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Sources and assumptions

This is the public registry used by the calculators. Source-recorded means a citation and capture record exist; it does not claim the figure is current. A needs-source-check entry remains visible as a labelled starting value and can be replaced with product or supplier data in the calculator.

Registered assumptions

Registered calculator assumptions with source-record and applicability status.
AssumptionCategoryStatusApplicabilityWhy it matters
Area of one roofing squaredefinitionsource-recordedglobal: not region-boundA 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 footdefinitionsource-recordedglobal: not region-boundA 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 densitydensityneeds-source-checkproduct-specific: USFresh 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 mixyieldsource-recordedproduct-specific: USThe 0.30 ft³ default is the approximate yield published for a 40 lb bag of QUIKRETE Concrete Mix No. 1101. Use the yield printed on your own product when it differs.
Yield of a 50 lb bag of concrete mixyieldsource-recordedproduct-specific: USThe 0.375 ft³ default is the approximate yield published for a 50 lb bag of QUIKRETE Concrete Mix No. 1101. Use the yield printed on your own product when it differs.
Yield of a 60 lb bag of concrete mixyieldsource-recordedproduct-specific: USThe 0.45 ft³ default is the approximate yield published for a 60 lb bag of QUIKRETE Concrete Mix No. 1101. Use the yield printed on your own product when it differs.
Yield of an 80 lb bag of concrete mixyieldsource-recordedproduct-specific: USThe 0.60 ft³ default is the approximate yield published for an 80 lb bag of QUIKRETE Concrete Mix No. 1101. Use the yield printed on your own product when it differs.
Default concrete overage allowanceallowanceneeds-source-checkproduct-specific: USAllowance for spillage, uneven subgrade and form deflection. Short-ordering concrete costs far more than over-ordering slightly.
Bulk density of common crushed stone and graveldensityneeds-source-checkproduct-specific: USBulk 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 graveldensityneeds-source-checkproduct-specific: USRounded gravels pack differently from angular crushed stone. Confirm with your supplier.
Default compaction allowance for a compacted aggregate baseallowanceneeds-source-checkproduct-specific: USLoose 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 allowanceallowanceneeds-source-checkproduct-specific: USCovers spillage during delivery and spreading, and edges that need over-filling.
Default settling allowance for screened topsoilallowanceneeds-source-checkproduct-specific: USLoose 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 drywallcoverageneeds-source-checkproduct-specific: USSpread 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 surfacescoverageneeds-source-checkproduct-specific: USTextured 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 sheetproduct-dimensionneeds-source-checkproduct-specific: USA 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 brickproduct-dimensionneeds-source-checkproduct-specific: USBrick 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 thicknessproduct-dimensionneeds-source-checkproduct-specific: USJoint 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.
Default compacted asphalt mix densitydensityneeds-source-checkproduct-specific: USAsphalt density varies with aggregate, binder, air voids and compaction. The default is a planning value only; replace it with the density from the supplier or project mix design.

Registered sources

Documents and authorities cited by the calculator assumption registry.
SourcePublisherStatusCoverage
Special Publication 811: Guide for the Use of the International System of Units (SI)National Institute of Standards and Technologysource-recordedExact 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 conventionsource-recordedUnit 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 Internationalneeds-source-checkReady-mixed concrete ordering, batching tolerances and yield expectations.
ASTM C138/C138M, Standard Test Method for Density (Unit Weight), Yield, and Air Content of ConcreteASTM Internationalneeds-source-checkThe test method that defines fresh concrete density and yield.
QUIKRETE Concrete Mix No. 1101: product data sheetQUIKRETEsource-recordedApproximate yields for QUIKRETE No. 1101: 40 lb = 0.30 ft³, 50 lb = 0.375 ft³, 60 lb = 0.45 ft³ and 80 lb = 0.60 ft³. Other products may differ.
ASTM C29/C29M, Standard Test Method for Bulk Density ("Unit Weight") and Voids in AggregateASTM Internationalneeds-source-checkThe test method that defines aggregate bulk density.
Gravel Roads Construction and Maintenance GuideUS Federal Highway Administrationneeds-source-checkAggregate placement depths and compaction behaviour of gravel surfaces.
Mix Design Methods for Asphalt Concrete and Other Hot-Mix TypesAsphalt Instituteneeds-source-checkAsphalt mix design, density and compacted mixture properties used to convert volume to mass.
Soil Survey Manual and soil bulk density referencesUSDA Natural Resources Conservation Serviceneeds-source-checkSoil bulk density and the compaction and settling behaviour of placed soil.
Manufacturer technical data sheets (spread rate)Individual paint manufacturersneeds-source-checkSquare 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 Instituteneeds-source-checkCoating application standards, film build and substrate preparation.
ASTM C1396/C1396M, Standard Specification for Gypsum BoardASTM Internationalneeds-source-checkGypsum board dimensions, tolerances and product classes.
GA-216, Application and Finishing of Gypsum Panel ProductsGypsum Associationneeds-source-checkGypsum panel application, orientation and fastener spacing.
ASTM C216, Standard Specification for Facing BrickASTM Internationalneeds-source-checkFacing brick dimensions, tolerances and classifications.

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