Source: https://guthlabs.ai/docs/instruments/body-fat-bmi-based-deurenberg/implementation/

instrument implementation / implementation-contract

# Body Fat % (BMI-based, Deurenberg) implementation

A source-bound implementation contract for Body Fat % (BMI-based, Deurenberg); deployment and executable qualification remain separate.

Status: **VERIFIED_CLEAN**Lifecycle: **implementation-contract**

## 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**: t2-050

**Effect**: Computation or source lookup only

## Input and validation requirements

The plain arithmetic engine can return Infinity for extreme finite JavaScript inputs, and it produces a negative body-fat estimate at the zero boundary instead of rejecting nonphysical inputs.

## 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": {
    "BMI": 22,
    "age": 30,
    "sex": 0,
    "sex_encoding": "female=0, male=1"
  },
  "expected_outputs": {
    "body_fat_percent": 27.9
  },
  "working": "BF% = 1.20×22 + 0.23×30 − 10.8×0 − 5.4\n= 26.4 + 6.9 − 0 − 5.4\n= 33.3 − 5.4\n= 27.9%"
}
````

## Other records

[01**Overview**](<https://guthlabs.ai/docs/instruments/body-fat-bmi-based-deurenberg/>)[02**Mechanism**](<https://guthlabs.ai/docs/instruments/body-fat-bmi-based-deurenberg/mechanism/>)[04**Qualification**](<https://guthlabs.ai/docs/instruments/body-fat-bmi-based-deurenberg/qualification/>)

## 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`