Wall Street has spent decades convincing ordinary people that investing is complicated — that you need a financial advisor, a Bloomberg terminal, and a subscription to three newsletters before you’re qualified to put money in the market. It’s not true. The best-performing strategy for the vast majority of investors is also the simplest: buy a low-cost index fund, keep buying it on a regular schedule, and don’t touch it for decades.
That’s not a fringe opinion. Warren Buffett has said repeatedly that most investors would be better off in an S&P 500 index fund than picking individual stocks. The SEC’s investor education site backs this up with data showing that the majority of actively managed funds underperform their benchmark index over long periods once you account for fees. You’re not settling for average by choosing an index fund. You’re choosing to beat most professional money managers by default.
Here’s how to pick the right one.
What an Index Fund Actually Is (And Why It Works)
An index fund is a mutual fund or exchange-traded fund (ETF) that’s designed to track a specific market index — a predefined list of stocks or bonds selected by a rules-based methodology. The S&P 500 index, for example, tracks the 500 largest publicly traded U.S. companies by market capitalization. When you buy an S&P 500 index fund, you’re buying a tiny slice of all 500 of those companies in one transaction.
The reason this works comes down to a few compounding advantages. First, diversification. Owning 500 companies instead of five means any single company’s collapse barely dents your portfolio. Enron goes to zero? It’s one-fifth of one percent of the index. That kind of risk cushion is hard to replicate on your own without massive capital.
Second, low costs. Because an index fund just mirrors a list rather than employing a team of analysts to pick winners, its operating expenses are minimal. That brings us to the number you’ll see on every fund comparison: the expense ratio.
The expense ratio is the annual fee the fund charges, expressed as a percentage of your investment. A 0.03% expense ratio means you pay $3 per year for every $10,000 invested. A 1.00% expense ratio means you pay $100 for that same $10,000. That difference sounds trivial, but it compounds ruthlessly over time. On a $10,000 investment earning 8% annually over 30 years, a 0.03% expense ratio leaves you with roughly $99,700. A 1.00% expense ratio leaves you with about $76,100. That’s a $23,600 gap on a single $10,000 investment, and it’s entirely attributable to fees. FINRA’s Fund Analyzer tool lets you run these comparisons yourself with real fund data.
Third, tax efficiency. Index funds trade infrequently because the underlying index doesn’t change much from year to year. Lower turnover means fewer taxable events, which means you keep more of your gains in a taxable brokerage account.
S&P 500, Total Market, or International: Picking Your Index
The best index funds for beginners generally fall into three categories, and understanding the differences will tell you which one (or which combination) makes sense for you.
S&P 500 index funds are the most popular starting point, and for good reason. The S&P 500 has returned roughly 10% per year on average since its inception, including dividends. It gives you exposure to the largest, most established American companies — Apple, Microsoft, JPMorgan, UnitedHealth, and so on. The biggest names in this space are Vanguard’s VOO (expense ratio: 0.03%), Fidelity’s FXAIX (0.015%), and Schwab’s SWPPX (0.02%). You can’t go wrong with any of them. The performance differences are negligible because they’re all tracking the same index.
Total U.S. stock market funds go a step further by including not just the 500 largest companies but the entire investable U.S. stock market — roughly 3,600 to 4,000 stocks, depending on the fund. This adds small-cap and mid-cap companies that aren’t in the S&P 500. Historically, small-cap stocks have delivered slightly higher returns over very long periods, though with more volatility. Vanguard’s VTI (0.03%) and Fidelity’s FSKAX (0.015%) are the heavyweights here. In practice, about 80% of a total market fund overlaps with the S&P 500 because the largest companies dominate by market weight. If you can only own one fund, a total market fund gives you slightly broader coverage.
International index funds track stocks outside the United States. The logic for including them is straightforward: the U.S. represents roughly 60% of global stock market capitalization, which means 40% of the world’s investable companies are elsewhere. International diversification protects you against prolonged periods where U.S. stocks underperform — and those periods exist. From 2000 to 2009, the S&P 500 returned essentially nothing while international developed markets did substantially better. Vanguard’s VXUS (0.07%) and Fidelity’s FTIHX (0.06%) cover developed and emerging markets outside the U.S. A common allocation for a young investor is 60-70% U.S. and 30-40% international, though there’s no magic number.
The SEC’s introduction to mutual funds and ETFs provides a solid primer on how these vehicles are structured and regulated if you want the foundational details.
How to Choose: Brokerage, Account Type, and Getting Started
Picking the fund is half the equation. The other half is where and how you buy it, because the brokerage you use and the account type you open can meaningfully affect your returns.
Choose a brokerage that offers commission-free trading and no account minimums. Fidelity, Schwab, and Vanguard are the three dominant platforms for index fund investors. All three now offer $0 commissions on stock and ETF trades, and their proprietary index funds carry some of the lowest expense ratios in the industry. If you already have a 401(k) with one of these providers, it can simplify things to open your taxable brokerage account with the same firm. But don’t overthink this — the difference between brokerages is marginal. What matters is that you pick one and start.
Account type matters for taxes. A Roth IRA lets your investments grow tax-free and come out tax-free in retirement. A traditional IRA gives you a tax deduction now and taxes you later. A taxable brokerage account offers no tax advantages but gives you full flexibility to withdraw money anytime. For most beginners, maxing out a Roth IRA first (the 2026 contribution limit is $7,000 if you’re under 50) and then investing additional money in a taxable account is the optimal sequence. FINRA’s account comparison resources explain the tradeoffs in detail.
