Coverage figures and where they come from

Every estimator here runs the five-step pipeline the methodology page documents: geometry, coverage, waste, package rounding, user-priced cost. The coverage step — dividing a measured area or volume by what one unit of material covers or yields — is the only step that rests on a fact about a product rather than on arithmetic or your own inputs. Those facts live in one data file, each with its source and as-of date beside it, pinned by an automated test so it cannot change without a reviewed edit. This guide renders every family of constants in that file straight from the engine and says what kind of fact each is. Every figure here is a material quantity only; none determines structural adequacy, code compliance, load-bearing requirements, or engineering suitability.

The kind matters, and the data file uses the same four statuses the methodology page lists, plus published industry tables and standards for the brick counts, rebar properties, and dressed lumber sizes — values taken as printed from a trade body or a standards document rather than from one maker's data sheet, and handled exactly as a manufacturer figure is. A manufacturer figure is a product's rated coverage, taken as published — or, in the post-hole case, the maker's installation guidance: a manufacturer figure that is advice rather than coverage, shown as a labeled suggestion and never applied for you. A definition is a unit of account the trade agreed on. A trade convention is a widely used starting point with no single primary source, always adjustable. Arithmetic needs no source.

Concrete bag yields — manufacturer figures

Source: QUIKRETE Concrete Mix (Product No. 1101) product data sheet, "YIELD" section, revised October 2022, verified 2026-07-18. Yields are stated as approximate; every listed size works out to 0.0075 cu ft per pound of dry mix. The two Canadian metric sizes come from Target Products Ltd., the licensed manufacturer of QUIKRETE in western Canada ("QUIKRETE Concrete Mix" product page, verified 2026-07-21), and are rated per bag rather than derived from the pound table.

Worked: an 8 cu ft pad with 10% waste is 8.8 cu ft to place — 15 bags of 80 lb at 0.6 cu ft each, or 30 of 40 lb. In metric, a 0.25 m³ pour is 8.83 cu ft, 9.71 with waste: 19 bags of 30 kg or 23 of 25 kg. Used by the concrete bag calculator and every concrete tool that reports bags, from the footing calculator to the fence calculator.

Mortar — a manufacturer figure, stated "up to"

Source: QUIKRETE Mortar Mix (Product No. 1102) product data sheet, "YIELD" section, revised November 2020, verified 2026-07-24. One 80 lb bag lays up to 37 standard bricks or 13 standard blocks. "Up to" makes it a best case, and it is stated for standard units only — so the brick calculator shows a mortar line only for the standard size, the block calculator always does, and both figure bags on the net laid count, since breakage waste consumes no mortar.

Brick per 100 sq ft — a published table with the joint built in

Source: Brick Industry Association, Technical Note 10 "Dimensioning and Estimating Brick Masonry" (February 2009), Table 4, verified 2026-07-24. The counts assume a single-wythe wall in running or stack bond with the standard mortar joint the table assumes, so the joint is already inside each brick's share of the wall. For the Modular size the table and the nominal-face arithmetic agree exactly — 675 per 100 sq ft is 6.75 per square foot of nominal face. The other nominal sizes follow the same arithmetic within BIA's rounding: engineer modular, for one, is BIA's published count rounded to a whole brick rather than the exact arithmetic, and the table value is the one the tool uses. The non-modular sizes — standard, engineer standard, closure standard, queen, and king — are BIA's published counts for their specified faces.

Worked: a 30 × 6 ft garden wall is 180 sq ft. In standard brick that is 1,179 net bricks, 1,237.95 with 5% waste — 1,238 to buy, with 32 bags of mortar. In modular brick the same wall needs 1,276.

Concrete block face area — arithmetic on a documented convention

Convention source: CMHA (formerly NCMA) tech note CMU-TEC-001-23, Figure 2 "Nominal and Specified Unit Dimensions", verified 2026-07-24. A standard unit's nominal 16 × 8 in face is the specified unit plus one standard mortar joint, so the wall area one block covers is pure arithmetic: (16 × 8) ÷ 144 = 0.889 sq ft, or 112.5 blocks per 100 sq ft. Worked: a 40 × 4 ft wall is 160 sq ft ÷ 0.889 = 180 blocks exactly, 189 to buy at 5% waste, with 14 mortar bags. Used by the concrete block calculator.

Roofing and siding squares — definitions

A roofing square is 100 sq ft of roof and a siding square is 100 sq ft of wall — industry definitions, not measurements. Shingle spec sheets quote per-square coverage at or fractionally under the definition depending on product (Owens Corning Guide Specifications, Section 07 31 13, verified 2026-07-18); the Vinyl Siding Institute Installation Manual ("Getting Started / Estimating", verified 2026-07-24) states the siding square as the unit "for ordering purposes". Worked: 1,400 sq ft of wall minus 150 sq ft of openings is 1,250 sq ft — 12.5 squares, 13.75 with 10% waste. The siding calculator stops there unless you give it your profile's exposure and piece length, a product fact it does not keep.

