How this calculator works
This calculator estimates body fat percentage using the original circumference-based method from Army Regulation 600-9 (AR 600-9) Appendix B, the formula the Army used for years to run the Army Body Composition Program. It uses neck, waist and height for men, adding hip for women, all in inches or converted from metric measurements. This is an estimate for general reference, not medical advice, and not an official Army Body Composition Program (ABCP) determination — those are performed by trained personnel following the regulation's exact measurement protocol.
Important: since June 2024 (ALARACT 053/2024), the Army's sole authorized tape-test method is a newer one-site formula that uses only abdominal circumference at the navel and body weight — it no longer uses the neck, waist, hip and height formula below. The age-based maximum allowable body fat percentages have not changed, but the percentage this calculator computes uses the older, superseded formula, so it will not match a soldier's current official ABCP result. This calculator is kept for reference and historical/educational comparison; always check the current regulation for the method actually in use.
The Army's formula is not the same as the US Navy method used elsewhere on this site. Both use log10 of circumference measurements, but with different coefficients, because they were developed from different research populations and validation studies. Entered against the same measurements, the two methods commonly disagree by a percentage point or more — this calculator shows both so you can see the difference directly.
The AR 600-9 formulas
Men: % body fat = 86.010 × log10(waist − neck) − 70.041 × log10(height) + 36.76Women: % body fat = 163.205 × log10(waist + hip − neck) − 97.684 × log10(height) − 78.387All circumferences and height are in inches. Waist is measured at the point of minimal abdominal circumference; hip is measured at its widest point and only enters the women's formula. AR 600-9's own printed worked examples round the intermediate log10 values to two decimal places for hand calculation, which can shift the final result by roughly half a percentage point from a full-precision computation like this calculator's — both are 'correct' in the sense of following the same formula, just at different levels of rounding.
Worked example: neck 16in, waist 49in, height 69in (men)
- Waist minus neck: 49 − 16 = 33 inches.
- % body fat = 86.010 × log10(33) − 70.041 × log10(69) + 36.76.
- Computed at full precision: ≈38.57%. AR 600-9's own printed worked example, using log10 values rounded to two decimals by hand, gets 38.62%, rounded to 39%.
- At age 25, the AR 600-9 maximum for men aged 21-27 is 22%, so this result is well above the standard.
Frequently asked questions
How is this different from the Navy body fat method?
Both use circumference measurements and log10, but with different coefficients from different validation studies, and the Navy method includes an intermediate body-density step (the Siri equation) that the Army formula skips entirely. The two can give noticeably different percentages for the same measurements — this calculator reports both.
Why might my result differ slightly from an official Army worksheet?
The original AR 600-9's tape-test worksheets and printed charts (Figures B-1 and B-2 in the regulation) were designed for hand calculation and use rounded intermediate values. This calculator uses full floating-point precision, which can differ from a hand-rounded result by roughly half a percentage point — and, separately, an official assessment today uses a different formula entirely (see below).
What is the maximum allowable body fat percentage?
The maximums have been 20% (men) / 30% (women) for ages 17-20, 22% / 32% for 21-27, 24% / 34% for 28-39, and 26% / 36% for age 40 and older since the original AR 600-9 (16 July 2019), and these age brackets stayed the same when the Army switched to a new measurement method in 2024. Standards have changed before and can change again — always confirm against the current regulation.
Does this calculator replace an official body composition assessment?
No, for two reasons. First, official Army Body Composition Program determinations require trained personnel, calibrated tape measures, and the regulation's exact measurement technique. Second, and more importantly, since June 2024 (ALARACT 053/2024) the Army's only authorized tape-test method is a newer one-site formula based on abdominal circumference and body weight, replacing the neck/waist/hip formula this calculator uses. This calculator implements the original AR 600-9 Appendix B formula for general estimation, education, and comparison to the Navy method only — it is not how a soldier's body fat is officially assessed today.
Why does the formula use neck and hip measurements instead of a caliper or scan?
The circumference method was chosen for the Army because it is inexpensive and fast to administer across an entire force, without needing calipers, underwater weighing, or a DEXA scan. It trades some accuracy for practicality at scale.