Define the question and scope
Before building or substantially updating a tool, our standard is to define the question it answers, the inputs it needs, its units, its output and its exclusions. An initial example is a starting point, not a description of your circumstances.
Country-specific rules must be identified as such. Our publishing standard is separate pages and explanations when a country changes the governing formula or logic. A display currency or a different unit does not, by itself, implement another country’s tax, benefit, mortgage or legal system. Always check the scope of the individual page.
Choose sources for the method
For official rates and rules, we prioritise the responsible government body, regulator or scheme administrator. For scientific and mathematical methods, suitable sources include recognised textbooks, standards bodies and published research appropriate to the population and use.
Other calculator websites can help us understand common user tasks, units and useful features. Agreement with competitors is not, on its own, proof that a method is correct. A source should support the actual claim, period, country and assumptions used, rather than merely discuss a similar topic.
Source links and review dates help readers check the basis of a page. A review date records a content review; it is not a promise that a rate is a live quote or that later changes cannot affect the answer.
Check calculations and interactions
Our verification standard includes independently worked examples, typical non-default inputs, relevant boundaries and invalid entries. Unit conversions need correct factors, including squared or cubed factors where the quantity requires them. Rounding and display precision should not obscure the underlying assumptions.
Browser checks should also cover switching units or modes, keeping the user’s scenario intact, clearing stale results, correcting errors, resetting, keyboard use and small screens. Where comparison tools implement the same method, shared scenarios can reveal differences that need investigation.
These checks reduce risk; they do not establish that every combination or every calculator is free of errors. A page should not be described as reviewed by a clinician, accountant or other qualified professional unless that review actually happened. We do not claim blanket professional certification for the site.
Writing and use of automation
Explanations should define unfamiliar inputs, show the method and state material limits in plain language. Worked examples should be reproducible with the calculator. We avoid invented credentials, unsupported rankings, fabricated user stories and guarantees about real-world outcomes.
Software and AI tools may assist with research organisation, code, drafting and consistency checks. Their output is not an authoritative source, an independent expert review or evidence that a calculation is correct. The publisher remains responsible for deciding what to publish and for checking factual claims against appropriate sources.
Financial and health topics
Tax, borrowing, benefits, health and similar topics need particular care because a misleading result can affect important decisions. Pages should identify the relevant country, period or population and explain exclusions, estimates and uncertainty.
A general calculator cannot assess all of your circumstances. We do not present a screening estimate as a diagnosis, an indicative repayment as a loan offer, or a rules-based estimate as an official eligibility decision. Read the limits on financial, legal and health information before relying on a result.
Reviews, errors and corrections
Changes to a method, official rule, rate, supported population or unit convention can require a new review. There is no universal refresh interval that makes every kind of calculator current. Readers should check the page’s applicable period and the linked source when timing matters.
To report an error, contact us and select “A correction or question”. Include the URL, inputs and selected mode or units, the result shown, and the expected result with a source if available. Remove personal identifiers and use a representative example for sensitive information.
We assess reports against the stated method and supporting evidence. A confirmed material issue should be corrected, qualified or taken out of use as appropriate, with affected examples and explanations checked too. For a disputed source or method, we should explain the uncertainty rather than silently treating a competitor’s result as the answer.
Advertising and editorial independence
Advertising is not enabled on the current version of the site. If introduced, ads should be clearly distinguishable from calculator inputs, Calculate buttons, results and source links. Readers should never be asked to click ads to obtain a result or support the site.
Any paid placement, sponsored article or affiliate relationship should be disclosed where the relationship is relevant. Payment must not be presented as evidence for a formula, a professional endorsement or a favourable review. Commercial enquiries can be sent through the contact page.