Concrete Volume & Bag Calculator mechanism

Model scope

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.

• 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.

Units and conventions

• 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.

Inspectable vector

One of 4 source-bound review vectors:

{
  "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."
}

Failure boundary

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.

Other records

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