Methodology

Calculators use established mathematical formulas or documented domain rules appropriate to the tool. The implementation and formula shown on each calculator page are the source of truth for that calculation.

Calculations retain normal floating-point precision and generally round for display rather than rounding intermediate values. Display precision is chosen to be readable for the domain; currency commonly uses a currency-style format while scientific results may retain more detail.

Inputs are parsed and checked by each calculator. Invalid numbers produce a clear error or unavailable result, units are labeled where relevant, and meaningful assumptions are shown alongside the result.

Every calculator includes assumptions and limitations. A loan estimate, health estimate, date calculation or conversion is only as useful as its inputs and the model it represents.

Tax, fees, regulatory rules, rates and other regional calculations can change by jurisdiction and year. Users should confirm the applicable location, effective period and current rules before making an important decision.

Our source philosophy prefers official government or regulatory material, recognized scientific and technical references, primary documentation and established formulas. Computation and display are separate: rounding makes an answer readable, but should not silently change the underlying calculation.

Calculators model reality and cannot cover every circumstance. If you spot a formula or content issue, use the Contact form to flag it.