Our editorial policy

Our principles

Calculators are trust instruments. A small rounding error on a mortgage page can cost a family thousands; an off-by-one in a health calculator can be more serious still. Everything we publish is guided by four non-negotiables:

• Accuracy first. We would rather delay a launch than ship a tool we aren't confident in.
• Transparency. Every formula and assumption is visible on the same page as the tool.
• Accessibility. Explanations are written for people learning the topic, not only for those who already know it.
• Independence. Our editorial decisions are not influenced by advertisers, partners or search-ranking considerations.

Authorship & review

Every calculator and article is signed by a named author, and where the subject matter requires it, a separate named reviewer. Authors are responsible for the correctness of the math and the clarity of the explanation. Reviewers check the math independently, verify the citations, and test edge cases.

Our authors are specialists — accountants, engineers, health professionals, physics teachers, licensed financial advisors — not generalist copywriters. Reviewer assignments consider both subject expertise and independence from the original author.

You can see an author's profile, credentials and public contributions on their author page.

Sources & citations

Formulas are sourced from primary references: published standards (ISO, IEC, SI, national tax codes), peer-reviewed literature, official guidance from regulators, and well-established textbooks. We avoid sourcing calculations from other online calculators.

The "Sources" block on each calculator lists exactly which references were used. When a calculation combines multiple sources (for example, a tax calculator applying both federal and state rules), each rule is cited individually.

Methodology

Every tool goes through the same build path:

1. Scope: who is this for, what question are they answering, what inputs do they realistically have?
2. Research: gather authoritative sources; identify assumptions, constants and edge cases.
3. Implementation: build the tool with unit-tested formulas, validated inputs, and accessible markup.
4. Review: independent check of the math, the copy, the sources, and the UX.
5. Publication: release with a full explanation of inputs, outputs, formula and limitations.
6. Maintenance: watch for rule changes, rate updates and user feedback; re-review at least annually.

Where a calculation depends on rapidly-changing values — exchange rates, tax brackets, interest rates — the tool displays the "as of" date clearly.

Corrections

We take corrections seriously. If you believe a calculator is producing the wrong result, please write to our editors with:

• the URL of the calculator,
• the inputs you used,
• the result you expected and why.

Verified corrections are deployed promptly. Once a tool has been corrected, a dated note is added to the page so readers know a change was made and why.

Updates & versioning

Calculator pages show a "Last reviewed" date. When laws, standards or rates change meaningfully, we update the tool and bump this date. Minor copy changes do not trigger a new review date; substantive changes to the formula or inputs do.

Use of AI tools

We may use AI tools to assist with drafting, proofreading, or summarising background material. We do not publish AI-generated calculator logic, formulas or factual claims without human verification by a named author and an independent reviewer. Full editorial accountability for every tool rests with people, not models.

Advertising & sponsorship

If we display advertising, it is clearly marked and kept visually separate from editorial content. No advertiser has any influence over which calculators we build, what results they produce, or how we describe their methodology. Sponsored content, if ever published, will be explicitly labelled as such.

Contact the editors

Questions about this policy, or about how a particular tool was built? Our editorial team is happy to hear from readers.