Calculator methodology and verification
What “verified†means here: the implementation and arithmetic have been checked against the cited source and tested with documented inputs. It does not mean a physician, lawyer, accountant, engineer or other licensed professional has approved the result unless a named reviewer is shown on that page.
Our verification workflow
- Define the user question. We document the exact output, units, jurisdiction and date sensitivity.
- Prefer primary sources. Government agencies, standards bodies, legislation, academic publications and official product documentation take priority over secondary summaries.
- Document the formula. Every retained calculator should state its equation, variables, rounding rules and assumptions.
- Test independently. We test ordinary inputs, boundary values, zero/negative handling, unit conversions and at least one hand-calculated expected result.
- Review changes. A changed formula, source, rate or regulation requires a new test and a truthful last-reviewed date.
Evidence levels
| Label | Meaning |
|---|---|
| Formula tested | Code output matches documented independent calculations. |
| Source checked | The cited primary source supports the formula or constant. |
| Expert reviewed | A named qualified reviewer has checked the page; credentials and date are displayed. |
| Estimate | Real results vary; assumptions and limitations are stated. |
High-stakes subjects
Health, legal and financial tools are excluded from search while they lack qualified review. They may remain available as educational utilities, but citations and disclaimers alone do not establish professional expertise. Users should verify consequential decisions with a licensed professional.
Corrections and testing
Report a suspected error through the contact page. Include the calculator URL, inputs, expected output and supporting source. Confirmed calculation errors receive priority correction and are recorded under our corrections policy.