Calculation methodology

Each calculator asks for project measurements and choices that affect the result. Its method section explains which dimensions are used, what is included, and what the estimate leaves out.

Reference values such as pack sizes, product coverage and local rules are kept separately from calculation code. Tool pages link to the published source for those values and show when the source was checked. Country-specific tools use the local reference data and units documented for that tool.

Each calculator keeps reference data separate from arithmetic. The tool applies its stated formula to the values you enter and converts units only where the page explains that conversion. Where materials are sold in whole packs, the order quantity is rounded up to a whole pack. Display formatting may round a number for readability, it does not change the quantity used by the calculation.

The result is an estimate, not a survey or design. Check the worked example, assumptions, limits and safety notes on the tool page. Your project conditions, chosen product and local requirements may change what you need.