Calculation methodology

Calxy pairs interactive calculators with the equations, assumptions and examples needed to check their results.

Formulas and sources

Calculation logic lives in reusable engines, separately from page descriptions. Where a model comes from a published standard or study, the calculator identifies its method and lists relevant references. Different legitimate models can yield different estimates.

Verification

We check worked examples against the calculation engine, test meaningful boundary cases, and check the rendered calculator on mobile and desktop layouts. Validation includes unsupported inputs and numerical limits. Automated checks reduce mistakes but cannot establish that every possible input is correct.

Precision and rounding

Most calculations use JavaScript floating-point numbers. Display rounding can differ from intermediate precision; an amortization schedule can also differ from a lender that rounds each monthly charge. Unit conversions use the shared unit registry. Exact definitions may still have rounded displays.

Estimates and uncertainty

A model assumes the conditions stated on its calculator page. Financial projections do not predict future returns, and health estimates do not diagnose a condition. Weather indices and building estimates also have stated limits. Check the assumptions before relying on a result.

Updates and corrections

The date on a calculator records its tracked update history; it is not a claim of independent professional review. See the editorial policy and correction information.