Source: https://guthlabs.ai/docs/instruments/concrete-volume-bag-calculator/implementation/

instrument implementation / implementation-contract

# Concrete Volume & Bag Calculator implementation

A source-bound implementation contract for Concrete Volume & Bag 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**: t4-019

**Effect**: Computation or source lookup only

## Input and validation requirements

The specification exposes several boundary hazards: zero dimensions can yield a numerically valid but physically meaningless zero result, zero bag yield causes an undefined division, shape selection changes the governing formula, and negative dimensions produce convention-dependent results unless explicitly rejected or normalized.

## 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": {
    "shape": "slab",
    "length": 20,
    "length_unit": "ft",
    "width": 10,
    "width_unit": "ft",
    "depth": 4,
    "depth_unit": "in",
    "bag_weight_lb": 60,
    "yield_per_bag_ft3": 0.45
  },
  "expected_outputs": {
    "volume_ft3": 66.6666666667,
    "volume_yd3": 2.4691358025,
    "raw_bags": 148.1481481481,
    "bags_to_buy": 149,
    "approximate_purchased_weight_lb": 8940
  },
  "working": "Convert depth: 4 in ÷ 12 = 1/3 ft. Volume = 20 ft × 10 ft × 1/3 ft = 200/3 = 66.6666666667 ft³. Cubic yards = 66.6666666667 ÷ 27 = 2.4691358025 yd³. Raw bags = 66.6666666667 ÷ 0.45 = 148.1481481481 bags. Whole bags = ceil(148.1481481481) = 149 bags. Approximate purchased weight = 149 × 60 lb = 8,940 lb."
}
````

## Other records

[01**Overview**](<https://guthlabs.ai/docs/instruments/concrete-volume-bag-calculator/>)[02**Mechanism**](<https://guthlabs.ai/docs/instruments/concrete-volume-bag-calculator/mechanism/>)[04**Qualification**](<https://guthlabs.ai/docs/instruments/concrete-volume-bag-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`