Visible formulas
Each calculator explains its formula, assumptions and an example. Inputs are checked before calculating. Invalid or non-finite results are not presented as usable answers.
Precision and conventions
Results display up to 8 decimal places. Calculations use the unrounded values; very small values use scientific notation. JavaScript floating-point arithmetic can introduce tiny rounding differences.
Date tools use calendar dates and explicit leap-day conventions. Unit tools identify variants such as US liquid gallons and mechanical horsepower. NIST publishes the SI conversion reference.
Scope
This edition contains 202 calculators. Country tools use their own currency, assumptions and scope. Published government sources are linked where specific rules apply. Illustrations are not bank offers or guarantees.