Published formulas
Each dedicated calculator page states the central formula or explains the conversion method used.
Methodology
How the calculators work.
Our calculation rules are documented so results can be understood, checked, and used with appropriate caution.
Calculation standards
Input validation
Tools reject invalid values such as negative loan terms, zero denominators, or missing dates instead of silently producing a misleading result.
Rounding
Money is displayed to cents and general values to four decimal places. Calculations use the unrounded JavaScript number until display.
Assumptions and limitations
Financial calculations model constant rates and regular schedules. They do not predict future returns or include every fee, tax, insurance cost, or contract term. Date calculations normalize dates to UTC to avoid daylight-saving distortions. Conversion factors are stored at greater precision than the displayed result.
Health-content policy
The BMI tool is limited to an adult screening estimate. It states that BMI is not a diagnosis, identifies important limitations, and links to a primary public-health source. It is not intended for children, teens, pregnancy, or individualized medical decisions.
Privacy and review
Calculations run locally in the browser. Pages display a method-review date and are updated when a formula, reference, limitation, or implementation changes. Last site-wide methodology review: September 25, 2026.