Methodology
How Smart Calculators builds and maintains its calculators—where the formulas come from, how often we check them, and what we deliberately don’t do.
What We Calculate
Our tools fall into four categories: financial (loans, mortgages, salary, investment returns), fitness and health (BMI, BMR, calorie and pace targets), math (percentages, ratios, conversions), and everyday utilities (dates, units, time). Financial and health calculators are Your-Money-or-Your-Life topics, so we hold them to a higher bar for sourcing and review.
Where Our Formulas Come From
We use widely accepted, published formulas rather than house-built models. Health calculators follow standards such as Mifflin–St Jeor for BMR, the WHO BMI thresholds, and ACSM guidance for running pace and energy expenditure. Financial calculators use the standard amortization formula for loans and mortgages, and reference IRS publications and OECD tax structure documents for tax-related logic. Math and utility tools follow textbook definitions. Where a calculator depends on a specific source, we name it inline on that calculator’s page.
How “Last Reviewed” Works
Most calculator and blog pages display a “Last reviewed” date. This is the date a human re-checked the formula, inputs, labels, and any cited figures against current sources—not the date the page was first written. We re-review YMYL pages more frequently than utilities, and any time a referenced rate, threshold, or guideline changes.
What We Don’t Do
We don’t give personalized financial, tax, legal, or medical advice. Results are estimates for general guidance and shouldn’t replace a qualified professional. We don’t require accounts, and we don’t collect personal data beyond what’s needed to run the site—see our Privacy Policy for details.
Report an Error
If a result looks wrong, a label is unclear, or a cited figure is out of date, please tell us. Visit our Contact page and include the calculator URL and the inputs you used—we’ll review and correct it.