Body Fat % Estimator (US Navy method) mechanism

Model scope

The listed test vectors use the commonly published US Navy equations as an explicit assumption, but the catalog specification must state the exact equations, base-10 logarithm, units, supported sex categories, domain validation, and required body-weight input before this instrument can be approved. The existing honest label is appropriate but should also state that the estimate is sensitive to measurement technique and is not a clinical body-composition measurement.

• The specification does not provide the actual sex-specific formulas, logarithm base, measurement units, or input sign/domain constraints.
• The standard US Navy body-fat formula requires waist minus neck for men and waist plus hip minus neck for women; these required expressions and sex-specific coefficients are not stated.
• Lean mass cannot be estimated from the listed inputs because body weight is missing. If intended, the usual formula is lean mass = body weight × (1 - body-fat percentage / 100).

Units and conventions

• The standard US Navy equations use inches for waist, neck, hip, and height.
• The logarithm is base 10, not the natural logarithm.
• Metric inputs must be converted to inches before applying the standard equations: inches = centimeters / 2.54.
• Sex must be restricted to the categories supported by the selected Navy equations; the specification does not define this mapping.

Inspectable vector

One of 4 source-bound review vectors:

{
  "inputs": {
    "sex": "male",
    "waist": 34,
    "neck": 15,
    "height": 70,
    "units": "inches",
    "body_weight": null
  },
  "expected_outputs": {
    "body_fat_percent": 17.51,
    "lean_mass_estimate": null
  },
  "working": "Male Navy formula assumed: BF = 86.010 × log10(waist − neck) − 70.041 × log10(height) + 36.76. waist − neck = 34 − 15 = 19. log10(19) ≈ 1.278754. 86.010 × 1.278754 ≈ 109.9856. log10(70) ≈ 1.845098. 70.041 × 1.845098 ≈ 129.2325. BF = 109.9856 − 129.2325 + 36.76 = 17.5131% ≈ 17.51%."
}

Failure boundary

BREAK_CLAIMED · SELF_FLAGGED

The specification exposes invalid-domain boundary cases that require explicit rejection, and it does not state the formula's required inch units even though unit misinterpretation changes the estimate substantially. The declared lean-mass output is also undefined without a body-weight input.

Other records

Sources and evidence

These pointers bind the page to evidence. They do not grant authority or collapse verification into deployment.

• VERIFIED_LEDGER.json
• evidence-tranche2/tranche2-results.json
• BOUNDARY_HAZARD_CATALOG.json