If you've ever asked a financial advisor, a coworker, or even a finance-savvy friend how to start investing, chances are you've heard the same answer: "Just buy an S&P 500 index fund." It's simple, low-cost advice that has helped millions of everyday investors build long-term wealth without needing to pick individual stocks.
But here's the catch nobody mentions upfront: there isn't just one S&P 500 fund. There are dozens of exchange-traded funds (ETFs) that all track the same 500 U.S. companies, yet they differ in fees, size, liquidity, and structure. Choosing the "wrong" one won't ruin your financial future, but choosing the right one can quietly save you thousands of dollars over a lifetime of investing.
This guide breaks down the most popular S&P 500 ETFs in plain language, with real numbers, a couple of everyday examples, and a clear framework for deciding which one fits your situation.
👍What Is an S&P 500 ETF, Exactly?
The S&P 500 is an index of roughly 500 of the largest publicly traded companies in the United States, spanning technology, healthcare, finance, consumer goods, and more. An S&P 500 ETF is simply a fund that buys those same 500 companies in the same proportions, so when you buy one share, you effectively own a tiny slice of all 500 businesses at once.
Because these funds are "passively managed" (nobody is picking stocks; the fund just mirrors the index), their operating costs are extremely low compared to actively managed mutual funds. That low cost is a big part of why index investing has become the default recommendation for long-term investors.
👇Meet the Main Contenders
Four funds dominate this space: SPY, VOO, IVV, and SPLG. A fifth, RSP, tracks the same 500 companies but weights them equally instead of by size, giving it a different risk profile worth knowing about.
| ETF Ticker | Fund Name | Issuer | Inception Date | Expense Ratio | Approx. AUM (2026) |
|---|---|---|---|---|---|
| SPY | SPDR S&P 500 ETF Trust | State Street | January 1993 | 0.0945% | ~$641.5 billion |
| VOO | Vanguard S&P 500 ETF | Vanguard | September 2010 | 0.03% | ~$1.03 trillion |
| IVV | iShares Core S&P 500 ETF | BlackRock | May 2000 | 0.03% | ~$833 billion |
| SPLG | SPDR Portfolio S&P 500 ETF | State Street | November 2005 | 0.02% | ~$97.3 billion |
| RSP | Invesco S&P 500 Equal Weight ETF | Invesco | April 2003 | 0.20% | Smaller, niche fund |
At first glance, these numbers might look almost identical. An expense ratio of 0.03% versus 0.10% sounds like nothing. But small percentages compound in big ways over long periods, which is exactly why it's worth understanding the differences before you invest.
👇Expense Ratios and Fund Size at a Glance
The chart below shows how the four core funds stack up on cost and scale.
👉Why Does SPY Cost More?
SPY isn't more expensive because it's poorly run. It's expensive because of its legal structure. SPY was launched in 1993 as a Unit Investment Trust (UIT), one of the very first ETFs ever created. That structure legally prevents the fund from lending out its shares or reinvesting dividends the same flexible way that newer, open-end funds like VOO and IVV can. In short, SPY is a bit like a vintage car: reliable, iconic, and still highly functional, but built with older technology that costs more to run.
VOO and IVV, launched years later as open-end funds, don't have that limitation, which is a major reason their expense ratios can sit at a rock-bottom 0.03%.
👉A Real-World Example: Two Coworkers, Two Choices
Let's put this into a story that's easy to relate to.
David Thompson and Rachel Martinez both work at the same marketing firm in Austin, Texas, and both decided to start investing $10,000 in an S&P 500 ETF at age 30, planning to hold it for 30 years until retirement. Neither of them touches the account after the initial investment — no additional deposits, no withdrawals, just a long, patient hold.
David, who had heard of SPY from a news article about the stock market, bought SPY. Rachel, after reading a short comparison online, chose VOO instead. Assuming both funds return a hypothetical 8% per year before fees, here's how the fee difference alone plays out over three decades:
| Investor | Fund | Expense Ratio | Value After 30 Years (on $10,000) |
|---|---|---|---|
| David Thompson | SPY | 0.0945% | ≈ $98,018 |
| Rachel Martinez | VOO | 0.03% | ≈ $99,791 |
The gap — about $1,773 on a $10,000 investment — might not sound life-changing. But scale that up to a $100,000 nest egg, and the difference grows to roughly $17,730, as shown in the chart below. That's a family vacation, a semester of community college, or a solid head start on a grandchild's savings account, generated purely by picking a lower-cost fund and doing absolutely nothing else differently.
To be fair to David, his choice wasn't a mistake — it simply came with a trade-off he didn't need. SPY's advantage isn't cost efficiency; it's liquidity. SPY trades tens of millions of shares a day with razor-thin bid-ask spreads, which matters enormously to institutional traders and options investors, but rarely matters to someone who buys once and holds for decades.
👉When Liquidity Actually Matters
Consider a second example: Michael Chen, a self-employed options trader in Chicago, regularly buys and sells S&P 500 options contracts as part of his short-term trading strategy. For Michael, SPY's deep options market and enormous daily trading volume aren't a luxury — they're essential to getting a fair price every time he places a trade. In his case, paying the higher 0.0945% expense ratio is a reasonable price for the liquidity and flexibility SPY provides.
