An expense ratio is the annual fee a fund — such as an ETF or index fund — charges to cover its running costs, expressed as a percentage of the money you have invested. A 0.10% expense ratio works out to $10 a year on every $10,000 held. It is never billed separately; the fund deducts it quietly from its own assets, so it shows up as a small, continuous drag on returns rather than a line on a statement.
Small differences compound into large ones. Over decades, a fund charging 0.05% versus one charging 0.75% on the same underlying index can leave an investor with a materially larger balance, purely because less was skimmed off each year. For broad, passive index exposure, the expense ratio is often the single most controllable factor in long-run net returns.
A low expense ratio is not automatically the right choice in every case: an actively managed or specialist fund may justify a higher fee if it genuinely delivers something a cheap tracker cannot. But the burden of proof sits with the higher fee, and for mainstream index exposure the cheapest reputable option usually wins.
Worked example
An S&P 500 ETF with a 0.03% expense ratio costs about $3 a year per $10,000 invested; an actively managed fund at 0.80% costs $80 for the same amount.
This definition is general education, not investment advice. Markets — especially crypto — are volatile and you can lose money. Please read our disclaimer and see our methodology.
Related terms
Frequently asked questions
What does Expense ratio mean?
The annual fee a fund charges as a percentage of the money invested, deducted quietly from returns. For index funds it is often the biggest controllable cost.
Is Expense ratio a crypto or a stock-market term?
It is primarily an equities and stock-market term.
Is this Expense ratio definition financial advice?
No. The Market Capitalize glossary is educational — it explains terms and concepts, never a recommendation to buy or sell. See our disclaimer.