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Body-Fat Measurement Methods: DEXA, Calipers, BIA & the Navy Formula

Every way to measure body fat, ranked by accuracy, plus which methods the military accepts for the secondary body-fat evaluation.

Educational reference only. The numbers on this page summarize public service regulations for planning purposes. They are not official medical, recruiting, or administrative determinations. Always confirm your status with a recruiter, commanding officer, or hiring agency using the official assessment.

DEXA (dual-energy X-ray absorptiometry)

The reference standard: a full-body X-ray scan that reports fat, lean, and bone with high precision. Accepted as a supplemental assessment under AR 600-9 where available at the installation.

Air-displacement plethysmography (Bod Pod)

Uses air displacement to measure body density. Close to DEXA in accuracy for most people and also accepted as a supplemental method under AR 600-9.

Bioelectrical impedance (BIA / InBody)

Passes a weak current through the body; the InBody 770 is explicitly named in AR 600-9 as an accepted supplemental device. Home scales using BIA are less accurate and hydration-dependent.

Skinfold calipers

Measures fat under the skin at 3–7 sites. Accurate when done by a skilled technician (±3%), less so for self-measurement. Used in NFPA fitness testing contexts.

The Navy circumference formula

The tape-only method most services use for the secondary evaluation: height, neck, waist (and hip for women) feed a validated regression. Quick and repeatable, within ±3% of DEXA for most people when measured carefully.

Estimate body fat (Navy method)

Estimate body-fat % with the exact U.S. Navy circumference formula (neck + waist; hips for women).

Result

Estimated body-fat %17.5%
±3–4% versus DXA. Women must include hip. This is the Navy method used as a cross-branch estimate; your service runs its own official assessment.

Quick answers

Which method will my branch actually use?
Typically the tape-based Navy formula. If you dispute the result, AR 600-9 allows a supplemental DXA, Bod Pod, or InBody 770 assessment where reasonably available.
How accurate are the results?
DEXA is the gold standard (±1–2%); calipers and BIA ±3% with good technique; home BIA scales are the least reliable and can swing several points with hydration.

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