Body-Fat Percentage (Navy Circumference Method)
The percentage of your weight that is fat. The U.S. Navy circumference method estimates it from height, neck, waist, and hip measurements — the same approach used in many service assessments.
Data updated: 2026-08-20 (verified vs primary service regulations)
Formula
Navy method: Men: 495 ÷ (1.0324 − 0.19077·log10(waist−neck) + 0.15456·log10(height)) − 450 · Women: 495 ÷ (1.29579 − 0.35004·log10(waist+hip−neck) + 0.22100·log10(height)) − 450
Healthy range
Athletes 6–13% (men) / 14–20% (women); healthy 14–24% (men) / 21–33% (women). Military limits depend on branch, sex, and age (e.g., Army 17–20: 20% men / 30% women, rising with age).
Military & first-responder angle
Body-fat % is the secondary evaluation when a service member fails the WHtR screen. DoD Instruction 1308.03 sets the corridor: no branch stricter than 18% (men) / 26% (women), none looser than 26% / 36%.
Calculator
Estimate body-fat % with the exact U.S. Navy circumference formula (neck + waist; hips for women).
Result
About this calculator
Estimates body-fat percentage with the U.S. Navy circumference method, using neck (and waist; hips for women) measurements.
The formula
Navy method: men BF% ≈ 86.010·log10(waist−neck) − 70.041·log10(height) + 36.76; women add a hip term. Keep units consistent (inches or cm).
Frequently asked questions
Q: How accurate is it?
A: Typically ±3–4 percentage points versus a DXA scan. Treat it as an estimate, not a lab measurement.
Q: Why include hip for women?
A: The Navy formula uses hip circumference for female measurements to account for fat distribution.
Q: What is a healthy range?
A: Roughly 10–20% for men and 18–28% for women is considered fit; your service uses its own official tables.
How to read the result
A circumference estimate is a model rather than a measurement. The Navy equation was derived by fitting tape readings against a reference method across a large sample, so it reproduces the average relationship rather than the composition of any single person. Expect roughly three to four percentage points of error against a laboratory standard, and expect that error to grow for anyone whose fat distribution sits far from the average the equation was built on.
Technique moves the result more than most people expect. The neck tape goes below the larynx and slopes downward at the front, the waist tape sits at the navel, and for women the hip tape is taken at the widest point. A single inch of error on the neck measurement shifts the estimate by about a percentage point, which is how the same person can be measured twice and receive two different answers. Track change over time with one method and treat a comparison between two different methods as meaningless.
Quick answers
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