Calculator Methodology

A documented formula on every page

Every calculator page shows the exact formula used, a methodology explanation, step-by-step worked examples, and the rounding rules applied to results. There are no black-box calculators here.

Independent verification before release

Every formula is checked by an independent test oracle that compares calculator output against hand-computed cases, including edge cases and mathematical invariants. A calculator is only released when all of its cases pass.

Computation on your device

Calculation happens client-side in your browser: your inputs are never sent to our servers and are never stored by us. Losing connectivity after the page loads does not stop the calculator.

Known limits

Results are estimates and are rounded for display under rules declared on each page. Calculators that depend on variable rates (such as tax) ask you to enter the rate yourself rather than assuming one that may be wrong for your jurisdiction. We do not use live exchange rates at this stage — see the Disclaimer.