Body Fat % Estimator (US Navy method) implementation

Binding contract

This record describes what an executable surface must bind and validate. It does not claim that a public calculator, package, or production route is deployed.

Record owner

Guth Instruments

Lifecycle

verified-clean

Evidence ID

t2-038

Effect

Computation or source lookup only

Input and validation requirements

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.

Required corrections

No binding erratum is attached to this unique-name record. Implementers must still preserve the declared units, domain, and failure behavior.

Inspectable interface fixture

The sample below is evidence for interface and validation tests, not a production implementation.

{
  "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%."
}

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