Source: https://guthlabs.ai/docs/instruments/bmi-calculator/implementation/

instrument implementation / implementation-contract

# BMI Calculator implementation

A source-bound implementation contract for BMI Calculator; 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**: live-source boundary

**Effect**: Computation or source lookup only

## Input and validation requirements

The hazard tests expose undefined behavior for zero height, a physically invalid but arithmetically defined zero-weight boundary, and a severe unit-convention ambiguity. The calculator must reject zero height and require unambiguous units; it should also validate nonpositive body measurements.

## 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": {
    "weight": 70,
    "weight_unit": "kg",
    "height": 175,
    "height_unit": "cm"
  },
  "expected_outputs": {
    "BMI": 22.8571428571,
    "WHO_category": "Normal"
  },
  "working": "Height: 175 cm x 0.01 m/cm = 1.75 m. Height squared: 1.75 x 1.75 = 3.0625 m². BMI: 70 kg / 3.0625 m² = 22.8571428571. Since 18.5 <= 22.8571428571 < 25.0, category = Normal."
}
````

## Other records

[01**Overview**](<https://guthlabs.ai/docs/instruments/bmi-calculator/>)[02**Mechanism**](<https://guthlabs.ai/docs/instruments/bmi-calculator/mechanism/>)[04**Qualification**](<https://guthlabs.ai/docs/instruments/bmi-calculator/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/batch10-output.jsonl`