How much do you need to start? Less than you think. Many ETFs trade for under $100 per share, and most brokerages now support fractional shares, meaning you can buy $25 worth of a $500 ETF. Fidelity’s index mutual funds have zero minimums. The idea that you need $5,000 or $10,000 to start investing is outdated. If you have $50, you can open a brokerage account and buy fractional shares of a total market ETF today. The amount doesn’t matter nearly as much as the habit.
Set up automatic investing. The single most effective thing you can do as a beginner investor is automate the process. Set up a recurring transfer from your checking account to your brokerage account on payday, and set up automatic purchases of your chosen index fund. This accomplishes two things: it removes the emotional component from investing (you buy regardless of whether the market is up or down), and it implements dollar-cost averaging, which smooths out your purchase price over time.
Mistakes That Cost Beginners Real Money
Knowing the right strategy is necessary but not sufficient. You also need to avoid the behavioral traps that derail beginners every year.
Trying to time the market. You’ll hear about some guru who called the 2020 crash or predicted the 2025 rally. What you won’t hear is the dozen times they were wrong. Study after study, including research compiled by the SEC, shows that time in the market beats timing the market. Missing just the ten best trading days over a 20-year period can cut your returns in half. Those best days often come right after the worst days, so if you panicked and sold during a crash, you missed the recovery.
Checking your portfolio too often. Daily price movements are noise. Weekly movements are mostly noise. Monthly movements are still largely noise. The signal — the thing that actually matters — only emerges over years and decades. Checking your account daily doesn’t make you a more informed investor. It makes you an anxious one who’s more likely to sell at the wrong time. Set it up, automate it, and check quarterly at most.
Not diversifying enough. Owning a single S&P 500 fund is already well-diversified by individual stock standards, but you’re still 100% in U.S. large-cap equities. Adding a total international fund, and eventually some bond exposure as you age, reduces your portfolio’s volatility without meaningfully sacrificing returns. A simple three-fund portfolio — U.S. total market, international total market, and U.S. bond index — has been the backbone of sensible retirement portfolios for decades.
Chasing performance. Last year’s best-performing fund is almost never this year’s best-performing fund. Pouring money into whatever sector just had a great quarter is a reliable way to buy high and sell low. Index funds solve this problem by design: you own the whole market, so you’re always holding the winners, even before you know who they are.
Ignoring tax-advantaged accounts. If your employer offers a 401(k) match, contribute enough to get the full match before investing anywhere else. It’s a guaranteed 50% or 100% return on your money depending on the match formula. After that, fund a Roth IRA. Only after those accounts are maxed should you invest in a taxable brokerage account for long-term goals.
Paying for advice you don’t need yet. Financial advisors serve an important role for people with complex situations — estate planning, business ownership, concentrated stock positions. But if you’re 28 and investing $500 a month into an index fund, you don’t need to pay someone 1% of your assets annually to tell you to keep doing that. At this stage of your investing life, a target-date retirement fund or a simple two- or three-fund portfolio does the job. Save the advisory fees for when your financial life actually gets complicated.
The best index funds for beginners aren’t the ones with the cleverest marketing or the flashiest returns last quarter. They’re the ones with rock-bottom expense ratios, broad market exposure, and a track record measured in decades. Pick one, automate your contributions, resist the urge to tinker, and let compound interest do what it does best. That’s the whole strategy. It’s simple, it’s boring, and it works better than almost everything else.
Frequently Asked Questions
What is the best index fund for beginners to start with?
A total U.S. stock market fund like Vanguard’s VTI (0.03% expense ratio) or Fidelity’s FSKAX (0.015%) is the most common recommendation for beginners. It gives you exposure to roughly 3,600 to 4,000 U.S. stocks in a single purchase, including large, mid, and small companies. If you’d rather stick with the 500 largest companies, an S&P 500 fund like VOO or FXAIX works just as well.
How much money do you need to start investing in index funds?
Less than you’d think. Most brokerages now support fractional shares, so you can invest as little as $1 or $5 into an ETF. Fidelity’s index mutual funds have zero minimum investment requirements. The idea that you need thousands of dollars to start is outdated. What matters more than the starting amount is building a consistent habit of investing regularly.
What's the difference between an index fund and an ETF?
An index fund is the strategy (tracking a market index like the S&P 500), and it can be structured as either a mutual fund or an ETF. Mutual fund versions trade once per day after the market closes, while ETFs trade throughout the day like stocks. For long-term buy-and-hold investors, the difference is minimal. ETFs sometimes have slight tax advantages in taxable accounts, and mutual funds are easier to set up with automatic recurring purchases.
Do index funds pay dividends?
Yes. Most stock index funds pay dividends, typically quarterly, based on the dividends paid by the underlying companies in the index. For an S&P 500 fund, the dividend yield is usually around 1.3% to 1.8% annually. You can choose to receive dividends as cash or reinvest them automatically to buy more shares, which is what most long-term investors do to maximize compounding.
Are index funds better than picking individual stocks?
For the vast majority of investors, yes. Data consistently shows that most actively managed funds and individual stock pickers underperform a simple index fund over long periods once fees are factored in. Even Warren Buffett has said most people would be better off in a low-cost S&P 500 index fund. You’re not settling for mediocre returns, you’re choosing to beat most professional money managers by default.