Expense Ratio Cost Calculator

The gap at 10, 20 and 30 years

Years	Fund A	Fund B	Difference	Share of B's value

Same contributions, same gross return, different fee.

Why a small fee turns into a large number

The arithmetic of an expense ratio is simple in any single year and brutal across thirty. Each year the fund grows at the gross return, then the fee is deducted from the balance:

Balance = balance x (1 + gross return), then minus balance x expense ratio

The dollar taken this year does not just disappear. It stops compounding, so at a 7% return every $1 of fee paid at the end of year one is about $7.11 of missing wealth by year thirty. That is why the total fees paid and the total damage done are different numbers, and the damage is always the larger one.

Run the defaults: $10,000 to start, $6,000 added each year, a 7% gross return and 30 years.

• Fund A at 0.75% ends at $551,902 and takes $46,862 in fees.
• Fund B at 0.03% ends at $638,942 and takes $2,068 in fees.
• The difference in ending value is $87,041.
• A hypothetical zero-fee version of the same fund ends at $642,887.

Fund A charged $46,862 and cost its investor $90,986 of final wealth, or 14.2% of everything the portfolio would otherwise have been. Fund B gave up 0.6%. The $87,041 gap between the two funds is more than fourteen years of contributions, handed over for a fee difference of 0.72 percentage points a year.

What the expense ratio leaves out

The published number is not the full cost of owning a fund. Trading commissions and spreads inside the portfolio are paid from fund assets and never appear in the expense ratio, so a high-turnover active fund costs more than its headline figure suggests. On the ETF side, the bid-ask spread you cross on the way in and out, and any persistent tracking difference against the index, add to the bill. Sales loads and 12b-1 fees are still attached to some share classes sold through advisers.

Taxes belong in the same conversation. A fund that distributes large capital gains every December costs its taxable holders real money no matter what its expense ratio says, which is one reason ETFs became the default vehicle for taxable accounts. The mechanics are in ETF vs mutual fund and tax-efficient investing.

How to use the answer

Look up the expense ratio of everything you own. It is on the fund page, in the prospectus and on any broker's fund screener. Put your actual balances and your actual fees into the calculator and see the number in dollars rather than basis points. Then check whether a broadly equivalent fund exists for less, which for plain market exposure it usually does, as covered in expense ratios explained, index funds explained and what is an ETF.

Switching inside a 401(k) or IRA usually costs nothing. In a taxable account, selling a fund with a large unrealized gain triggers tax, so the saving has to be weighed against the bill, and directing new contributions to the cheaper fund is often the better move. To see what those contributions build on their own, use the dollar-cost averaging calculator, and to see what the ending balance is worth after decades of inflation, run it through the inflation-adjusted return calculator.