Who runs this site
The site is run by its owner. There is no editorial team and no named expert on these pages, and we claim no trade or engineering qualifications. The calculators are tools for estimating, not professional advice.
How the pages are made
This website is built with AI assistance and reviewed by a human. Every number on a page either comes from a source listed at the bottom of that page or is plain arithmetic that the calculator itself performs. The owner checks each calculator by hand against its formula before the page is published.
How every number is sourced and tested
- Sources. We prefer United States government sources, then standards bodies, trade associations and universities, then manufacturer data sheets. Reference websites are only supporting evidence. We never take a figure from another calculator site, a forum or an AI answer.
- When a number is uncertain. If we cannot find a trustworthy source, the number is a value you can change, and the page labels it "Typical value, not a standard".
- Rounding. Counts such as bags, rolls and sheets always round up, because you cannot buy part of one. We use a rounding method that avoids a computer error that can add one extra unit.
- Testing. Each calculator is tested against worked examples, thousands of random inputs, and a second implementation written separately in another programming language.
- Last reviewed. The date at the top of each page is when a person last checked it against its sources. It changes only when the content or numbers change.
- Local rules. Building codes and supplier products differ from place to place. Always confirm with your supplier and your local building authority.
Fixing mistakes
If a result looks wrong, tell us at [email protected]. We fix the formula, add a test that would have caught it, and update the page's review date. See the contact page and the disclaimer.