Sources and assumptions
This is the public registry used by the calculators. “Verified” means the cited document was opened and the claim was checked. Candidate or needs-review entries are not permitted on indexable calculator pages.
Registered assumptions
| Assumption | Category | Status | Applicability | Why it matters |
|---|---|---|---|---|
| Area of one roofing square | definition | verified | global: not region-bound | A roofing square is defined as 100 square feet. This is a unit convention rather than a property of any product, so it does not vary and there is nothing to override. |
| Volume of one board foot | definition | verified | global: not region-bound | A board foot is defined as 144 cubic inches: 1 inch thick by 12 inches wide by 1 foot long. Lumber is billed on nominal dimensions, so use the nominal size when pricing. |
| Normal-weight concrete density | density | needs-review | product-specific: US | Fresh normal-weight concrete varies with mix design, aggregate and air content. Confirm against your supplier’s mix data before relying on the weight figure. |
| Yield of a 40 lb bag of concrete mix | yield | needs-review | product-specific: US | Bag yield differs between products. Read the yield printed on the bag you are actually buying and enter it here. |
| Yield of a 50 lb bag of concrete mix | yield | needs-review | product-specific: US | Bag yield differs between products. Read the yield printed on the bag you are actually buying and enter it here. |
| Yield of a 60 lb bag of concrete mix | yield | needs-review | product-specific: US | Bag yield differs between products. Read the yield printed on the bag you are actually buying and enter it here. |
| Yield of an 80 lb bag of concrete mix | yield | needs-review | product-specific: US | Bag yield differs between products. Read the yield printed on the bag you are actually buying and enter it here. |
| Default concrete overage allowance | allowance | needs-review | product-specific: US | Allowance for spillage, uneven subgrade and form deflection. Short-ordering concrete costs far more than over-ordering slightly. |
| Bulk density of common crushed stone and gravel | density | needs-review | product-specific: US | Bulk density shifts with moisture, gradation and rock type. Suppliers publish figures for their own material, so ask for it before ordering by weight. |
| Bulk density of rounded pea gravel | density | needs-review | product-specific: US | Rounded gravels pack differently from angular crushed stone. Confirm with your supplier. |
| Default compaction allowance for a compacted aggregate base | allowance | needs-review | product-specific: US | Loose aggregate loses volume when compacted, so a compacted finished depth needs more loose material than its geometry suggests. The real figure depends on the material and the compaction effort. |
| Default aggregate waste allowance | allowance | needs-review | product-specific: US | Covers spillage during delivery and spreading, and edges that need over-filling. |
| Default settling allowance for screened topsoil | allowance | needs-review | product-specific: US | Loose soil settles after placing and watering, so a finished grade needs more loose material than its geometry suggests. Settling depends heavily on the blend and its moisture content. |
| Paint spread rate on smooth, primed drywall | coverage | needs-review | product-specific: US | Spread rate is a property of the specific product and is printed on the tin. It falls sharply on porous or textured surfaces; bare drywall, masonry and stucco can take half as much area per gallon. Enter the figure from your own product data sheet. |
| Paint spread rate on textured or porous surfaces | coverage | needs-review | product-specific: US | Textured walls, wood siding, brick and stucco absorb far more paint than smooth drywall. This is a conservative starting point; use your product data sheet for the real figure. |
| Area of a 4 ft by 8 ft drywall sheet | product-dimension | needs-review | product-specific: US | A 4 ft by 8 ft sheet covers 32 square feet. Sheets are also sold in 10 ft and 12 ft lengths, and longer sheets mean fewer joints. Pick the size you are actually buying. |
| Exposed face height of a modular brick | product-dimension | needs-review | product-specific: US | Brick sizes are not standardised across regions or manufacturers, and the mortar joint thickness matters as much as the brick. Measure the brick you are buying and enter both figures. |
| Default mortar joint thickness | product-dimension | needs-review | product-specific: US | Joint thickness changes a brick count by roughly a fifth, so it is a required input rather than a hidden default. Measure an existing course or take the joint from your project specification. |
Registered sources
- Special Publication 811: Guide for the Use of the International System of Units (SI)National Institute of Standards and Technology · verified. Exact definitions of the international inch, foot, yard and avoirdupois pound, and of the US gallon as 231 cubic inches.
- Construction trade unit conventions (roofing square, board foot)Long-standing trade convention · verified. Unit conventions that are definitional rather than measured: one roofing square is 100 square feet; one board foot is 144 cubic inches.
- ASTM C94/C94M, Standard Specification for Ready-Mixed ConcreteASTM International · candidate. Ready-mixed concrete ordering, batching tolerances and yield expectations.
- ASTM C138/C138M, Standard Test Method for Density (Unit Weight), Yield, and Air Content of ConcreteASTM International · candidate. The test method that defines fresh concrete density and yield.
- Manufacturer published bag yield (product data sheets)Individual bagged-concrete manufacturers · candidate. Cubic feet of mixed concrete produced per bag, which varies by product and must be read off the specific bag being bought.
- ASTM C29/C29M, Standard Test Method for Bulk Density ("Unit Weight") and Voids in AggregateASTM International · candidate. The test method that defines aggregate bulk density.
- Gravel Roads Construction and Maintenance GuideUS Federal Highway Administration · candidate. Aggregate placement depths and compaction behaviour of gravel surfaces.
- Soil Survey Manual and soil bulk density referencesUSDA Natural Resources Conservation Service · candidate. Soil bulk density and the compaction and settling behaviour of placed soil.
- Manufacturer technical data sheets (spread rate)Individual paint manufacturers · candidate. Square feet covered per gallon for a specific product on a specific substrate. This is the authoritative figure and it is printed on the tin.
- Master Painters Institute architectural painting specification standardsMaster Painters Institute · candidate. Coating application standards, film build and substrate preparation.
- ASTM C1396/C1396M, Standard Specification for Gypsum BoardASTM International · candidate. Gypsum board dimensions, tolerances and product classes.
- GA-216, Application and Finishing of Gypsum Panel ProductsGypsum Association · candidate. Gypsum panel application, orientation and fastener spacing.
- ASTM C216, Standard Specification for Facing BrickASTM International · candidate. Facing brick dimensions, tolerances and classifications.