What makes one index fund better than another for you

The "best" index fund depends on what you're saving for, how long you have until you need the money, and how much you want to pay in fees. Two index funds tracking the same index—say, the S&P 500—can have very different costs. One might charge 0.03% per year while another charges 0.20%. Over decades, that difference compounds into thousands of dollars in your pocket instead of the fund company's.

Beyond fees, the choice comes down to which index you want to own a piece of. An index fund that tracks the S&P 500 gives you 500 large U.S. companies. One that tracks the total U.S. stock market gives you roughly 3,500 companies of all sizes. One that tracks international stocks gives you exposure outside the U.S. The index you choose shapes your risk and potential returns far more than picking between two funds that track the same index.

Key Takeaways

  • Index funds with the lowest expense ratios—often 0.03% to 0.10% per year—cost significantly less over time than funds charging 0.50% or more.
  • The S&P 500 index fund is a common starting point for beginners because it holds 500 large, established U.S. companies and spreads risk across many sectors.
  • Total stock market index funds hold thousands of companies across all sizes and geographies, offering broader diversification than single-index funds.
  • Your choice between funds should reflect your time horizon: aggressive growth funds for decades-away goals, more conservative funds for money you'll need soon.
  • The same index is offered by many providers (Vanguard, Fidelity, Schwab, iShares), so compare fees and account minimums rather than assuming one brand is inherently better.

Low-cost S&P 500 index funds for broad U.S. exposure

The S&P 500 index fund is the most popular choice for people building long-term wealth. It holds 500 of the largest U.S. companies—Apple, Microsoft, Coca-Cola, JPMorgan Chase, and hundreds of others. Because these are established, profitable companies, the index is less volatile than smaller-company funds, though it still moves with the overall market.

The lowest-cost S&P 500 funds charge between 0.03% and 0.04% per year. Vanguard's Vanguard S&P 500 ETF (VOO) and Fidelity's Fidelity 500 Index Fund (FXAIX) both charge 0.03%. Schwab's Schwab U.S. Large-Cap ETF (SCHX) charges 0.03%. These three are functionally identical in cost and holdings—your choice between them depends on which brokerage you already use or prefer. If you're starting fresh, any of these three will serve you well.

An S&P 500 fund works best if you're comfortable with the risk that comes with owning U.S. stocks and don't mind that you're leaving out smaller companies and international markets. For someone with 20+ years until retirement, this is often enough. For someone closer to needing the money, or someone who wants geographic diversification, a broader fund may fit better.

Total stock market index funds for maximum U.S. diversification

A total U.S. stock market index fund holds not just the 500 largest companies but roughly 3,500 companies of all sizes—large, mid-sized, and small. This includes the S&P 500 companies plus thousands of smaller firms. The trade-off is that smaller companies are more volatile, so the fund's price swings more than an S&P 500 fund.

The most common total market funds are Vanguard Total Stock Market ETF (VTI) at 0.03%, Fidelity Total U.S. Stock Market Index Fund (FSKAX) at 0.015%, and Schwab U.S. Total Stock Market ETF (SWTSX) at 0.03%. Fidelity's version is the cheapest, though the difference between 0.015% and 0.03% is small enough that it shouldn't be your only deciding factor.

Total market funds are popular with people who want to own "the whole U.S." without picking and choosing. If you're unsure whether to focus on large companies or include smaller ones, a total market fund removes that decision. Many financial advisors recommend this as a core holding because it's straightforward, cheap, and captures the entire U.S. stock market in one fund.

International index funds for exposure outside the U.S.

An international index fund holds stocks from companies outside the United States—Europe, Asia, emerging markets, and developed markets worldwide. These funds let you own a piece of companies like Nestlé (Switzerland), ASML (Netherlands), or Samsung (South Korea).

Common international funds include Vanguard FTSE Developed Markets ETF (VEA) at 0.05%, which focuses on wealthy countries, and Vanguard FTSE Emerging Markets ETF (VWO) at 0.08%, which focuses on faster-growing economies. Fidelity and Schwab offer similar funds at comparable costs. International stocks can move differently than U.S. stocks, which can reduce overall portfolio risk—but they also add currency risk, since the value of foreign stocks depends partly on exchange rates.

Many people start with U.S. funds and add international exposure later, or use a "three-fund portfolio" combining a U.S. stock fund, an international fund, and a bond fund. If you're just beginning, a U.S.-only fund is simpler. If you want geographic diversification from the start, adding a small international position (10% to 20% of your stock holdings) is a common approach.

