Editorial Policy and Methodology
Last updated: October 25, 2026
Our purpose
CalcOrigin exists to make everyday calculations faster and easier to understand. Every calculator on this site is a free, browser-based tool that shows the result and, where possible, the steps used to reach it. We do not require an account and we do not sell calculation results.
How our calculators are built
Each calculator is implemented from a published formula or a standard definition, not from a guessed rule of thumb. Before a page is published we:
- identify the authoritative source for the formula or rule (for example, a peer-reviewed paper, a government agency publication, or a recognised standards body);
- write the calculation in plain JavaScript so the method can be inspected in the page source;
- test the calculation against published worked examples and against hand calculations;
- check that unit conversions (metric, US customary, imperial) produce consistent results;
- review the explanation text for clarity and for claims that the formula cannot actually support.
Formulas and sources
Most of our calculators fall into one of four groups. The table below shows the kind of source we use for each group.
| Category | Typical source of the method |
|---|---|
| Finance and loans | Standard amortisation and compound-interest mathematics; disclosure examples published by the U.S. Consumer Financial Protection Bureau and comparable regulators. |
| Tax and payroll | Current rate schedules and publications from the relevant tax authority (for example, IRS publications for U.S. federal tax). |
| Health and fitness | Peer-reviewed equations and guidance from public health bodies such as the World Health Organization, the U.S. Centers for Disease Control and Prevention, and the National Institutes of Health. |
| Math, dates, and conversion | Standard mathematical definitions, SI conversion factors, and calendar rules (including leap-year and time-zone handling). |
Where a calculator offers more than one formula, the page names each formula and explains when one is preferred over another. We show a range rather than a single "correct" answer when the underlying research does not support a single value.
Accuracy and limitations
Calculators are models, not measurements. A result can be mathematically correct and still be a poor fit for an individual person or a specific contract. Common reasons include rounding, assumptions built into a formula, regional rules, and inputs that the model does not collect. Each calculator page lists the main limitations that apply to it. Our results are estimates for information and education; they are not financial, medical, legal, or tax advice.
Updates and corrections
We review calculators when a rate schedule, formula, or standard changes, and when a reader reports a problem. Pages that change materially receive a new "Last updated" date. If you believe a result or an explanation is wrong, please tell us which page and which inputs you used so we can reproduce it. We correct genuine errors and note material changes rather than silently replacing content.
Independence and advertising
Advertising, where present, is separated from the calculator and its explanation. Advertisers do not review, approve, or influence calculator results, rankings, or editorial text. We do not accept payment to change a calculation or to remove a limitation.
Automation and review
Some routine work, such as formatting tables, checking links, and generating sitemap entries, is assisted by software. Formulas and explanatory text are reviewed by the CalcOrigin editorial team before publication. We do not publish a calculator solely because a page template exists; each tool must have a defined method, tested inputs and outputs, and an explanation that matches what the tool actually does.
What we ask of readers
Use the calculator as a starting point, check the assumptions listed on the page, and confirm important financial or health decisions with a qualified professional who can see your full circumstances. If a page is missing a limitation or a source, tell us and we will review it.