Methodology

Monthly calculation order

1. Start with the opening balance.
2. Add a beginning-of-period contribution when one is due.
3. Apply the monthly equivalent of the selected nominal annual return.
4. Deduct the monthly fee from the balance after growth.
5. Add an end-of-period contribution when one is due.
6. Carry the closing balance into the next month.

Return, fees, and contributions

The monthly return is derived from the nominal annual rate and selected compounding frequency. The annual fee assumption is divided across twelve months. Contribution timing and frequency determine which months receive a contribution.

Annual detail and inflation

The annual table groups monthly results into twelve-month periods and includes a final partial period when needed. The inflation-adjusted final value discounts the modeled final balance using the entered annual inflation rate over the exact duration.

Precision and display

Calculations retain full JavaScript numeric precision. Currency results are formatted for display to two decimal places using the selected number-format locale; changing locale or currency label does not change the underlying calculation.

Limitations

The model assumes the entered rates remain constant. It does not model taxes, volatility, sequence risk, product rules, exchange-rate movements, insolvency, or individual circumstances. Results are estimates, not forecasts or guarantees.