-9 limit for younger age brackets, within limits for age 36+.
Frequently asked questions
How accurate is the tape test versus DEXA?
The circumference-based method has a standard error of about ±3–5% compared to underwater weighing or DEXA, which are ±1–2%. For screening it is acceptable; for research or serious body-composition tracking, use DEXA or hydrostatic weighing.
What are the Army body-fat maximums?
Under AR 600-9 (2024 edition), the maximum body-fat allowed varies by age and sex — roughly 20–26% for men and 30–36% for women, with older brackets getting slightly higher allowances. Always check the current AR 600-9 table; the standards were updated in June 2023.
Why does the formula use log-transformation?
Body fat scales nonlinearly with girth. Log-transformation of the circumference measurements produced the best fit to underwater weighing in the Hodgdon-Beckett validation study, minimizing residuals across the full 10–40% body-fat range.
Can I use this outside of Army context?
Yes. Any adult can use this as a rough body-fat estimate. It is more accurate than BMI (which counts muscle as fat) but less accurate than DEXA. For most fitness tracking purposes it is fine as a monthly reference point.