How each financial calculation is built

Every page starts with a defined decision, a named equation and inputs that use consistent units and timing.

Define the decision and scope

We identify what the result is meant to explain and which adjacent questions need a different formula. Broad keyword demand does not change the mathematical boundary.

Define every equation and variable

Pages show the equation, units, period, sign convention and timing assumptions. A percentage is stored as a decimal in the calculation even when it is entered and displayed as a percentage.

Use reproducible examples

Worked examples use the displayed formula and sample inputs. Spreadsheet equivalents must reproduce the same result before they are referenced.

Test ordinary and invalid cases

Calculators are checked with ordinary, zero-denominator, negative and boundary inputs appropriate to the equation. Undefined results stop with an explanation instead of returning Infinity or a misleading zero.

Corrections

Material corrections update the page, model version and affected examples. Readers can use the source list to compare the underlying authority.