How our calculators work
This page explains where Calcipedia's formulas come from, how assumptions are handled, and what the results can and cannot be used for.
Formula sourcing
Formulas are drawn from primary sources: published clinical guidelines, government actuarial tables, standard financial definitions, academic references, and authoritative engineering or scientific standards. Each calculator page identifies the formula used and, for sensitive topics, links to the source material.
Where multiple valid formulas exist for the same calculation — for example, the Mifflin-St Jeor versus the Harris-Benedict equation for basal metabolic rate — the calculator page names the specific formula in use and explains why it was chosen.
Assumptions and scope
Every calculator makes assumptions. A mortgage calculator assumes a fixed interest rate. A calorie calculator assumes a specific activity multiplier. A salary calculator assumes a particular tax year and jurisdiction.
For YMYL-class calculators — those covering health, body metrics, nutrition, pregnancy, and personal finance — these assumptions are disclosed in a dedicated "About this calculator" block on the page, showing the reviewed date, methodology, limitations, and disclaimer. For general calculators (maths, dates, education, utility tools), limitations and edge cases are documented within the article copy and FAQ section instead.
Country and standard scope
Some calculations are jurisdiction-specific. Salary and tax calculators state which country's rules and tax year they apply to. Mortgage calculators state the assumed rate convention and compounding period. Clinical reference ranges state the guideline body they come from.
If a calculator does not yet carry explicit country or standard notes, it is using widely applicable general formulas. We are progressively adding scope notes to all calculators where country or standard context matters.
Health and body calculators
Calculators covering BMI, body composition, calorie needs, protein requirements, pregnancy dates, and clinical estimates use formulas from recognised health authorities such as the World Health Organization (WHO), the American College of Obstetricians and Gynecologists (ACOG), the NHS, and published peer-reviewed research.
Results from these calculators are population-level estimates. They do not account for individual medical history, underlying conditions, prescribed medication, or clinical supervision. Always consult a qualified healthcare professional for personal health decisions.
Finance and salary calculators
Finance calculators use standard financial mathematics: compound interest, amortisation schedules, present and future value formulas, and annuity calculations. Salary and tax calculators use published tax band and rate data for the stated tax year and jurisdiction.
Results are indicative estimates. They do not constitute financial advice, and they cannot account for individual lender terms, fee structures, personal tax circumstances, benefit entitlements, or regulatory changes after the reviewed date shown on the page.
When to seek professional advice
Use Calcipedia calculators for orientation, comparison, and general planning. Seek professional advice before committing to a mortgage, making investment decisions, beginning a medical diet, interpreting a clinical result, or filing a tax return.
Calculator pages for sensitive topics include a reminder of when professional advice is warranted. These reminders are not legal disclaimers — they are practical guidance about the limits of any generalised estimation tool.
For the content and accuracy standards that govern how explanatory copy is written and maintained, see the editorial standards page.