Methodology

Review before publication

A tool moves through four gates before it can be published, and the build refuses to mark a page as indexable until all of them are recorded as complete:

• Technical review — the calculation is verified against an independent reference, and edge cases such as zero rates, reversed dates and invalid input are handled deliberately rather than left to produce nonsense.
• Editorial review — the explanation is original, accurate and actually useful, with no filler written to reach a length.
• SEO review — the title and description describe what the page genuinely delivers, and the page is not duplicating an existing one.
• Policy review — sources are cited, financial and other consequential tools carry the right caveats, and advertising eligibility is assessed separately from publication.

How calculations are tested

Each calculator is checked against a known-good implementation — typically a spreadsheet built independently from the same published formula, and where possible against a published worked example from an authoritative source.

The worked example shown on each tool page uses the same arithmetic the tool itself performs. That is deliberate: if the code and the explanation ever drift apart, the page contradicts itself visibly rather than failing quietly.

Structural correctness is also machine-checked where it can be. The QR encoder, for instance, is verified against the invariants of ISO/IEC 18004 — finder pattern integrity, timing pattern alternation, the fixed dark module, symbol dimensions and dark/light balance — on every build.

Data-dependent tools

Some tools rely on figures that change: cloud pricing, exchange rates, statutory amounts. For these we record the source, the date the figure was retrieved, the date it takes effect and the date a person last confirmed it was still correct. Those dates are shown on the page.

Where a figure is illustrative rather than live — as with the cloud cost planning rates — the page says so plainly and points you to the provider’s own calculator before committing budget. We do not present stale numbers as current, and we do not refresh a “last updated” date unless something was genuinely reviewed.

Choosing sources

For rules and statutory figures we use the relevant regulator or government body. For cloud and software pricing we use the provider’s own published pricing. For exchange rates we use a reputable, documented rate provider.

Consequential calculations are never sourced from marketing blogs or aggregator sites, however convenient they are to find.

Calculation, estimate, and advice

Finance, insurance, legal and health tools distinguish between the arithmetic itself, the assumptions the model holds fixed, an estimate that depends on uncertain inputs, and general information. None of them constitute professional advice, and each says so on the page rather than hiding it in terms.

AI in the process

AI assists with implementation and drafting. It is not used to generate pages at scale, and nothing reaches publication without passing the human review gates above. Producing large volumes of low-value pages would be against both our interest and Google’s policy on scaled content.

Corrections

Every tool page carries a correction link. Reports about formulas, rates, conversions, data or explanations are tracked and triaged. A confirmed correction updates the verification date and, where the change is material, is noted on the page.

Tools that turn out to be weak, duplicated or no longer useful get merged, redirected or retired. A larger site is not automatically a better one.