Source: https://guthlabs.ai/docs/instruments/paint-coverage-calculator/mechanism/

instrument mechanism / verified-clean

# Paint Coverage Calculator mechanism

The inspectable method record for Paint Coverage Calculator, kept separate from implementation and qualification.

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

## Model scope

The honest-label statement about surface porosity and application method is appropriate, but the instrument is not complete or correct for its walls/ceiling and cans-to-buy claims until ceiling-area handling, a single defined default coverage rate, unit behavior, and can-sizing/rounding rules are specified.

- The stated computation includes walls/ceiling, but the formula only sums wall areas and does not add ceiling area.

- The output 'cans to buy' has no formula and requires a can-size input plus a round-up rule.

- The default coverage rate is given as a range of 350–400 sq ft/US gal rather than one defined default value.

- The formula should explicitly constrain net paintable area to zero or greater; openings greater than wall area would produce a negative paint requirement.

## Units and conventions

- Coverage rate is assumed to be in square feet per US gallon.

- All wall and opening areas must use the same area unit before subtraction.

- Metric areas must be converted using 1 square metre = 10.7639 square feet when using a sq ft/US gal coverage rate.

- Liters are assumed to use 1 US gallon = 3.78541 liters.

- Coats are dimensionless and should be nonnegative; coverage rate must be greater than zero.

## Inspectable vector

One of 4 source-bound review vectors:

````
{
  "inputs": {
    "wall_segments": [
      {
        "width_ft": 12,
        "height_ft": 8
      },
      {
        "width_ft": 10,
        "height_ft": 8
      }
    ],
    "openings_sq_ft": 20,
    "coats": 2,
    "coverage_rate_sq_ft_per_gallon": 350
  },
  "expected_outputs": {
    "paintable_area_sq_ft": 156,
    "paint_gallons": 0.8914285714,
    "paint_liters": 3.3744226286
  },
  "working": "Wall area = (12 × 8) + (10 × 8) = 96 + 80 = 176 sq ft. Paintable area = 176 − 20 = 156 sq ft. Gallons = (156 ÷ 350) × 2 = 312 ÷ 350 = 0.8914285714 US gal. Liters = 0.8914285714 × 3.78541 = 3.3744226286 L."
}
````

## Failure boundary

**BREAK_CLAIMED** · SELF_FLAGGED

The zero-coverage input produces an undefined division and must be rejected. The specification also does not explicitly define whether openings are always nonnegative magnitudes, creating a sign-convention hazard that can change the computed volume.

## Other records

[01**Overview**](<https://guthlabs.ai/docs/instruments/paint-coverage-calculator/>)[03**Implementation**](<https://guthlabs.ai/docs/instruments/paint-coverage-calculator/implementation/>)[04**Qualification**](<https://guthlabs.ai/docs/instruments/paint-coverage-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-tranche3/tranche3-results.json`

- `BOUNDARY_HAZARD_CATALOG.json`