How we work
Every tool on this site is built on a verifiable formula, backed by a primary source, and tested before it is published. This page explains exactly how that works - and what to do if you find an error.
All tools and content on calculations.tools are built, written, and maintained by Jesper Pallesen, the site's founder and sole author. Jesper has worked in SEO and software development since 2017, with a focus on technical accuracy, data-driven analysis, and clear explanation of quantitative concepts.
Because there is one author, there is one consistent quality standard across the entire site. Every tool is built using the same process, verified against the same types of sources, and held to the same threshold before publication. There is no inconsistency between contributors, and no tool is published by someone unfamiliar with the subject matter.
Read about Jesper →Every tool follows a four-step verification process before it is published. The process is designed so that the accuracy of the result is independent of memory or assumption - it must be traceable to a primary source and testable against known values.
Every formula is traced to a primary source before work begins - a peer-reviewed publication, an international standards body (ISO, NIST, WHO), a recognised academic textbook, or a national authority such as the CDC or NHS. Secondary sources are not used as the sole basis for any calculation.
The formula is validated against known reference values. For example, 0 °C must equal exactly 32 °F and 273.15 K; 1 kg must equal 2.20462 lb. Edge cases (zero, negative values, very large numbers) are tested before publication. Any discrepancy triggers a re-check against the source.
Every factual claim in the accompanying content must be traceable to a linked, publicly accessible source. Statistics, classification thresholds, and reference ranges are checked against the original publication - not secondary summaries. On health, scientific, and reference-data pages, sources are cited inline. Unit conversion factors and mathematical formulas that are definitional constants do not require a citation - the formula itself is the verifiable claim.
Before a tool goes live, the interactive output is manually tested against the reference values from step 2. The displayed formula, worked example, and reference table are all cross-checked for internal consistency. The tool is also tested on mobile.
Not all sources are equal. The following table defines which sources meet the bar for this site and which do not.
Wikipedia is used as a navigation tool to find primary sources (journal papers, institutional reports), not as a source itself. When a Wikipedia article references a primary source and that source is publicly accessible, the primary source is cited directly.
Health tools - including BMI, body fat percentage, lean body mass, and ideal weight calculators - are held to a stricter standard than general converters, because users may act on the results.
Finance tools are divided into two tiers. Accounting and profitability tools (EBITDA, gross margin, break-even) are definitional - the formula is the answer. Valuation, returns, and personal finance tools (ROI, P/E ratio, compound interest, loan payments) produce outputs that users may act on financially. The latter are held to a higher standard.
Accuracy degrades when content is left static. Conversion factors and mathematical formulas are stable, but reference data, classification thresholds, and recommended values can change.
Tools based on fixed mathematical or physical relationships (unit conversions, percentage calculations) are not time-sensitive. They are reviewed when a bug is reported or when a standards change is identified.
Classification thresholds, population norms, and clinical reference ranges are monitored against WHO, CDC, and NIH publications. Updates to these pages are made when the underlying guidance changes.
Exchange rates are provided by the Frankfurter API, which sources data from the European Central Bank. Rates are fetched live and reflect the most recent available ECB publication.
Tools are selected and built based on genuine usefulness to users - not commercial relationships. The following commitments apply to all content on this site:
If you believe a formula, result, or piece of content on this site is inaccurate, please report it. Errors are taken seriously: every report is investigated, and confirmed errors are corrected promptly.
Email info@calculations.tools with the URL of the relevant tool and a description of the issue. If you can include the expected correct result and the source you are referencing, that helps resolve it faster.