Make the method visible
Calculator pages include the formula, a worked example, and limitations. We distinguish contributions from growth, principal from interest, and gross amounts from take-home income.
Calculation conventions
Loan and debt models accrue interest monthly using the entered annual rate divided by 12. Contributions arrive at month-end. Balances are calculated with JavaScript floating-point arithmetic and displayed to two decimal places. Lender rounding and daily accrual can produce differences.
Validation
The release includes automated checks of zero-interest cases, amortization identities, savings targets, return calculations, and invalid repayment inputs. These are implementation tests, not an independent professional audit.
Editorial sources and corrections
Guides link to public primary sources when discussing concepts covered by those sources. Worked examples are illustrative arithmetic. No expert credentials or reviews are implied. Report an issue through the contact page with the tool name and example inputs.