What a low-cost index fund is

A low-cost index fund is a fund that tracks a market index — like the S&P 500 or the total U.S. stock market — and charges you a small annual fee to do it. The fund holds the same stocks or bonds as the index it follows, so your returns move with that index. The "low-cost" part means the annual fee, called an expense ratio, is smaller than what most actively managed funds charge.

Expense ratios are expressed as a percentage of the money you have invested. A fund with a 0.03% expense ratio costs you $3 per year for every $10,000 you have in it. A fund with a 0.50% expense ratio costs you $50 per year on the same $10,000. Over decades, that difference compounds — the money you save on fees stays in your account and grows.

Low-cost index funds exist because they do not require a team of analysts trying to beat the market. They straightforward buy and hold the stocks in their index. That simplicity is what keeps the cost down.

Key Takeaways

  • Low-cost index funds track a market index and charge annual fees (expense ratios) typically between 0.03% and 0.20%, compared to 0.50% to 2.00% or higher for actively managed funds.
  • The expense ratio is deducted from your fund's value each year, so a smaller percentage saves you thousands of dollars over a 30-year retirement.
  • You own a piece of every stock or bond in the index, so your returns match the index's performance minus the fee.
  • Low-cost index funds are available through most brokerages, retirement accounts (401(k)s, IRAs), and robo-advisors.
  • The difference between a 0.05% fund and a 0.50% fund can mean tens of thousands of dollars in extra growth by retirement, assuming the same starting balance and time horizon.

How expense ratios affect your money over time

The expense ratio is the single largest cost you pay as a fund investor, and it works against you every year. If your fund grows 7% in a year but charges a 0.50% expense ratio, you keep 6.50% of that growth. The 0.50% comes out before you see your return.

Over 30 years, this matters enormously. Imagine you invest $100,000 in two index funds that both track the same index and earn the same 7% annual return before fees. One charges 0.05% per year; the other charges 0.50% per year. After 30 years, the low-cost fund will have grown to roughly $761,000. The higher-cost fund will have grown to roughly $660,000 — a difference of about $101,000. You did not earn less; you straightforward paid more in fees.

This effect is called fee drag, and it is invisible because you never write a check. The fee is subtracted from your fund's value automatically. But the math is real, and it compounds in reverse — the fees you pay today prevent future growth on that money.

Where to find low-cost index funds

Most major brokerages offer low-cost index funds. Vanguard, Fidelity, and Charles Schwab all have index funds with expense ratios below 0.10%. You can buy them through a regular brokerage account, a 401(k) at work, or an IRA. Some employer retirement plans offer index fund options; others do not.

If your 401(k) plan does not offer low-cost index funds, you can still invest in them through an IRA or a taxable brokerage account. Robo-advisors — automated investment services like Betterment, Wealthfront, and Vanguard Personal Advisor Services — also build portfolios around low-cost index funds, though they charge their own advisory fee on top of the fund's expense ratio.

When you are choosing between funds at your brokerage, look at the expense ratio in the fund's prospectus or fact sheet. It is always listed there. Compare it to other funds tracking the same index; the difference is usually small, but it adds up.

Low-cost index funds versus actively managed funds

An actively managed fund employs a manager or team to pick stocks they believe will outperform the market. That research and trading costs money, which is why actively managed funds typically charge 0.50% to 2.00% or more per year. The fund has to earn enough extra return to cover those fees and still beat the index.

Most actively managed funds do not beat their index over long periods. Studies consistently show that after fees, the average actively managed fund underperforms a low-cost index fund tracking the same market. Some managers do beat the index in a given year, but identifying which ones will do so in the future is difficult. By the time you know a manager has beaten the index, they may have already moved on or their strategy may have changed.

Low-cost index funds do not try to beat the market. They aim to match it, minus the small fee. That is a realistic goal, and it is why they have become the default choice for many retirement savers.

Types of low-cost index funds you might encounter

Index funds come in different varieties, each tracking a different market or part of a market. A total stock market index fund holds thousands of U.S. stocks of all sizes. An S&P 500 index fund holds the 500 largest U.S. companies. An international index fund holds stocks from developed or emerging markets outside the U.S. A bond index fund holds government or corporate bonds.

Each type has its own expense ratio, and low-cost versions exist for all of them. A total stock market index fund might charge 0.03% to 0.04%. An international stock index fund might charge 0.08% to 0.12%. A bond index fund might charge 0.03% to 0.05%. The exact rate depends on the fund provider and how difficult it is to track that particular index.

You do not have to choose just one. Many people hold a mix of index funds — some tracking U.S. stocks, some tracking international stocks, some tracking bonds — to spread risk across different markets. Each fund in the mix will have its own low expense ratio.

What to look for when comparing low-cost index funds

Start with the expense ratio. If two funds track the same index, the one with the lower expense ratio is the better choice, all else equal. The difference between 0.03% and 0.10% may seem tiny, but over 30 years it compounds.

Check the fund's tracking error, which measures how closely the fund's returns match its index. A fund with low tracking error is doing its job well. You can find this information in the fund's prospectus or on the fund provider's website. Most low-cost index funds have very small tracking errors — often less than 0.05% per year.

Also consider the fund's size and age. Larger, older funds tend to be more stable and have lower expense ratios because their costs are spread across more investors. A fund that has been around for 20 years and holds billions of dollars is likely to be more reliable than a brand-new fund with a small balance.

Tax efficiency and low-cost index funds

Index funds are generally more tax-efficient than actively managed funds because they trade less frequently. When a fund buys and sells stocks, it can trigger capital gains taxes in taxable accounts. Index funds hold their stocks for longer periods, so they generate fewer taxable events.

This tax efficiency is an additional benefit on top of the low expense ratio. In a taxable brokerage account, you will owe taxes on any gains you sell or any dividends the fund distributes. In a tax-advantaged account like a 401(k) or IRA, you do not pay taxes until you withdraw the money, so the tax efficiency of the fund matters less.

Some index fund providers have designed their funds to be even more tax-efficient by using techniques like tax-loss harvesting or holding stocks in a way that minimizes distributions. These refinements are most valuable in taxable accounts.

Frequently Asked Questions

What is a good expense ratio for an index fund?

Expense ratios below 0.20% are generally considered low-cost. For a total stock market or S&P 500 index fund, you can find options below 0.05%. For bond or international index funds, 0.10% to 0.15% is typical for low-cost versions. Anything above 0.50% is on the higher end, even for index funds.

Can I lose money in a low-cost index fund?

Yes. The low cost of the fund does not protect you from market losses. If the index the fund tracks goes down, your fund goes down too. The low expense ratio just means you keep more of whatever return the market delivers — whether that return is positive or negative.

Do I need to pick individual index funds or can I buy a fund of funds?

You can do either. Some people buy individual index funds and mix them themselves (for example, 60% U.S. stock index, 30% international stock index, 10% bond index). Others buy a single fund that already holds a mix of index funds — sometimes called a target-date fund or balanced index fund. Both approaches work; the mixed fund is simpler but may have a slightly higher expense ratio.

Are all index funds at the same brokerage the same price?

No. Different brokerages offer their own index funds, and the expense ratios can vary. Vanguard's S&P 500 index fund may charge 0.03%, while another provider's version might charge 0.08%. Always compare the expense ratio across providers before you invest.

What happens to my money if the index fund company goes out of business?

Your money is protected. Index funds are held in your name, separate from the fund company's assets. If the company closes, your shares are transferred to another fund provider. You do not lose your investment because of a company failure.