Sources and formulas
We begin with project geometry and dimensional analysis: area, volume, length, counts, coverage, or repeated units. Product yield, coverage, spacing, and installation assumptions are tied to a manufacturer, government body, standards organization, or established supplier source when a defensible primary source is available. Each calculator identifies the sources used and the date they were checked.
Inputs are normalized into a single internal unit before arithmetic is performed. The result is then converted into the purchasing units shown to the reader. This keeps feet, inches, yards, square feet, cubic feet, gallons, bags, boxes, rolls, sheets, boards, posts, and other counts from being mixed without an explicit conversion.
Presets and rounding
A preset is used only when its meaning and source can be explained. Readers can change configurable values such as waste, coverage, density, product yield, spacing, or package size when the calculator exposes them. A preset is a planning starting point, not a claim about every brand, installation pattern, or jobsite.
We may show raw mathematical quantities for transparency, but recommended purchasing quantities round up to the next whole purchasable unit. Waste is applied where cutting, breakage, pattern alignment, selection, or installation loss makes it relevant. The page explains whether the waste factor is included and what it does not cover.
Review and assistance
Arithmetic is checked against independent examples and automated tests. Editorial review checks the formula, unit labels, assumptions, worked example, sources, safety boundary, and links. A page is reviewed again when a source changes, a product convention changes, a correction is substantiated, a calculator is modified, or a scheduled review identifies uncertainty.
AI tools may assist with outlining, language cleanup, test ideas, and consistency checks. They do not replace source verification or arithmetic tests, and generated claims are not treated as evidence. Material changes require human review before publication. See Corrections and updates for the evidence and update process.