How we calculate

Each calculator page has a “How this is calculated” section with the formula and a plain-language meaning for each variable. Where the method is a simulation rather than a closed formula, we describe the method instead.

Calculations keep full precision and are rounded only for display. Totals are therefore computed from unrounded figures and may differ by a unit from a sum of the rounded lines shown.

Loan payments use the standard reducing-balance formula. The Dynamic Loan Payment Calculator can also use an Actual/365 day count, which some lenders apply; we checked it against a real repayment schedule. Lenders differ in day counts, payment dates, rounding and fees, so treat results as close estimates and confirm with your lender.

Investment and retirement projections grow balances monthly at the rate you enter. Inflation is applied explicitly, and results are shown in both future money and today's money where that matters.

Returns, inflation, life expectancy and similar inputs are assumptions, not predictions. Change them to see how sensitive an outcome is. We label projections as estimates and never describe a forecast as guaranteed.

Time zone conversions use the IANA time zone database built into your browser, so daylight saving changes are handled by the rules for that place and date, never by fixed offsets.

Choosing a currency changes how amounts are displayed. We do not convert between currencies or use live exchange rates.

These tools simplify real situations. They do not model taxes, fees, penalties or product-specific rules unless a calculator says so, and they are not a substitute for advice from a qualified professional.