An ETF expense ratio is the annual fee a fund charges, shown as a percentage of the money you have invested. A 0.14 percent ratio, the 2025 average for index equity exchange-traded funds, means about $14 a year on a $10,000 holding, taken quietly out of the fund's assets rather than billed to you. You never see a charge; the fee is already subtracted before the price you see.

That invisibility is the point to understand. Because the fee is deducted inside the fund, a lot of investors never check it, and over decades a difference of a few hundredths of a percent compounds into real money.

What an expense ratio is

The expense ratio bundles the fund's running costs: the manager's fee, administration, custody, legal and accounting. It is expressed as an annual percentage of assets and accrued daily, so a fund quoting 0.10 percent takes roughly one ten-thousandth of your balance each day, adding up to about a tenth of a percent over a year.

It is not a one-off charge and not a trading commission. It is an ongoing drag that applies every year you hold the fund, in good years and bad. A fund that returns 7 percent before fees and charges 0.50 percent returns 6.5 percent to you.

How small percentages compound against you

The reason a tiny number matters is time. On a $10,000 investment growing at 7 percent a year for 30 years, a 0.03 percent fee costs you roughly a few hundred dollars in total; a 1 percent fee costs several thousand, because the money taken in fees is money that never compounds. The gap widens the longer you hold and the larger the balance.

This is why index funds built the low-cost case. As a plain comparison, the Vanguard S&P 500 ETF charges 0.03 percent a year, while the older SPDR S&P 500 ETF charges about 0.0945 percent. Both track the same index with near-identical returns, so on a $10,000 holding the first costs about $3 a year and the second about $9. The structural difference between the fund wrappers is covered in ETF vs mutual fund.

What counts as cheap in 2026

The Investment Company Institute, the fund industry's trade body, reported that the asset-weighted average expense ratio for index equity ETFs held at 0.14 percent in 2025, and that index bond ETFs edged down to 0.09 percent. Both have fallen sharply over the past decade, the equity figure down about a third and the bond figure down by half across nine years.

Against that backdrop, anything at or below roughly 0.10 percent for a broad index fund is cheap, and the very largest index ETFs sit well under that, some at 0.03 percent. Actively managed and niche or thematic ETFs run far higher, often 0.50 percent and up. By way of comparison, the ICI put the average for equity mutual funds at 0.40 percent in 2025.

What the ratio does not include

The expense ratio is the main cost but not the only one. Buying and selling an ETF on an exchange can carry a bid-ask spread, the small gap between the buy and sell price, which matters more for thinly traded funds. Some brokers charge a trading commission, though many now offer commission-free ETF trades. And the ratio does not capture the fund's internal trading costs, which are real but not reported in the headline number.

None of these usually rivals the expense ratio for a buy-and-hold investor in a large, liquid fund, but they are the reason the quoted fee is a floor on cost, not the whole of it.

Where the fee buys you something, and where it does not

The fee gap between index and active funds is wide, and the question is whether the active fund earns it. The ICI put the 2025 asset-weighted average for equity mutual funds at 0.40 percent, against 0.14 percent for index equity ETFs, and many active and thematic ETFs charge 0.50 percent or more. A higher fee is only worth it when the fund reliably does something a cheap index fund cannot, such as access a market that is hard to index or follow a strategy with a genuine edge.

The evidence on that is not encouraging for the average active fund. Year after year, most actively managed funds trail their benchmark index once fees are counted, and the longer the period measured, the larger the share that fall behind. That does not make every active fund a poor choice, but it does mean a high expense ratio starts the fund in a hole it has to climb out of every single year.

How to find and compare it

Every fund publishes its expense ratio in its prospectus and on its fact sheet, and brokerage pages list it on the fund's summary. The number is quoted in percent or in basis points, where one basis point is a hundredth of a percent, so 0.14 percent is 14 basis points. For more on that unit, see what is a basis point.

When two funds track the same index, the expense ratio is often the clearest difference between them, because their returns before fees are nearly the same. No one was interviewed for this explainer; the figures come from the ICI's 2025 fee study and the funds' own published data.

What to watch

Read the expense ratio as an annual percentage you pay regardless of performance, then weigh it against what the fund does. A low fee on a broad index fund is doing its job quietly. A high fee is only worth paying if the fund is doing something a cheap index fund cannot, and the evidence that most active funds beat their benchmark after fees over long periods is thin. Check the ratio before you buy, and check it again if a provider changes it.