A 1% annual fee sounds tiny until you watch it compound for thirty years. Index funds win precisely because they charge a fraction of what active funds do — but even 0.2% versus 0.03% compounds into real money over decades. This calculator makes the fee visible. It takes your Monthly Investment ($), your Expected Market Return (%), and your Expense Ratio (%), then projects two futures: the Maturity Amount ($) at the full market return and the maturity at the net return after fees. The Total Fees Paid ($) is simply the gap between those two destinies.

Invest $500 monthly for 20 years at a 10% market return. With a 0.03% expense ratio you land near $379,000. At a 1% expense ratio — typical of many active funds — you land near $342,000. That $37,000 gap bought you nothing; it is the price of the fee, and the Net Wealth Gained ($) figure shows the damage net of everything.

Fees are the one component of returns you control completely. When two funds track the same index, the cheaper one wins by definition — check the expense ratio before the past performance.

With the pre-filled defaults — Monthly Investment ($) 500, Expected Market Return (%) 10, Period (years) 20, Expense Ratio (%) 0.03 — the Index Fund Calculator returns Net Return after Fees (%) 9.97, Total Amount Invested ($) 120,000.00, Maturity Amount (after fees) ($) 381,352.78, Net Wealth Gained ($) 261,352.78, Total Fees Paid ($) 1,495.67. Change any input and those results update instantly, so you can see exactly how each number you enter moves the answer.