THE NUMORIX GUIDE
How to use the Investment Fee Impact Calculator
Last reviewed September 14, 2026
What this calculator does
The engine runs two annual balances.
Formula and method
The engine runs two annual balances. With fees, it applies gross growth to the opening balance, subtracts opening balance x fee rate, then adds the annual contribution. Without fees, it adds the annual contribution first and then applies gross growth. It totals the modeled fees and defines fee impact as balance without fees minus balance with fees.
Variables and inputs
Enter Initial Investment, Annual Contribution, Annual Return Rate, Fee Rate, and Years. All money values are dollars and rates are annual percentages. Contributions are annual, and the current engine's two comparison paths place the contribution at different points in the yearly sequence.
Worked example
For $10,000 initially, a $1,000 annual contribution, 7% return, 1% fee, and one year, the with-fees path is 10,000 + 700 - 100 + 1,000 = $11,600. The no-fee path is (10,000 + 1,000) x 1.07 = $11,770, so modeled fees are $100 and fee impact is $170.
How to interpret the result
Fee impact is the difference between the two modeled ending balances, not merely the sum of explicit fee charges. Over long periods, fees also remove money that could have compounded, but in this implementation the different contribution timing also affects the comparison.
Common mistakes to avoid
Enter 1 for a 1% fee, not 0.01, and do not subtract the fee a second time from the return. Keep annual contributions separate from the starting investment. When comparing the result with another tool, check whether contributions are made at the beginning or end of each period.
Assumptions and limitations
The model uses one annual return, annual contributions, and a fee charged on the opening balance. It does not model monthly expense ratios, taxes, transaction costs, volatility, withdrawals, inflation, contribution limits, or changing fees. The no-fee path adds contributions before growth while the with-fee path adds them after growth, so the reported gap includes a timing effect as well as fee drag.