Our Methodology
Every tool is built on a single principle: the answer you get must match what you would get from the authoritative source.
Formula Sourcing
All formulas and conversion factors are sourced from primary standards bodies and official documentation. We do not guess, approximate, or copy from other calculator sites.
IRS & CFPB
Financial calculators use formulas published by official U.S. government agencies.
NIST
Unit converters rely on definitions maintained by the National Institute of Standards and Technology.
WHO
Health tools follow guidelines from the World Health Organization and peer-reviewed medical literature.
ISO Standards
International conversions and measurements reference current ISO specifications.
Testing Against Reference Values
Before any calculator goes live, we run it against a suite of known reference inputs and expected outputs. For example, our mortgage calculator is verified against the CFPB's own amortization examples. Our temperature converter is checked against NIST's official conversion tables.
Cross-validation stack
If a tool produces even a single incorrect digit, it does not ship. This redundancy catches edge cases that a single source might miss.
Regular Audits and Updates
Tax brackets change. Health guidelines evolve. Conversion standards get refined. We audit our most-used tools quarterly and the full catalog twice a year.
Formula check
Does it still match the latest standard?
Test cases
Do reference test cases still pass?
User feedback
Has anyone flagged a discrepancy?
When a discrepancy is found, we fix it within 48 hours and document the change. Tools that depend on time-sensitive data — such as tax calculators — are reviewed immediately after any relevant legislation passes.
Transparency
We believe you should know how a tool works, not just what it outputs. Where space allows, our tool pages include an explanation of the underlying formula, a worked example with real numbers, and a link to the authoritative source. If you ever want to verify our work, the path back to the primary source is always provided.
Limitations
Our tools are designed for general educational and planning purposes. They do not replace professional advice from a financial advisor, tax preparer, doctor, or engineer. Each tool page includes a disclaimer reminding users of this boundary.