The S&P 500 is not itself an index fund — it's the benchmark that index funds track

The S&P 500 is a list of 500 large U.S. companies, ranked by market value. It's a measuring stick. An index fund is an investment product you can buy into that holds those same 500 stocks in the same proportions, so your returns match the S&P 500's performance.

Think of it this way: the S&P 500 is like a recipe. An S&P 500 index fund is like a restaurant that cooks that recipe and serves it to you. You can't buy the S&P 500 directly — you buy a fund that mirrors it.

The confusion happens because people use "S&P 500" and "S&P 500 index fund" interchangeably in conversation, but they're different things. When you hear someone say "I'm investing in the S&P 500," they almost always mean they're buying shares of an S&P 500 index fund.

Key Takeaways

  • The S&P 500 is a list of 500 companies used as a market benchmark; an S&P 500 index fund is an investment product that holds those stocks.
  • You cannot buy the S&P 500 directly — you buy an index fund that tracks it, such as those offered by Vanguard, Fidelity, or Schwab.
  • Different S&P 500 index funds charge different fees, so comparing expense ratios between providers matters for your long-term returns.
  • An S&P 500 index fund gives you ownership in 500 companies with a single purchase, spreading your risk across many businesses.

How an S&P 500 index fund actually works

When you buy shares of an S&P 500 index fund, you're buying a slice of a fund that holds all 500 stocks in the index. The fund manager doesn't pick which stocks to buy — they simply hold the same companies in the same weights as the S&P 500 itself. If Apple makes up 7% of the S&P 500, it makes up 7% of the fund.

The fund collects dividends from those 500 companies and either pays them out to you or reinvests them, depending on the fund type. When you sell your shares, you get the current value of your slice of the fund, which rises or falls with the overall market value of those 500 stocks.

This is different from an actively managed fund, where a manager picks individual stocks they think will outperform. An S&P 500 index fund does no picking — it just mirrors the index.

Where you actually buy S&P 500 index funds

You buy S&P 500 index funds through a brokerage account — an online account where you can hold and trade investments. Common brokerages include Fidelity, Vanguard, Charles Schwab, E-Trade, and Robinhood, though many others exist.

You open an account, link a bank account, deposit money, and then search for an S&P 500 index fund by its ticker symbol. Vanguard's version is VOO. Fidelity's is FSKAX. Schwab's is SWPPX. Each one tracks the same 500 companies but may charge slightly different fees.

You can also hold S&P 500 index funds inside retirement accounts like a 401(k) or IRA, where they often appear as investment options your employer or the account provider offers.

Why the fees matter between different S&P 500 index funds

All S&P 500 index funds hold the same stocks, so they should perform almost identically — but they don't, because of fees. The expense ratio is the annual percentage you pay to own the fund. It might be 0.03% per year or 0.20% per year, depending on the provider.

That sounds tiny, but over decades it compounds. On a $10,000 investment, the difference between a 0.03% fee and a 0.20% fee is about $7 per year now, but grows to hundreds of dollars over 30 years because you're not earning returns on that money. Vanguard, Fidelity, and Schwab all offer S&P 500 index funds with expense ratios below 0.10%, which is considered very low.

Before you buy, check the expense ratio of the specific fund. It's listed in the fund's prospectus or on the brokerage website. Lower is better, all else equal.

The difference between an index fund and the index itself

The S&P 500 index is maintained by S&P Global, a financial data company. They decide which 500 companies belong in it and rebalance it periodically. The index itself is just a number — it's calculated and published, but you can't own it.

Index funds are created by investment companies like Vanguard or Fidelity. They build a fund that mimics the index, charge you a fee to manage it, and handle the paperwork of buying and selling the underlying stocks. You own shares of the fund, not the index.

This is why you see the S&P 500 quoted as a number (like "the S&P 500 closed at 5,200 today") but you buy an index fund as a share price (like "VOO closed at $487 today"). One is a benchmark; the other is an investment product.

Why people choose S&P 500 index funds

An S&P 500 index fund gives you ownership in 500 large, established U.S. companies with a single purchase. You're not betting on one company or one industry — you're spreading your money across Apple, Microsoft, Coca-Cola, JPMorgan, Nvidia, and hundreds of others. If one company struggles, the others cushion the blow.

Index funds also charge much less than actively managed funds, where a manager tries to beat the market by picking stocks. Most actively managed funds don't beat the S&P 500 over long periods, so you're paying more for worse results. An S&P 500 index fund simply matches the market, which is what most investors should want.

They're also simple to understand and require no ongoing decisions. You buy it, hold it, and let it grow. You don't have to research individual companies or time the market.

Frequently Asked Questions

Can I lose money in an S&P 500 index fund?

Yes. If the stock market falls, the value of your fund falls with it. The S&P 500 has dropped 20% or more several times in the past 50 years. However, it has always recovered and reached new highs over longer time periods. If you need the money within a few years, an index fund is riskier than keeping cash.

What's the difference between VOO, FSKAX, and SWPPX?

They all track the same 500 companies and perform nearly identically. VOO (Vanguard) charges 0.03% annually, FSKAX (Fidelity) charges 0.015%, and SWPPX (Schwab) charges 0.03%. The differences are tiny, but FSKAX is slightly cheaper. All three are considered excellent choices.

Do I get dividends from an S&P 500 index fund?

Yes, if the fund distributes them. Many of the 500 companies pay dividends. The fund collects those dividends and either pays them to you as cash or automatically reinvests them to buy more shares. Check the fund's details to see which option it uses by default.

Is an S&P 500 index fund the same as a total stock market index fund?

No. An S&P 500 fund holds 500 large companies. A total stock market fund holds thousands of companies of all sizes, including mid-size and small companies. Total market funds are more diversified but perform similarly over long periods because large companies make up most of the market's value.

Can I buy an S&P 500 index fund inside a 401(k)?

Often yes. Many employers' 401(k) plans offer S&P 500 index funds as investment options. Check your plan's investment menu. If your employer offers one, it's usually a good choice because 401(k) contributions reduce your taxable income and may come with employer matching.