An expense ratio looks tiny on paper: a few hundredths of a percent here, half a percent there. But it’s charged every year, on everything you’ve built up, for as long as you hold the fund. Over decades, that adds up to real money.
This calculator shows how much. Put in what you’d invest, how long you’d stay invested and the return you want to assume, then compare two funds. It works out where each one could leave you and how much of the difference comes purely from fees.
How to use it
- Enter your amounts. What you’d start with and what you’d add each month.
- Pick a time frame. The 10, 20 and 30-year buttons are shortcuts; you can type any number of years.
- Choose a return. This is your assumption, not a prediction. Try a few to see how much the answer moves.
- Set the two expense ratios. Type them from a fund’s prospectus, or use the buttons, which are based on the fees index funds report to the SEC.
Index fund fee calculator
See how your money could grow, and how much of that growth a fund’s expense ratio takes, over 10, 20 or 30 years.
Fund A after 30 years
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Fund B after 30 years
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Extra cost of Fund B
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This is an illustration, not a forecast. You choose the yearly return; real returns go up and down and can be negative. The calculator takes the expense ratio out of the return every year, adds your monthly amount at the end of each month, and ignores taxes, trading costs and inflation. The preset expense ratios come from fees funds file with the SEC (October 2026); check a fund’s current prospectus before you invest.
Where the preset fees come from
The buttons use fee levels from our own analysis of the fee tables funds file with the SEC. The cheapest S&P 500 index fund we found charges 0.015% a year, and the typical index fund, in its cheapest share class, charges about 0.32%. S&P 500 share classes that add a 12b-1 marketing fee charge a median of about 0.60%. You'll find the details in what S&P 500 index funds really charge and in our count of U.S. index funds.
What the calculator leaves out
It assumes the same return every year, which real markets never deliver, and it doesn't include taxes, trading costs, sales loads or inflation. That keeps the comparison clean: both funds get exactly the same market, so the gap you see is the fee and nothing else. To understand what an expense ratio covers and how it's taken out of your returns, read Expense Ratios Explained.
This calculator is for general education and isn't personal investment advice. See our Financial Disclaimer.