Bond index funds for stability and lower risk

A bond index fund holds loans to governments and corporations instead of stocks. Bonds are less volatile than stocks—they don't swing as wildly in price—but they also return less over long periods. A bond fund is useful if you need money within a few years, or if you want to reduce the overall risk in a portfolio that's mostly stocks.

The most popular bond index fund is the Bloomberg U.S. Aggregate Bond Index, tracked by funds like Vanguard Total Bond Market ETF (BND) at 0.03% and Fidelity U.S. Bond Index Fund (FBNDX) at 0.025%. These hold a mix of government bonds, corporate bonds, and mortgage-backed securities. They're stable and predictable, though they return less than stock funds over time.

If you're decades away from needing money, a pure stock portfolio may make sense. If you're within 10 years of a major goal—like retirement or a home purchase—adding bonds reduces the risk that a stock market crash will force you to sell at a loss. A common rule of thumb is to hold your age in bonds and the rest in stocks, though this varies by person and situation.

Target-date funds as an all-in-one alternative

A target-date fund is an index fund that automatically adjusts its mix of stocks and bonds as you get closer to a specific year. A "2050 target-date fund" starts aggressive (mostly stocks) and gradually becomes more conservative (more bonds) as 2050 approaches. This removes the need to decide how much stock versus bond exposure you want.

Vanguard, Fidelity, and Schwab all offer target-date funds with low fees (typically 0.08% to 0.15% per year). You pick the fund that matches when you'll need the money—if you're retiring around 2050, you pick the 2050 fund. The fund company handles the rebalancing automatically.

Target-date funds are popular in retirement accounts like 401(k)s because they're straightforward: you pick one fund and forget about it. The downside is that you have less control over your exact mix of stocks, bonds, and geographies. If you want to customize your portfolio, separate index funds give you more flexibility. If you want simplicity, a target-date fund does the work for you.

How to compare index funds side by side

When you're choosing between two index funds that track the same index, focus on three things: the expense ratio (the annual fee, shown as a percentage), the account minimum (the smallest amount you can invest), and whether the fund is an ETF or a mutual fund.

Expense ratios are the easiest to compare. If Fund A charges 0.03% and Fund B charges 0.20%, Fund A will cost you significantly less over time. On a $10,000 investment over 30 years, that 0.17% difference could mean hundreds of dollars in extra fees.

Account minimums vary. Some index funds have no minimum, while others require $1,000 or $3,000 to start. ETFs (exchange-traded funds) can be bought one share at a time, so they have no minimum beyond the price of a single share. Mutual funds often have minimums, though many brokerages waive them if you set up automatic monthly deposits.

ETFs and mutual funds that track the same index perform nearly identically. The main difference is how you buy them: ETFs trade like stocks throughout the day, while mutual funds are priced once per day after the market closes. For most people starting out, this difference doesn't matter. Pick whichever your brokerage makes easiest to buy.

Frequently Asked Questions

Is an S&P 500 fund or a total market fund better?

Neither is objectively better—it depends on your preference. An S&P 500 fund focuses on 500 large companies and is less volatile. A total market fund includes thousands of smaller companies and is more volatile but captures more of the U.S. economy. Both are low-cost and widely recommended. If you're unsure, a total market fund removes the decision of whether to include smaller companies.

Should I pick Vanguard, Fidelity, or Schwab?

All three offer index funds with nearly identical fees and holdings. Your choice should depend on which brokerage you already use, which has the best user interface for you, or which offers the best customer service. The difference between their index funds is negligible—the bigger factor is your own comfort with the platform.

Can I lose money in an index fund?

Yes. Index funds own stocks or bonds, and both can fall in value. If you invest $10,000 and the market drops 20%, your fund is worth $8,000. However, if you don't sell during the downturn and hold for decades, history shows that stock markets have recovered and grown. The longer your time horizon, the more you can weather short-term losses.

What's the difference between an index fund and an ETF?

An ETF (exchange-traded fund) is a type of index fund that trades like a stock throughout the day. A mutual fund is another type of index fund that's priced once per day after the market closes. Both can track the same index and have the same holdings. ETFs often have lower minimums and are easier to buy in small amounts, but the performance difference is negligible.

Do I need to own international stocks?

No, but many advisors recommend it for diversification. International stocks move differently than U.S. stocks, which can reduce overall portfolio risk. A common approach is to hold 10% to 30% of your stock portfolio in international funds and the rest in U.S. funds. If you're just starting out, a U.S.-only fund is simpler and still builds long-term wealth.