What is the S&P 500? Meaning, companies and how to trade it

The S&P 500 is a stock market index that measures the performance of 500 leading large-cap companies listed in the United States, weighted by each company's market value. It is widely used as a benchmark for the US stock market and as a barometer of global investor sentiment. 

Alongside the Dow Jones Industrial Average (DJIA) and the Nasdaq Composite, it is one of the most quoted indices in global finance and a common shorthand for the health of the US  stock market.  Its influence extends beyond the US, as many of the largest companies in the index generate a significant share of their revenues outside the United States. 

Key Takeaways: 

• The S&P 500 tracks around 500 of the largest US companies, weighted by market value, and is a leading benchmark for the US market. 

• It covers roughly 80% of total US stock market value, so it's treated as a proxy for the wider economy. 

• The index is highly concentrated. As of 2026 the top ten companies make up close to 40% of its value, led by Nvidia. 

• It differs from the Dow (30 price-weighted stocks) and the Nasdaq Composite (2,500-plus, tech-heavy). 

• You can't buy the index directly, but you can take a position through CFDs, ETFs, futures and options. 

What is the S&P 500?

The S&P 500 is a stock market index that tracks the performance of the 500 (or so) largest companies in the US. It is a capitalisation-weighted index, meaning companies are selected for inclusion based on their total market value and given a weighting relative to their size – a US$50 billion company will have double the weighting of a US$25 billion company.

It was founded by financial services business and ratings agency Standard & Poor’s in 1957 to replace an earlier 90-stock index. Today it is owned by S&P Dow Jones Indices, which publishes more than 130,000 indices across the world, including the Dow Jones Industrial Average, the S&P/ASX 200 in Australia and the S&P/TSX in Canada.

Why traders watch the S&P 500?

With a combined market cap of more than US$70 trillion as of mid-2026, the S&P 500 represents around 80% of the US stock market.  It provides a useful indication of the performance and sentiment of the large-cap share market. As with the DJIA, the conventional wisdom is that if the S&P 500 is performing well, then so is the US economy (and vice versa). For that reason, it is closely followed by traders and investors around the world.

Many traders follow the S&P 500 as it is often seen as a reflection of overall US market sentiment and can influence the direction of global equities. The index is commonly monitored around major economic data releases and central bank policy announcements, and its movements may be linked to other asset classes such as currencies, commodities and bonds. It also forms the basis for products like CFDs, futures and options, is associated with volatility measures such as the VIX, and can provide indications of sector performance and technical levels, making it a widely referenced index in trading.

What companies are in the S&P 500? 

The S&P 500 is rebalanced quarterly, with the overseeing committee adding or removing stocks in response to share price movements and other eligibility factors.  

As of August 2026, the top ten companies in the index accounted for about 39% of the total market cap.  

Top 10 companies in the S&P 500 by market cap 

 S&P 500 sectors and weightings 
The S&P 500 groups its companies into 11 sectors under the Global Industry Classification Standard (GICS), and each sector's weight reflects the combined market value of its companies rather than an equal split. That's why the list is so top-heavy: information technology alone accounts for more than a third of the index, and the three largest sectors together make up over half of it. For traders, this means a move in big tech can pull the whole index with it, even when other sectors are flat. The full breakdown is below:  

1. Information technology (~36%) 

2. Financials (~12.5%) 

3. Communication services (~10%) 

4. Consumer discretionary (~9.7%) 

5. Health care (~9%) 

6. Industrials (~8.4%) 

7. Consumer staples (~5.1%) 

8. Energy (~3.4%) 

9. Utilities (~2%) 

10. Materials (~1.7%) 

11. Real estate (~1.7%) 

S&P 500 vs the DJIA vs the Nasdaq Composite 

These three indices are quoted regularly in stock market news reports, both within the US and across the world. Here is how they differ at a glance. 

The DJIA 

The Dow Jones is one of the oldest stock market indices in the world and predates the S&P 500 by several decades. It currently consists of 30 large blue-chip stocks that are considered representative of their industries and unlike the S&P 500, its composition rarely changes. It remains the most widely quoted index in the world, though many market watchers consider the S&P 500 to be the better barometer of the health of the stock market and the economy because of its broader composition. 

