If you have ever wondered what is the S&P 500, you have already found the most important number in US investing. It is the benchmark everyone uses as shorthand for "how is the stock market doing?"
The S&P 500 tracks 500 of the largest publicly traded US companies, from Apple and Microsoft to Coca-Cola and Visa. When people say the market was up or down, they are usually quoting this index.
The good news for beginners is that you do not need to pick winners one by one. A handful of low-cost funds let you own the whole index, and Gotrade makes it accessible with fractional shares from $1.
What the S&P 500 Is and How It's Built
The S&P 500 is a stock market index maintained by S&P Dow Jones Indices. It measures the combined performance of 500 leading US companies and captures roughly 80% of the total value of the US public market, making it a strong proxy for the broader economy.
A common myth is that the index is simply the 500 biggest companies. It is not automatic. A committee selects members, and a company has to clear a real bar before it qualifies.
Eligibility basics
A company must be US-based, listed on a major exchange like the NYSE or Nasdaq, and large enough to meet a market-cap threshold in the tens of billions of dollars. It also needs healthy trading volume so shares change hands easily.
The profitability test
According to Fidelity, a candidate must also show positive earnings over the most recent quarter and the four most recent quarters combined. That screen is why the index leans toward established businesses rather than speculative names.
How the Index Is Weighted
The S&P 500 is float-adjusted market-cap weighted. In plain terms, bigger companies count for more. A company's weight is based on the value of shares actually available to trade, so closely held shares owned by founders or governments are stripped out.
This has a practical consequence every beginner should understand: the index is heavily concentrated at the top. The ten largest companies now make up roughly 35% to 40% of the entire index, the highest concentration in decades, and the Magnificent Seven technology names alone drive much of the daily movement.
That concentration cuts both ways. When mega-cap tech rallies, the index climbs fast; when those names stumble, it feels the drop more than the average company would suggest. Owning the index is broad, but not perfectly even.
Trade US stocks from $1 with Gotrade so you can build an S&P 500 position gradually instead of saving up for a full ETF share first.
Ways to Invest in the S&P 500
You cannot buy the index directly, but you can buy a fund that mirrors it. The most popular route is an exchange-traded fund, or ETF, that holds all 500 stocks in the correct weights. Three ETFs dominate.
The three big S&P 500 ETFs
The Vanguard S&P 500 ETF and the iShares Core S&P 500 ETF both carry rock-bottom expense ratios, while the SPDR S&P 500 ETF is the oldest and most heavily traded. All three track the same index, so returns are nearly identical year to year.
How they differ
The main differences are cost and structure. As The Motley Fool notes, VOO and IVV charge a far lower fee than SPY, which matters when you hold for decades. SPY trades with the deepest liquidity that traders value, while long-term beginners usually favor the cheaper funds.
For a deeper side-by-side, our comparison of VOO, VTI, and SPY as S&P 500 ETFs walks through the tradeoffs for buy-and-hold investors.
Historical Returns and What to Expect
Over the long run, the S&P 500 has delivered an average annual return of roughly 10% before inflation, with dividends reinvested. Adjusted for inflation, the realistic figure is closer to 6% to 7%.
That 10% is an average, not a promise. In any single year the index can swing far above or below it, and stretches of down years do happen. It sits near record highs in 2026, but past performance never guarantees the next year, which is why a long time horizon matters.
The takeaway for beginners is to think in decades, not days. The S&P 500 has rewarded patient investors who kept buying through calm and turbulent markets alike.
Conclusion
The S&P 500 is the benchmark index for US stocks, a float-adjusted collection of 500 leading companies that captures most of the market's value. It is broad but concentrated at the top, and it has historically compounded at about 10% a year over the long run.
For a beginner, the simplest path is a low-cost S&P 500 ETF held patiently over many years. You do not need to pick individual stocks to share in America's growth story.
Trade US stocks from $1 with Gotrade and start your S&P 500 position with fractional shares, so you can begin on any budget instead of waiting for a full share.
FAQ
Is the S&P 500 the same as the 500 biggest US companies?
Not exactly, because a committee applies size, liquidity, and profitability criteria rather than a strict size ranking.
What is the difference between VOO, IVV, and SPY?
All three track the same index, but VOO and IVV charge lower fees while SPY offers the deepest trading liquidity.
What return can I expect from the S&P 500?
Historically it has averaged about 10% per year before inflation, though any single year can be much higher or lower.
Can I invest in the S&P 500 with a small amount of money?
Yes, fractional shares let you buy into an S&P 500 ETF from as little as $1 on Gotrade.
