Body Fat Calculator (US Navy method)
A tape measure and the 1984 US Navy equations: neck and waist (plus hips for women) and height give an estimated body fat %, fat mass and lean mass.
Estimated body fat
—
Percent body fat norms (ACE)
| Category | Women | Men |
|---|---|---|
| Essential fat | 10–13% | 2–5% |
| Athletes | 14–20% | 6–13% |
| Fitness | 21–24% | 14–17% |
| Acceptable | 25–31% | 18–24% |
| Obesity | >32% | >25% |
Table as published by the American Council on Exercise (ACE Fit, Percent Body Fat Calculator page; archived copy linked in Sources — the live page now redirects).
Common questions
How accurate is the US Navy body fat method?
In the original Navy studies the equations predicted underwater-weighing body fat with a standard error of about 3.5% body fat for men and 3.7% for women. Experienced measurers agree within about 1%. Good for tracking change; not a lab measurement.
Where exactly do I measure?
Neck just below the larynx, tape sloping slightly down to the front. Men: waist at the navel. Women: waist at the narrowest point, and hips at the widest point of the buttocks. Tape snug, not compressing, breathing out normally.
What is a healthy body fat percentage?
There is no single official cut-off. The American Council on Exercise norms are the common reference: acceptable is 25–31% for women and 18–24% for men; above 32% (women) and 25% (men) is classed as obesity.
Does the military still use this formula?
In 2023 the US Department of Defense moved to a one-site (waist) tape equation. The two-site and three-site Navy equations here are the 1984 Hodgdon–Beckett ones that most online calculators use.
How it's computed
All measurements are converted to inches. Men: %BF = 86.010 × log₁₀(waist − neck) − 70.041 × log₁₀(height) + 36.76. Women: %BF = 163.205 × log₁₀(waist + hips − neck) − 97.684 × log₁₀(height) − 78.387 (Hodgdon & Beckett 1984, Naval Health Research Center). Fat mass = weight × %BF; lean mass = weight − fat mass.
Sources
- Hodgdon JA, Beckett MB. Prediction of percent body fat for U.S. Navy men from body circumferences and height. Naval Health Research Center, 1984 (DTIC ADA143890; DTIC blocks automated checks). apps.dtic.mil
- Hodgdon JA, Beckett MB. Prediction of percent body fat for U.S. Navy women from body circumferences and height. Naval Health Research Center report 84-29, 1984. apps.dtic.mil
- Potter AW, et al. Circumference-based predictions of body fat revisited (equations as used by the US military). Front Physiol. 2022. pmc.ncbi.nlm.nih.gov
- American Council on Exercise. ACE Fit Percent Body Fat Calculator — Percent Body Fat Norms for Men and Women (archived 2023; live URL now redirects). web.archive.org
Related: BMI & waist-to-height ratio · TDEE · protein intake · GLP-1 protein (uses fat-free mass)