Guides

Every material calculator on this site ends in one shopping quantity: cubic yards, bags, bundles, sheets, or boards. These guides explain the rule behind that number. Each takes a concept a tool page can only state in a line — what a cubic yard is, why waste goes on before the round-up, where a coverage figure comes from — and walks it through in full, arithmetic shown step by step, common misreadings named.

The guides meet the same standard as the tools. Every figure in them is produced when the site is built, by the engine that runs the corresponding calculator or from the sourced data file the engines share, and each constant is introduced with its status: a manufacturer figure, a definition, a trade convention, or plain arithmetic. None is typed by hand, so a guide cannot disagree with the tool it describes — the methodology page says why that matters. The guides also keep the tools' boundary: they cover material quantities only, and none of them determines structural adequacy, code compliance, load-bearing requirements, permits, soil conditions, or pricing.

How material estimates are calculated

The five-step pipeline — geometry, coverage, waste, package rounding, user-priced cost — followed number by number through the concrete slab calculator. A 10 × 10 ft slab at 4 in is 100 sq ft × 0.3333 ft = 33.33 cu ft, or 1.23 cu yd; at 10% waste that is 1.36 cu yd, rounded up to an order of 1.5 cu yd. It shows why waste goes on before the round-up, when an exact fit buys no extra package, and how a metric entry takes the same path.

Waste factors, explained

Waste is the one input that is a judgment rather than a measurement. This guide covers the arithmetic — quantity × (1 + waste% ÷ 100) — and the status of each tool's default: trade conventions, adjustable in every form, with the masonry figure of 5% the one with a primary source (BIA Technical Note 10). It shows the rule at work across the trades, why the percentage goes on before the package rounding, and what the allowance does not cover.

Cubic feet, cubic yards, and ordering concrete

Volume is computed in cubic feet and reported in cubic yards, the unit ready-mix is sold in; one cubic yard is exactly 27 cu ft. The guide takes area and thickness to cubic feet, explains the inches-versus-feet thickness slip that inflates an order 12-fold, and follows the waste-adjusted volume to the 0.25 cu yd ordering increment — a convention to confirm with the plant.

Concrete bag yields by size

A bag's yield is the volume of concrete its manufacturer states it produces. The guide lists the 4 imperial sizes the tool offers, from the QUIKRETE Concrete Mix data sheet — an 80 lb bag yields 0.6 cu ft, a 40 lb bag 0.3 cu ft — and the 2 Canadian metric sizes the tool offers, from Target Products, whose 0.52 cu ft for a 30 kg bag is a published figure, not a pound-proportional guess. It turns a volume into a count, ceil(adjusted volume ÷ yield).

Feet, inches, and fractions on the tape

A mixed measurement such as 10 ft 6 in becomes 10.5 decimal feet before any area or volume arithmetic, while the layout tools keep lengths as whole counts of sixteenths of an inch so tape-measure sums are exact. The guide explains both conventions, when a result that cannot land on a sixteenth is rounded and flagged, and how the millimetre readout follows from the exact 25.4 mm per inch.

Roof pitch and the pitch factor

Pitch is rise per 12 in of run, and the pitch factor is computed, never looked up: √(1 + (rise ÷ 12)²), which at 6/12 is 1.118. Footprint × factor is the sloped area; divided by the 100 sq ft roofing square (a definition) it becomes squares, and at the default 3 bundles per square (a manufacturer baseline, adjustable) it becomes bundles. The guide also derives the hip and valley factor — 1.5 at the same pitch — and common-rafter length from run or span.

Stair layout and the common IRC figures

A flight is laid out from its total rise: the riser count is ⌈rise ÷ max riser⌉, the riser height is rise ÷ count, and treads are one fewer than risers. A 105 in rise needs 14 risers at 7.5 in. The default limits are commonly adopted IRC figures — a 7 3/4" maximum riser, a 10 in minimum tread, 6 ft 8 in of headroom — offered as convenience checks; local amendments vary, and a permit reviewer, not the tool, decides compliance. The guide computes no structure.

Coverage figures and where they come from

Every coverage or yield constant lives in one data file, with its source and as-of date beside it and a test pinning it. This guide walks that file: which figures are manufacturer data (bag yields, mortar coverage), which are published tables (brick counts per hundred square feet of wall), which are definitions (the roofing and siding square), which are arithmetic on a documented convention (the concrete block face), and which are adjustable defaults inside a published range (paint). It also lists what is yours to enter: flooring box coverage, tile size, gravel density.

Metric and imperial in the estimators

Both systems rest on exact definitions — a foot is 0.3048 m and an inch is 2.54 cm — so a metric entry is converted to the engine's feet and inches and the identical arithmetic runs: 3 m is 9.8425 ft. The guide explains the unit converter's exact-grain design, what each tool's imperial/metric toggle does, why metric concrete bags carry their own published yields, and why the unit converter shows six significant digits where the estimators show up to six decimals.

Board feet, explained

A board foot is length in feet × width in inches × thickness in inches ÷ 12; an 8 ft board 6 in wide and 1 in thick is exactly 4 board feet. The guide covers nominal versus dressed sizes under the PS 20 softwood lumber standard — a 2×4 dresses to 1.5 × 3.5 in — and how a cut list becomes an order with waste, whole-board rounding, and a price only you supply.

Back to the tools

Each guide links to the calculator it explains, and every page links to this hub. The full list of estimators is on the home page; the methodology page states the shared pipeline, conventions, and boundary; and the about page says who the site is for and where its numbers come from.

Nothing you enter in a calculator leaves your browser — the arithmetic runs locally. The full estimation pipeline is documented on the methodology page.