Index Funds for Beginners: How to Start Investing (Step-by-Step Guide)
Updated October 2026 · 11 min read
Picking stocks sounds exciting. You research a company, buy its shares, and wait for the price to climb. In reality, most people who try it, including most professional fund managers, end up doing worse than the market as a whole.
There's a simpler path, and it's the one many of the world's most respected investors recommend to ordinary people: index funds. With a single purchase, you can own a small slice of hundreds or even thousands of companies, pay almost nothing in fees, and skip the guesswork of choosing winners.
This guide on index funds for beginners explains what index funds are, why they work, how to pick one, and exactly how to make your first investment.
Key takeaways
- An index fund tracks a market index, such as the S&P 500, instead of trying to beat it.
- In 2025, 79% of actively managed large-cap US stock funds trailed the S&P 500.
- Low fees matter: on a typical 30-year plan, a 0.57% fee can cost about $65,000 more than a 0.03% fee.
- You can start with one broad fund, a brokerage account, and an automatic monthly deposit.
In this guide:
- What is an index fund?
- Why index funds beat most professionals
- The hidden power of low fees
- Types of index funds
- Index ETFs vs. index mutual funds
- How to start investing in index funds
- Simple example portfolios
- 5 beginner mistakes to avoid
- Frequently asked questions
What Is an Index Fund?
An index fund is a mutual fund or exchange-traded fund (ETF) that copies a market index. An index is simply a list of companies chosen by a set of rules. The S&P 500, for example, tracks about 500 of the largest publicly traded companies in the United States.
When you buy an S&P 500 index fund, the fund buys the stocks in that index for you, in roughly the same proportions. If the index goes up 10% in a year, your fund goes up about 10%, minus a tiny fee.
Vanguard founder John Bogle, who launched the first index fund for everyday investors in 1976, summed up the idea in one line: "Don't look for the needle in the haystack. Just buy the haystack." Instead of guessing which company will be the next big winner, you own all of them.
How an Index Fund Works
Most stock indexes are market-cap weighted. That means bigger companies make up a bigger share of the fund. A trillion-dollar tech company gets far more weight than a $20 billion retailer.
Here's what that looks like with a $1,000 investment. If a company makes up 5% of the index, about $50 of your money goes into its shares. A company that makes up 0.05% gets about 50 cents. The fund handles all of this automatically and rebalances when the index changes. You never have to buy or sell individual stocks yourself.
Active Funds vs. Index Funds
An actively managed fund pays a team of analysts to choose stocks they think will beat the market. An index fund doesn't try to beat the market. It simply aims to match it. Because there's no research team to pay and very little trading, index funds cost much less to run.
Why Index Funds Beat Most Professionals
It sounds backwards. How can a fund that doesn't even try to win beat the experts? The answer shows up year after year in the data.
S&P Dow Jones Indices publishes a report called the SPIVA Scorecard, which compares active funds with their benchmarks. In 2025, 79% of actively managed large-cap US stock funds underperformed the S&P 500 (S&P Dow Jones Indices).
The longer the time frame, the worse it gets for active managers. Over the 20 years ending June 2024, only about 8% of large-cap funds beat the S&P 500. Roughly 92% fell behind (The Motley Fool, citing SPIVA data).
There are three main reasons:
- Costs. Active funds charge higher fees, and those fees come out of returns every single year.
- Competition. Professional investors are mostly trading against other professionals. Being smart isn't enough when everyone else is smart too.
- Consistency is rare. A manager who beats the market one year often trails it the next. Spotting the few long-term winners in advance is extremely hard.
When you buy an index fund, you're guaranteed to get the market's return, minus a tiny fee. Over decades, that "average" result has quietly beaten the large majority of experts.
The Hidden Power of Low Fees
Every fund charges an annual fee called the expense ratio, shown as a percentage of your investment. A 0.03% expense ratio means you pay $3 a year for every $10,000 invested.
