How we calculate

Every calculator on StructureCalculator follows the same process, from the reference numbers it uses to the checks it passes before it goes live. This page explains that process so you can judge how far to trust a result.

1. Start from named sources

Each calculator is built around published reference values: material densities, coverage rates, standard sizes and thicknesses, and code limits. We take these from named, checkable sources such as building codes (for example the 2024 International Residential Code for stairs and the German DIN 18065), industry associations, and manufacturer datasheets. Every calculator page lists its sources at the bottom, with a note on exactly which figure each one supports.

When sources disagree, we say so and show the range rather than picking a convenient number. When a widely repeated figure cannot be traced to a solid source, we label it as a rule of thumb.

2. Keep the math separate and tested

The math for each calculator lives in its own small module, separate from the page text. Each module has automated tests that check it against worked examples. For instance, a 10 × 10 ft area at 4 inches deep must come out at 1.235 cubic yards, and a 35° roof must come out at 70 % slope. The full test suite, over 340 checks, runs before every release. A release that breaks a single check does not go out.

3. Check the page against the calculator

Worked examples in the text, FAQ answers, and comparison tables are recalculated with the live calculator before publishing, so the numbers on the page and the numbers the tool returns agree. When we find a mismatch later, we fix the text and the date at the top of the page changes.

4. Show the allowances, never hide them

Real orders need extra for waste, cutting, compaction, and spillage. We add those allowances openly, as a separate field or a clearly labelled line in the results, and you can change them. A result never includes a hidden fudge factor.

5. Localize properly, not just translate

Our German pages work in metric units and German standards, materials, and bag sizes, such as DIN norms, 25 and 40 kg bags, and Mineralgemisch 0/32. Our Spanish pages use US units, because most Spanish-speaking visitors are buying from US suppliers. Some calculators exist only in German because they answer questions specific to German building practice.

6. Corrections

If something looks wrong, email info@structurecalculator.com. We check every report against the sources and fix confirmed errors. Recent examples: in October 2026 we corrected the stone tonnage example on the stone calculator, the gallon figure for a 48 × 13 × 21 inch aquarium, and the spacing column in the stair stringer table.

How AI is used

Some text on this site is drafted or edited with AI tools. AI is never the source of a number: every reference value comes from a cited source, every calculator is covered by the tests above, and pages are reviewed before publishing. See our Disclaimer for the limits of any online estimate.

Who is responsible

StructureCalculator is built and maintained by Amir Ameen, who reviews every calculator and release. More about the project is on the About page.