Tape Test vs DXA: Which Body-Fat Number Is Real?
How the circumference tape method compares to DXA, Bod Pod, and BIA for accuracy — and which the military accepts.
By The VivMetric Editorial Team · independent editorial research project
Accuracy ranked
DEXA is the reference standard (±1–2%). Bod Pod is close. Calipers and BIA are ±3% with good technique; home BIA scales are the least reliable and hydration-dependent. The tape (Navy) method is ±3–4% versus DXA when measured carefully.
What the military accepts
The tape is the routine secondary evaluation. DXA, Bod Pod, and InBody 770 are accepted supplements where available (AR 600-9) when a soldier disputes the tape. Home scales are not.
Source
AR 600-9 supplemental methods; On December 18, 2025, the U.S. Department of Defense (memo "Additional Guidance on Military Fitness Standards") replaced traditional height-and-weight tables across the joint force with a Waist-to-Height Ratio (WHtR) screen, effective January 1, 2026. A WHtR below 0.55 passes the initial screen; at or above 0.55, a service member receives a secondary body-fat evaluation. DoD Instruction 1308.03 sets the allowable body-fat corridor: no branch may be more restrictive than 18% (men) / 26% (women) or more lenient than 26% (men) / 36% (women). Members are assessed twice per year. Data retrieved 2026-08-19.
Run the Navy formula
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
Related pages
- Metric page → /metrics/body-fat
- Standards detail → /standards
- Tool page → /tools/body-fat