Shingle bundles per square — a manufacturer baseline, adjustable

Source: Owens Corning "Fiberglass-Based Asphalt Shingles & Accessories" Guide Specifications, Section 07 31 13, verified 2026-07-18, which lists standard three-tab and common architectural lines at 3 bundles per square; GAF states the same baseline. Premium products in the same specification run higher, so the default is adjustable up to 8. Worked: a 1,200 sq ft footprint at 8/12 carries a computed pitch factor of 1.202, so the shingles cover 1,442.22 sq ft — 14.42 squares, 15.86 with 10% waste — 48 bundles at the default, 64 for a product rated at 4 per square. For cut-up roofs the tool suggests the upper end of the conventional range, 15%. Used by the roofing shingle calculator.

Drywall sheet areas — arithmetic

No external source: a sheet's face is its nominal dimensions multiplied — 4x8 = 32 sq ft, 4x10 = 40 sq ft, 4x12 = 48 sq ft. Worked: a 14 × 12 ft room with 9 ft walls has 468 sq ft of wall; minus 60 sq ft of openings, plus 10% waste, it needs 448.8 sq ft — 15 sheets of 4x8 or 10 of 4x12. Used by the drywall calculator.

Paint coverage — a default inside a published range

Sources, verified 2026-07-18: Behr states 250–400 sq ft per gallon on PREMIUM PLUS interior product pages; Sherwin-Williams' paint calculator FAQ states a range with the same top. The adjustable default of 350 sq ft per gallon sits inside both, and the field accepts 50 to 2,000 so the figure on your can wins. Worked: 56 ft of perimeter × 9 ft minus 60 sq ft of openings is 444 sq ft, 888 over 2 coats: 2.54 gallons at the default, 3 to buy; 3.55 and 4 at the bottom of the range; 2.22 and 3 at the top. Used by the paint calculator.

Rebar weight per foot — ASTM nominal properties

Source: the ASTM A615/A615M nominal figures, also published in the CRSI Manual of Standard Practice — verified 2026-07-24 against the Harris Supply Solutions rebar size chart and an ASTM-derived chart citing CRSI. They are properties of the standardized bar sizes, identical across producers; the nominal diameter is the bar number in eighths of an inch by definition.

Worked: a 12 × 10 ft slab with 3 in of edge clearance at 16 in on-center takes 8 bars one way and 9 the other, 177.5 linear feet — 185.13 lb as #5, 118.57 lb as #4. The weight is the only sourced figure on the rebar calculator; spacing, size, and clearance come from your plans, because reinforcement and bar size are design decisions the tool counts but never makes.

Dressed lumber sizes — a published standard

Source: Voluntary Product Standard PS 20-20 "American Softwood Lumber Standard" (NIST, Revision 1, October 2021), Table 3, verified 2026-07-24. Lumber is sold by nominal size and surfaced smaller; the tools default to the dressed figure and let you type rough-sawn stock.

Worked: a 20 × 14 ft deck laid with 5/4×6 boards at their dressed 5.5 in width and ⅛ in gaps needs 42.67 rows, 47 with 10% waste, at 2 boards per row from 12 ft stock — 94 deck boards. Used by the deck, post hole, and fence calculators.

Post-hole sizing — a manufacturer's installation guidance, never applied for you

Source: QUIKRETE "Setting Posts in Concrete" project guide, verified 2026-07-24: a hole 3 times the post width, at a depth of one third to one half of the post's above-ground length, plus a gravel base. It is installation guidance, not a building code — frost depth, soil, and load requirements are set by the local code official or an engineer — so the tools show it as a labeled suggestion beside user-entered hole dimensions, and the multiplier is left for you to apply to the width you enter. Worked: each of six user-entered 12 in holes 30 in deep, each holding a dressed 4x4, holds 1.96 cu ft; the post displaces 0.21, leaving 1.75 cu ft per hole and 10.5 in all — 11.56 with 10% waste, 26 bags of 60 lb. A quantity only: the tool never decides how deep a post must be set.

Mulch bags — a packaging convention

The 2 cu ft bag is the standard big-box retail size — a convention about packaging, not a material property — so the mulch calculator labels the size and prints the cubic feet for rescaling. The conversion is arithmetic, volume ÷ 2, and one cubic yard is 13.5 bags. Worked: 150 sq ft at 2 in is 25 cu ft, 26.25 with 5% waste — 14 bags, or 0.97 cu yd in bulk.

Waste defaults — trade conventions, one of them sourced

The starting percentages the tools offer are common trade conventions, not manufacturer data: no primary source publishes a universal figure, so they are labeled as such and every one is adjustable. The one primary-sourced entry is masonry, where BIA Technical Note 10's "Brick Breakage and Waste" section gives at least 5 percent as the general rule (verified 2026-07-24). How the percentage is applied — to the quantity, before the round-up — is the subject of Waste factors, explained.

What is deliberately yours to enter

Nothing product-specific beyond these industry baselines belongs in the data file, so the flooring calculator asks for the coverage printed on your box, the tile calculator derives each tile's footprint from your tile's dimensions and grout gap, and the gravel calculator shows tons only at the density your supplier quotes. Siding exposure and piece length, rebar spacing and lap, deck board gap, fastener rate, and every price are yours for the same reason. The guides index covers the other concepts behind the tools.

Frequently asked questions

Every figure on this page is compiled into the HTML at build time from the same data file the calculators import — nothing you enter on a tool page leaves your browser. The full estimation pipeline is documented on the methodology page.