How every AskANumber calculator is built, sourced, tested, and kept honest.
When you type a question in plain English, a language model does exactly one job: translate your words into the calculator's input fields. The number you see is never generated by AI. It is computed by a deterministic formula — the same inputs always produce the same output — and that formula is printed on the page, in The math card, on every calculator.
If the language model isn't confident it understood you, it says so and asks instead of guessing. A wrong guess about your words can be corrected; a made-up number can't.
Every calculator ships with citations to the authoritative source of its method — 30 distinct primary references across 59 calculators, including the CFPB and Freddie Mac for loan math, the WHO and CDC for health metrics, NIST for unit conversion factors, the European Central Bank for currency reference rates, and the IRS for tax parameters. The references are listed on each calculator page, directly under the methodology.
Reference data shown in tables (BMI classes, tax brackets, conversion factors) is reproduced from those cited sources and date-stamped. We do not publish figures we cannot cite, and we do not display fast-moving market data as if it were static — live data (like currency rates) is labeled with its source and date.
Every formula is implemented as a pure function and covered by an automated test suite that runs before any release: contract tests for all 59 calculators (sensible defaults, live result on first paint, permalink round-trips), reference-value tests that pin outputs to independently verifiable numbers, and format tests for how results are displayed. A calculator that fails a test does not ship.
Results are computed in your browser. Your inputs are not sent to a server unless you use the plain-English ask bar, which sends only the text you typed for parsing.
Each calculator page shows a Last reviewed date. A review checks the formula against its cited source, refreshes any dated reference data (tax brackets and similar parameters are updated when the issuing agency publishes new figures), and re-runs the full test suite. Site-wide content was last reviewed on 2026-07-02.
AskANumber is built and maintained by the AskANumber team with AI-assisted drafting; every formula, figure, and claim is verified against the cited primary source before it is published.
Finance calculators are educational tools, not financial advice. They deliberately omit lender-specific fees, insurance, and product terms to keep the math transparent — use them to sanity-check a quote, not to replace one.
Health calculators compute published screening formulas (BMI, BMR, TDEE and similar). They are informational baselines, not a diagnosis, and are no substitute for a clinician who can see the whole picture.
Where a formula has known limitations, they are listed on the page in The math card under assumptions and limitations.
Found a number that looks wrong? Please report it. Verified errors are fixed promptly, the fix is covered by a new test so it cannot regress, and the page's review date is updated.