How we check our calculators and templates

You should not have to take our word for the math. This page says exactly what we check, what we do not, and how you can check it yourself.

Calculators

Each free calculator has test cases worked out by hand first (a fixed input and the answer we calculated on paper), then compared with the calculator's output by an automated test that must pass before the site is published. A calculator never ships with a failing case. Each calculator page shows its formula and a worked example you can repeat with a pencil.

Templates (spreadsheets)

• Before a template is listed, the actual sold file is opened and fully recalculated in LibreOffice. Any cell that shows an error (such as #NAME? or #DIV/0!) stops the listing. This check has already caught and fixed a real defect: some formulas used newer Excel functions without the marker Excel needs, which could show #NAME? until a cell was re-entered.
• Formulas are written into the cells, not hidden. We do not protect sheets, and our spreadsheet files contain no macros.
• Every product page shows the version, the file date, the number of sheets and formulas, and a preview of the first rows of the real sheets, taken from the file itself.

AI assistance, stated plainly

We use AI tools to draft calculators, spreadsheets, guides and page text quickly. Drafts are not trusted: the numbers are checked by the methods above, and the text is checked against the worked examples. AI drafting is disclosed on every product page. We do not claim an external audit or certification, because there has not been one.

What we do not do

• We do not publish fake reviews, testimonials or sales numbers. Until there are real ones, the proof is the evidence on this page and on each product page.
• We do not give tax, legal, financial or engineering advice. Rates and limits change; check them against the official source before you rely on them.
• We do not collect personal data on this site. Calculators run in your browser.

Per field

• Trucking: IFTA, cost per mile, per diem
• Network and homelab: subnetting, PoE, UPS, power cost, oversubscription

Found a mistake?

Tell us on the contact page. Corrections are dated in the changelog.