Source: https://guthlabs.ai/docs/instruments/concrete-volume-bag-calculator/
instrument / verified-clean
# Concrete Volume & Bag Calculator
The current ledger marks this instrument verified clean within the source-bound verification corpus.
Status: **VERIFIED_CLEAN**Lifecycle: **verified-clean**
## Inspectable records
[01**Overview**Purpose and lifecycle]()[02**Mechanism**Method and assumptions]()[03**Implementation**Binding and validation]()[04**Qualification**Evidence and errata]()
## Ledger state
The current ledger marks this instrument verified clean within the source-bound verification corpus.
**Area**: Everyday & Life
**Tranche**: tranche-4
**Evidence ID**: t4-019
**Ledger rows**: 1
No ledger note is attached.
## Review findings
The arithmetic formulas are standard under the stated unit assumptions, but the specification is incomplete and therefore cannot pass as written. Exact ambiguities requiring resolution are: whether dimensions are entered in feet, inches, or another unit; whether cylinder input is radius or diameter; whether bag count means fractional theoretical bags or whole bags to purchase; whether waste allowance is included; and whether approximate weight means purchased bag weight or actual concrete mass. The honest-label warning about local building-code and structural verification should remain prominent.
### Formula and scope findings
- L×W×D is correct only for rectangular-prism slabs or footings; the supported footing and slab geometries are not explicitly constrained.
- The cylinder formula πr²h is standard, but the specification must explicitly require radius input or convert a supplied diameter to radius.
- The cubic-yard output requires an explicit conversion formula: cubic_yards = cubic_feet / 27, assuming dimensions are converted to feet first.
- bags = volume / yield_per_bag gives a fractional theoretical bag count; a purchasing result must use ceil(volume / yield_per_bag), with an explicitly stated waste allowance if applicable.
- The approximate-weight output has no defined formula. The vectors assume purchased bag weight = bags_to_buy × bag_weight, which is different from the actual cured-concrete mass and should be labeled accordingly.
- Bag yield is manufacturer- and product-specific; a generic yield table must not imply that every 60 lb or 80 lb bag has the same yield.
### Unit assumptions
- All dimensions must use one consistent unit before calculating volume; the examples convert inches to feet where necessary.
- The base volume output is cubic feet when dimensions are in feet, and cubic yards are calculated as cubic_feet ÷ 27.
- Cylinder radius and height are measured in feet in the cylinder example.
- Bag yield is expressed in cubic feet per bag.
- Bag count is rounded up to the next whole bag for purchasing, with no extra waste allowance in these vectors.
- Approximate purchased material weight is calculated as whole bags purchased × nominal bag weight; it is not the finished concrete weight.
## Boundary hardening
**BREAK_CLAIMED** · SELF_FLAGGED
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.
## Errata and corrections
No applied erratum is attached to this unique-name record.
## Inspectable example
4 review vectors are recorded. One source-bound sample is shown below.
````
{
"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."
}
````
## Related workflows
[Home Renovation Estimatorslab/footings]()
## Sources and evidence
These pointers bind the page to evidence. They do not grant authority or collapse verification into deployment.
- `VERIFIED_LEDGER.json · VERIFIED_CLEAN`
- `evidence-tranche4/tranche4-results.json`
- `BOUNDARY_HAZARD_CATALOG.json`