Compare an investment growth scenario
- Enter current savings and a fixed contribution paid at the end of every month.
- Enter an assumed effective annual return before the modeled fee, and a monthly horizon.
- Enter an annual portfolio fee assumption, or zero for a fee-free scenario.
- Review both projected balances and download monthly checkpoints.
Fee model and formula
Annual growth factor after the modeled fee = (1 + gross return ÷ 100) × (1 − fee ÷ 100). Its twelfth root is the equivalent monthly growth factor. This simplified fee assumption spreads annual retention evenly over months; it does not reproduce a fund’s daily expense accounting.
For monthly rate i, horizon n, initial P and monthly C, balance = P × (1 + i)n + C × [(1 + i)n − 1] ÷ i. At zero monthly growth, balance is P + C × n. The fee-free comparison uses the gross effective annual return without the modeled fee.
For 1,000 units with no new contributions, 10% gross annual return and 10% modeled annual fee over 12 months, projected value is 1,000 × 1.10 × 0.90 = 990. A fee-free projection is 1,100. The 110 difference includes both fees and the effect of retaining less money for growth.
The SEC investor bulletin on fees and expenses explains how costs can reduce portfolio growth. Our stated retention formula is an illustrative model, not a calculation of any particular fund’s charges.
Assumptions and limits
Constant return, fixed end-month contributions and one modeled ongoing percentage fee. No volatility, taxes, inflation, transaction charges, sales loads, withdrawals or other fees. If the return you enter already includes expenses, do not deduct those expenses a second time. Actual expense timing, fee bases and returns may differ.
Current savings 0–1 trillion units; contribution 0–1 billion per month; gross effective return −90% to 100%; horizon 1–600 whole months; fee 0–10%. Bounds are numeric limits, not recommendations. Negative returns and after-fee losses are supported. The fee-free difference is a balance comparison, not an itemized total of actual fees paid. Estimates are not advice or guarantees.
Privacy and export
Inputs stay in browser memory without uploads or saved financial data. CSV includes month zero and every monthly contribution total, modeled balance, fee-free balance and difference. Every row also records the starting savings, monthly contribution, gross annual return, horizon and modeled fee. Values normally export to six decimals; very small nonzero and large numbers use scientific notation. Currency display rounds, with scientific notation for tiny or huge amounts. Reset restores illustrative defaults. Undo last action restores raw inputs, currency search, accepted result and monthly checkpoint position after Reset or choosing a zero-fee scenario. Editing an input discards that recovery step.
Should I enter a net or gross return?
Enter a return before the modeled fee. If you only have a return already net of that fee, use a zero fee assumption to avoid double counting.
Does the comparison recommend an investment?
No. It explores your assumptions without fund data, risk forecasts or product selection.