That sounds like small change, and in any single year it is. But fees compound just like returns do. According to Morningstar's latest fee study, the asset-weighted average expense ratio was 0.57% for active funds and 0.09% for passive funds at the end of 2025 (Morningstar).
Let's see what that difference does over time. Imagine you invest $10,000 today and add $500 every month for 30 years. That's $190,000 of your own money. Assume the investments earn 7% a year before fees:
| Annual fee (expense ratio) | Value after 30 years | Lost to fees vs. 0.03% |
|---|---|---|
| 0.03% (low-cost index fund) | $656,989 | — |
| 0.09% (average passive fund) | $649,343 | $7,646 |
| 0.57% (average active fund) | $591,602 | $65,386 |
| 1.00% (high-cost fund) | $544,691 | $112,297 |
Hypothetical example for illustration. Assumes a constant 7% annual return before fees, compounded monthly, with no taxes. Real returns vary from year to year.
Same deposits, same market, very different results. The 1% fund costs over $112,000, more than half of everything you put in. This is why choosing a low-cost fund is one of the few investing decisions that is completely in your control.
Types of Index Funds
There are index funds for almost every corner of the market. As a beginner, you only need to know a few main types:
| Type | What you own | Best for |
|---|---|---|
| S&P 500 | About 500 large US companies | A simple core holding of big, established firms |
| Total US stock market | Several thousand US companies, large and small | The broadest single bet on the US economy |
| International stocks | Companies in Europe, Asia and emerging markets | Spreading risk beyond one country |
| Bond index | Government and corporate bonds | Steadier value and income, especially near retirement |
| Target-date fund | A mix of stock and bond index funds that gets safer over time | Hands-off retirement investing in one fund |
Popular S&P 500 Index Funds Compared
Several big fund companies offer nearly identical S&P 500 funds. The main differences are the fee and whether the fund is an ETF or a mutual fund:
| Fund (ticker) | Type | Expense ratio | Yearly cost per $10,000 |
|---|---|---|---|
| Fidelity 500 Index Fund (FXAIX) | Mutual fund | 0.015% | $1.50 |
| Schwab S&P 500 Index Fund (SWPPX) | Mutual fund | 0.02% | $2.00 |
| Vanguard S&P 500 ETF (VOO) | ETF | 0.03% | $3.00 |
| SPDR S&P 500 ETF Trust (SPY) | ETF | 0.09% | $9.00 |
Expense ratios change over time. Check the fund company's website for the current figure before you invest.
All four hold the same companies, so their returns are nearly identical. Any of them is a solid choice. The best one is usually the one offered at the brokerage you already use.
Index ETFs vs. Index Mutual Funds
Index funds come in two wrappers. The investments inside are the same, but the way you buy them is a little different:
| Feature | Index ETF | Index mutual fund |
|---|---|---|
| How it trades | Like a stock, all day long | Once a day, at the closing price |
| Minimum to start | One share, or less with fractional shares | Varies; some have $0 minimums, others $1,000 or more |
| Automatic investing | Depends on the broker | Easy to set up in exact dollar amounts |
| Tax efficiency in taxable accounts | Usually very high | Good, though often slightly lower |
| Works at any brokerage | Yes | Often best at the fund's own company |
For most beginners, the choice doesn't matter much. If you want to set up automatic $200 monthly deposits, a mutual fund at your broker's own fund family is often easiest. If you want flexibility to use any brokerage app, an ETF works everywhere.
How to Start Investing in Index Funds
You can go from zero to invested in an afternoon. Here's the process, step by step.
- Cover the basics first. Build an emergency fund of three to six months of expenses and pay off high-interest debt, like credit cards charging 20% or more. No index fund reliably beats a 20% interest rate.
- Pick an account type. If your employer offers a 401(k) with a match, start there, because the match is free money. Next, consider an IRA for tax advantages. A regular brokerage account works for goals outside retirement.
- Open the account. Large brokers like Fidelity, Schwab and Vanguard all offer low-cost index funds and $0 commissions on stock and ETF trades. Opening an account takes about 15 minutes online.