This is the key lesson: the "best" S&P 500 ETF depends entirely on how you plan to use it.
👇Choosing Between VOO, IVV, and SPLG
If you've settled on a low-cost, buy-and-hold approach, the real decision comes down to VOO, IVV, or SPLG, since all three charge nearly identical rock-bottom fees. The differences here are much smaller and largely come down to personal preference:
| Factor | VOO | IVV | SPLG |
|---|---|---|---|
| Expense Ratio | 0.03% | 0.03% | 0.02% (lowest) |
| Fund Size (AUM) | Largest (~$1.03T) | Large (~$833B) | Smallest of the three (~$97B) |
| Share Price | Higher | Higher | Lower (easier for small accounts without fractional shares) |
| Issuer | Vanguard | BlackRock (iShares) | State Street |
| Best For | Long-term investors who want the largest, most established fund | Investors already using BlackRock/iShares platforms | Beginners and small accounts wanting the lowest possible cost |
Jennifer Walsh, a 24-year-old teacher in Ohio just starting her investing journey with $500 a month, is a good example of who benefits most from SPLG. Because SPLG's share price tends to run lower than VOO's or SPY's, and its expense ratio is the lowest of the group, it's an appealing option for someone building a position gradually, especially at brokerages that don't support fractional-share purchases.
👍What About Mutual Funds Like FXAIX?
If you're investing through a 401(k) retirement account rather than a personal brokerage account, you may not even have the option to buy an ETF. Many employer retirement plans instead offer S&P 500 index mutual funds, such as Fidelity's FXAIX, which carries an even lower expense ratio around 0.015%. Inside a tax-advantaged account like a 401(k), the tax-efficiency advantages that ETFs normally offer over mutual funds don't really apply, so FXAIX or a similar low-cost index mutual fund is often a perfectly good — even ideal — choice in that context.
⭐A Simple Decision Framework
To simplify everything above, here's a straightforward way to think about it:
- You're a long-term, buy-and-hold investor and want the simplest, most established option → VOO or IVV
- You're just starting out with small, regular contributions → SPLG
- You actively trade or use options strategies → SPY
- You're investing inside a 401(k) with a mutual fund option → FXAIX or your plan's equivalent
- You want to reduce concentration in mega-cap tech stocks → Consider RSP (equal-weight), understanding it carries a higher fee and different risk/return pattern
💢Summary
All of the funds discussed here — SPY, VOO, IVV, and SPLG — track the exact same 500 companies and will move up and down together almost identically day to day. The real differences lie in cost, liquidity, share price, and fund structure, not in what you actually own.
- SPY is the oldest and most heavily traded, ideal for active traders and options investors, but carries the highest expense ratio (0.0945%) due to its legacy trust structure.
- VOO and IVV are nearly identical, ultra-low-cost (0.03%) funds best suited for long-term, buy-and-hold investors.
- SPLG offers the lowest expense ratio (0.02%) and a lower share price, making it especially attractive for beginners and small accounts.
- FXAIX and similar mutual funds are strong choices inside employer-sponsored retirement accounts.
For most everyday investors — people like Rachel or Jennifer — the fee difference between these funds, while small in percentage terms, adds up meaningfully over decades. The good news is that you genuinely cannot make a "bad" choice among VOO, IVV, or SPLG; any of them will serve a patient, long-term investor well. What matters far more than which ticker you choose is starting early, contributing consistently, and staying invested through market ups and downs.
※Sources and References
- TrendSpider, "SPY vs VOO vs IVV: Which S&P 500 ETF Is Actually Better in 2026?" — trendspider.com
- Dr Wealth, "SPY vs VOO vs IVV ETFs: Which Is the Best S&P 500 ETF?" — drwealth.com
- Mezzi, "SPLG vs VOO vs IVV: Cheapest S&P 500 ETF for Small Accounts" — mezzi.com
- Westmount Fundamentals, "ETF Expense Ratios 2026: 86 ETFs Ranked + Average by Category" — westmountfundamentals.com
- 8Figures, "Best S&P 500 Index Funds for 2026: VOO vs SPY vs IVV Compared" — 8figures.com
- MyInvestAcademy, "Best S&P 500 ETFs in 2026: VOO vs SPY vs IVV Compared" — myinvestacademy.com
- EigenDex Blog, "7 Best S&P 500 ETFs in 2026: VOO, SPY, IVV & More Compared" — eigendex.com
- InvestSnips, "Best S&P 500 ETFs: Top 10 Picks for 2026 Compared" — investsnips.com
- DividendVision, "IVV vs SPLG vs SPY vs VOO: Side-by-Side ETF Comparison 2026" — dividendvision.com
💣Note: Expense ratios, AUM figures, and share prices cited above reflect data reported in early-to-mid 2026 across the sources listed and may change over time. Growth projections in this article are hypothetical illustrations assuming a constant 8% gross annual return and are not guarantees of future performance.
This article is for educational purposes only and does not constitute personalized financial advice. Consult a licensed financial advisor before making investment decisions.
