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

instrument mechanism / verified-clean

# Lumber Board-Foot Calculator mechanism

The inspectable method record for Lumber Board-Foot Calculator, kept separate from implementation and qualification.

Status: **VERIFIED_CLEAN**Lifecycle: **verified-clean**

## Model scope

The per-board board-foot formula is standard under the stated inch/foot assumptions, but the instrument's claimed total outputs require corrected formulas: total_board_feet = ((thickness_in × width_in × length_ft) / 12) × quantity; total_cost = total_board_feet × price_per_bf. The UI should explicitly label per-board versus total board feet, identify all dimension units, identify price as currency per board foot, and disclose the currency rounding rule.

- The stated board_feet formula is correct only for one board when thickness and width are in inches and length is in feet; it omits quantity even though the instrument claims to output total board feet.

- The stated cost formula is correct only when bf means the applicable board-foot amount, but total cost must use total_board_feet = per_board_feet × quantity.

- The specification does not state whether board_feet means per-board board feet or total board feet, creating an output-definition mismatch.

## Units and conventions

- Thickness and width are measured in inches.

- Length is measured in feet; if length is entered in inches, the equivalent formula is thickness_in × width_in × length_in / 144.

- Price is currency units per board foot.

- Quantity is a nonnegative whole-number count of boards.

- Currency output should define a rounding rule, normally to two decimal places.

- The standard board-foot convention assumes rectangular lumber dimensions and uses nominal or entered dimensions consistently.

## Inspectable vector

One of 4 source-bound review vectors:

````
{
  "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."
}
````

## Failure boundary

**BREAK_CLAIMED** · SELF_FLAGGED

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.

## Other records

[01**Overview**](<https://guthlabs.ai/docs/instruments/lumber-board-foot-calculator/>)[03**Implementation**](<https://guthlabs.ai/docs/instruments/lumber-board-foot-calculator/implementation/>)[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`

- `BOUNDARY_HAZARD_CATALOG.json`