Source: https://guthlabs.ai/docs/instruments/lumber-board-foot-calculator/implementation/

instrument implementation / implementation-contract

# Lumber Board-Foot Calculator implementation

A source-bound implementation contract for Lumber Board-Foot 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**: t4-031

**Effect**: Computation or source lookup only

## Input and validation requirements

The extreme-magnitude vector causes the JavaScript-style arithmetic to overflow to Infinity during thickness × width, so the calculator needs finite-input validation or explicit overflow handling. The specification also has no actual formula branch despite a branch-switch hazard probe.

## 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": {
    "thickness_in": 1,
    "width_in": 6,
    "length_ft": 8,
    "quantity": 10,
    "price_per_bf": 4.5
  },
  "expected_outputs": {
    "total_board_feet": 40,
    "total_cost": 180
  },
  "working": "Per-board BF = (1 × 6 × 8) / 12 = 48 / 12 = 4 BF. Total BF = 4 × 10 = 40 BF. Total cost = 40 × 4.50 = 180.00."
}
````

## Other records

[01**Overview**](<https://guthlabs.ai/docs/instruments/lumber-board-foot-calculator/>)[02**Mechanism**](<https://guthlabs.ai/docs/instruments/lumber-board-foot-calculator/mechanism/>)[04**Qualification**](<https://guthlabs.ai/docs/instruments/lumber-board-foot-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-tranche4/tranche4-results.json`