The Nasdaq Composite 

The Nasdaq Composite includes all of the over 2,500 stocks listed on the Nasdaq. Its composition is heavily concentrated in the tech sector, which makes up around 60% (according to Nasdaq Composite report of June 2026) of the index’s value, a much larger share than many other sectors. 

How to trade the S&P 500 index  

The S&P 500 is a calculated index rather than an asset that can be owned directly. Traders may gain exposure through a range of different CFD products offered by CMC Markets 

Trade S&P 500 index CFDs 

You cannot trade the S&P 500 directly, because the index is just a number that measures how its 500 companies are performing as a group. CMC Markets offers CFD products linked to the index. The price of the product generally reflects movements in the index.  

A contract for difference (CFD) is one such product. It is an agreement to exchange the difference in the index's price between the point you open a trade and the point you close it. Because these products are usually traded on margin, both potential profits and potential losses are magnified, which makes them higher risk. 

One of our top traded index products is the US SPX 500 – Cash. Depending on your trading strategy, you can go long or short, react to market moves in real time, and benefit from tight spreads on one of the most followed benchmarks in the world. 

Trade shares CFDs in S&P 500 companies 

A share CFD works the same way as an index CFD, but it tracks the price of a single company rather than the whole index. Instead of buying the shares outright and owning part of the business, you take a position on whether that company's share price will rise or fall, and settle the difference when you close the trade. 

Because the S&P 500 is weighted by size, its biggest constituents drive much of its movement. Taking positions on heavyweight names such as Nvidia, Apple, Microsoft, Google or Amazon means trading the same companies that carry the most influence over the index. A position on one or more of these mega-caps is an indirect way of expressing a view on the S&P 500, with the flexibility to focus on single companies rather than the broad market. 

Trade S&P 500 ETF CFDs

An exchange-traded fund (ETF) is a basket of assets you can trade like a single share. S&P 500 ETFs hold the index's constituents in different ways, and you can take a position on them through ETF-based CFDs, depending on your strategy. The Invesco S&P 500 Equal Weight ETF gives every stock the same weighting, reducing the dominance of mega-cap names. The Invesco S&P 500 Top 50 ETF does the opposite, narrowing exposure to the market's largest players. The Invesco S&P 500 Equal Weight Technology ETF offers a more concentrated view of the tech sector, which can be more volatile than the broader index. These products suit tactical strategies such as hedging, sector rotation, or positioning for a shift in leadership between large caps and the rest of the market. 

Trade S&P 500 futures and options 

Futures and options are contracts based on the future price of the index. A futures contract commits you to a position at a set date, while an option gives you the right, but not the obligation, to take one. You can trade S&P 500 futures directly or through CFDs, speculating on where the index will sit at a future point without owning the underlying assets. These are usually traded on margin, with the trader putting up part of the capital and borrowing the rest from the broker, which magnifies both potential gains and potential losses. 

Trade the S&P 500 CFDs in Australia with CMC Markets 

You can gain exposure to the S&P 500 through all four of these methods and more with CMC Markets. Trade on over 80+ cash and forward global indices  . New to index CFD trading? Practise first with a free demo account loaded with $10,000 in virtual funds, and work through the guides and market insights in our CFD Knowledge Hub.  

Open an account or try the demo to start trading the S&P 500. 

Disclaimer: This article provides general information only. It has been prepared without taking account of your objectives, financial situation or needs. It is not to be construed as a solicitation or an offer to buy or sell any financial instruments, or as a recommendation and/or investment advice. It does not intend to support an investment decision and it should not be relied upon by you in evaluating the merits of investing in any financial instruments. You should consider your objectives, financial situation and needs before acting on the information in this article. CMC Markets believes that the information in this article is correct, and any opinions and conclusions are reasonably held or made on information available at the time of its compilation, but no representation or warranty is made as to the accuracy, reliability or completeness of any statements made in this article. CMC Markets is under no obligation to, and does not, update or keep current the information contained in this article. Neither CMC Markets nor any of its affiliates or subsidiaries accepts liability for loss or damage arising out of the use of all or any part of this article. Any opinions or conclusions set forth in this article are subject to change without notice and may differ or be contrary to the opinions or conclusions expressed by any other members of CMC Markets.