- Choose your fund. One broad fund, like an S&P 500 or total market index fund, is enough to start. Check that the expense ratio is under 0.10%.
- Decide how to invest your money. If you have a lump sum, read our guide on dollar-cost averaging vs. lump sum investing to decide whether to invest it all at once.
- Automate monthly deposits. Set up an automatic transfer and purchase on the same day each month. This turns investing into a habit you don't have to think about.
A Real-World Example
Meet Jordan, 28, who just opened a Roth IRA. Jordan picks a total US stock market index fund with a 0.03% expense ratio and sets up an automatic $300 investment on the 5th of every month.
That's it. There's no stock research and no checking prices every day. If Jordan keeps that habit and the fund earns 7% a year on average, the account would grow to roughly $350,000 by age 58. Jordan would have put in $108,000; the rest is growth. Real returns will be bumpier than that, with some down years along the way, but the plan stays the same.
Simple Example Portfolios
You don't need a complicated portfolio. Many experienced investors use just one to three funds. Here are three common structures, shown as examples rather than recommendations:
| Portfolio | Funds and split | Why people choose it |
|---|---|---|
| One-fund | 100% target-date fund | Fully hands-off; it rebalances and gets safer on its own |
| Two-fund | 80% total US stock, 20% total bond | Simple growth with a cushion for down years |
| Three-fund | 60% total US stock, 20% international stock, 20% total bond | Adds global diversification while staying simple |
The right split depends on your age, goals and comfort with risk. A common rule of thumb: the closer you are to needing the money, the more of it belongs in bonds.
5 Beginner Mistakes to Avoid
- Selling during a crash. Index funds fall when the market falls. Selling after a 25% drop locks in the loss and often means missing the recovery. The strategy only works if you stay invested.
- Ignoring the expense ratio. Two funds with the same name, like "S&P 500 index," can charge very different fees. Some charge 0.50% or more. Always check before you buy.
- Owning too many overlapping funds. An S&P 500 fund, a total market fund and a large-cap growth fund hold many of the same companies. Owning all three adds complexity, not diversification.
- Chasing last year's hot fund. A tech or sector index fund that jumped 40% last year can easily lag next year. Keep broad funds at the core of your portfolio.
- Waiting for the "right time" to start. Nobody can predict short-term market moves reliably. Time in the market matters far more than timing the market.
Frequently Asked Questions
Are index funds safe?
Index funds are diversified, so one company's failure won't sink your investment. But a stock index fund still rises and falls with the market and can lose 30% or more in a bad year. They are best for money you won't need for at least five years.
How much money do I need to start?
Very little. Many brokers offer fractional shares of ETFs, and some index mutual funds have no minimum. You can realistically start with $50 or $100.
Do index funds pay dividends?
Yes. Stock index funds pass along the dividends paid by the companies they own, usually every quarter. Most brokers let you reinvest them automatically, which helps your investment compound faster.
Is an S&P 500 fund diversified enough?
It owns about 500 companies across every major industry, which is far more diversified than picking a few stocks. However, it holds only large US companies. Adding international and bond funds spreads your risk further.
What's the difference between an index fund and an ETF?
"Index fund" describes the strategy: tracking an index. "ETF" describes the structure: a fund that trades like a stock. Many ETFs are index funds, but some ETFs are actively managed, and many index funds are mutual funds.
The Bottom Line
Index funds give you a simple, low-cost way to own the whole market. The data shows that most professional managers fail to beat them over the long run, and every dollar you save on fees stays invested and keeps growing.
Getting started takes three decisions: open an account, pick one broad, low-cost fund, and automate a monthly deposit. After that, your most important job is to leave it alone and let decades of compounding do the work.
Disclaimer: This article is for educational purposes only and is not financial advice. Funds and tickers are mentioned as examples, not recommendations. Past performance does not guarantee future results. Consider your own situation or consult a licensed financial professional before investing.
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