How the calculator works it out
The main result is the US Navy method, which uses height and circumferences, from the equations Hodgdon and Beckett developed at the Naval Health Research Center in 1984 (reports 84-11 for men and 84-29 for women).
Alongside it you get the Army waist-to-height ratio, the Army’s standard since Army Directive 2026-13 took effect on July 7, 2026. It is the waist at the navel divided by height, and a ratio under 0.55 meets the standard. It is not a body fat percentage. If you enter your weight you also see the old Army one-site estimate from Army Directive 2023-11 and AR 600-9, Appendix B, which the Army used from June 2023 until the 2026 change.
Navy, men: % fat = 86.010 × log10(abdomen − neck) − 70.041 × log10(height) + 36.76
Navy, women: % fat = 163.205 × log10(waist + hips − neck) − 97.684 × log10(height) − 78.387
Army waist-to-height = waist at the navel ÷ height (meets the standard below 0.55)
Old Army one-site, men: % fat = −26.97 − 0.12 × weight + 1.99 × abdomen
Old Army one-site, women: % fat = −9.15 − 0.015 × weight + 1.27 × abdomen
All lengths are in inches and weight in pounds; metric entries are converted first (1 in = 2.54 cm, 1 lb = 0.45359237 kg). For the old one-site estimate, following the Army’s rules at the time, the abdomen is rounded down to the nearest half inch, weight to the nearest pound, and the result to a whole percent. The waist-to-height ratio is not rounded.
Worked examples
Navy, man: 5 ft 10 in (70 in), neck 15 in, abdomen 34 in. 86.010 × log10(19) = 109.98 and 70.041 × log10(70) = 129.23, so 109.98 − 129.23 + 36.76 = 17.5% body fat, in ACE’s fitness band.
Army waist-to-height: 5 ft 10 in (70 in) with a 37 in waist at the navel gives 37 ÷ 70 = 0.5286, shown as 0.528, under 0.55, so it meets the standard. The same person at 38.5 in gives exactly 0.550, which does not.
Old Army one-site, the two samples from AR 600-9 Table B-5: a woman with a 30 in abdomen who weighs 165 lb gets −9.15 − 2.475 + 38.1 = 26.475, recorded as 26%. A man with a 35 in abdomen who weighs 210 lb gets −26.97 − 25.2 + 69.65 = 17.48, recorded as 17%.
Measuring well
- Use a flexible, non-stretch tape. Keep it level and snug on bare skin without pressing in.
- Measure at the end of a normal breath out, without sucking in.
- Take each measurement three times and use the average. The Army’s old tape test averaged three to the nearest half inch.
- Measure at the same time of day each time if you are tracking change.
Limits
- The body fat estimates are population equations. For one person the error can be several percentage points. Very muscular people and people with a lot of fat around the hips and thighs are the most likely to be misjudged.
- The categories are the American Council on Exercise (ACE) chart, as reported by Verywell Health. They are a general fitness guide and do not change with age.
- This calculator is for adults. It is not meant for children, during pregnancy, or for an official Army or Navy assessment. Army rules change, so check the current directive with your unit.
Questions people ask
How accurate is the Navy body fat method?
It is an estimate from a regression equation, not a scan. Hodgdon and Beckett built it by comparing tape measurements with underwater weighing in Navy personnel, and tape methods can be off by a few percentage points for an individual, more if the tape is placed or pulled differently. Use it to track your own trend with the same technique, not to compare yourself with a DEXA result.
Does the Army still use the tape test?
No. Army Directive 2026-13, effective July 7, 2026, replaced the height and weight tables, the circumference tape test and supplemental body fat assessments with a waist-to-height ratio. The waist is measured at the navel and divided by height in inches, and a ratio under 0.55 meets the standard. Every Soldier is measured twice a calendar year, and a result of 0.55 or more gets a confirmation measurement by another team the same duty day.
What was the Army one-site tape test?
From Army Directive 2023-11 (June 2023) until July 2026, the Army estimated body fat from the abdomen at the navel plus body weight. The equations were men: −26.97 − 0.12 × weight + 1.99 × abdomen; women: −9.15 − 0.015 × weight + 1.27 × abdomen, with weight in pounds and the abdomen in inches. The calculator still shows this estimate for comparison, but it is no longer the Army standard.
Where do I measure?
For the Navy method men measure the abdomen at the navel and women the waist at its narrowest point, plus the hips at the widest point. The neck is measured just below the larynx (Adam’s apple). For the Army waist-to-height ratio the waist is measured at the navel (belly button).
Why do the Navy and old Army results differ?
They are different equations built from different groups of people. The 2023 Army formula uses weight instead of height and neck size, so two people with the same waist get different results if one is heavier. A gap of a few points between the two is normal and is a good reminder that both are estimates.
What is a healthy body fat percentage?
The American Council on Exercise (ACE) chart puts the average range at 25–31% for women and 18–24% for men, with 32% and over for women and 25% and over for men in the obese range. Essential fat, which the body needs to work, is about 10–13% for women and 2–5% for men. The chart is a general guide, not a medical standard.
What does the Army allow now?
Since July 7, 2026 the Army standard is a waist-to-height ratio below 0.55, one benchmark for all Soldiers. A ratio of exactly 0.55 does not meet it. The older age-based body fat limits (20% to 26% for men, 30% to 36% for women) belonged to the tape test it replaced. This calculator is a self-check; the Army’s own measurement is the one on record.