What is the S&P 500?
The S&P 500 (US 500) is a stock market index that tracks 500 leading US companies. It covers approximately 80% of available US market capitalisation and is commonly used as a benchmark for the performance of large-cap US equities.
S&P Dow Jones Indices (S&P DJI) maintains the The S&P 500 index, and companies need to meet a range of eligibility requirements before they can be considered for inclusion.
CFDs are complex instruments and come with a high risk of losing money rapidly due to leverage. 79.75% of retail investor accounts lose money when trading CFDs with this provider.
Key takeaways
- The S&P 500 tracks 500 leading US companies and covers approximately 80% of available US market capitalisation.
- It’s float-adjusted market-capitalisation weighted, which means larger companies generally have more influence on the index than smaller ones.
- Companies need to meet criteria covering factors such as size, liquidity, public float and financial viability, and S&P DJI’s Index Committee makes the final selection.
- The modern 500-stock S&P 500 launched in March 1957, although its history can be traced to an earlier US stock index created in 1923.
- As of 31 July 2026, Nvidia, Apple, Microsoft, Amazon and Alphabet Class A were the five largest constituent securities by index weight. The 10 largest constituents together accounted for 37.6% of the index.
Where have you heard about the S&P 500?
The S&P 500 is frequently cited in financial news when discussing US share prices, company earnings, interest rates, inflation, and broader market movements.
You may hear about the index when US equities reach new highs or move sharply following economic or company news. Because it covers a large share of the US equity market, it’s often used as a reference point for the performance of major US-listed companies.
However, the S&P 500 isn’t the same thing as the US economy. It focuses on large listed companies, so its movements don’t necessarily reflect conditions for smaller companies, private businesses, households or the wider economy.
What you need to know about the S&P 500
The S&P 500 is designed to measure the large-cap segment of the US equity market.
‘Large-cap’ refers to companies with relatively high market capitalisation – broadly, the total market value of their shares.
Although the index comprises 500 companies, it can include slightly more than 500 individual securities. Some companies have more than one eligible publicly traded share class, so each class can appear separately. S&P DJI reported 503 constituent securities as of 31 July 2026.
A related index, the ‘S&P 500 Top 50’, focuses on 50 of the largest S&P 500 companies by float-adjusted market capitalisation.
Which are the largest companies in the S&P 500?
The largest S&P 500 constituents change as share prices, market capitalisations and index membership change.
As of 17 August 2026, the ten largest constituent securities by index weight were:
- Nvidia (NVDA)
- Apple (AAPL)
- Microsoft (MSFT)
- Amazon (AMZN)
- Alphabet Class A (GOOGL)
- Broadcom (AVGO)
- Alphabet Class C (GOOG)
- Meta Platforms (META)
- JP Morgan (JPM)
- Berkshire Hathaway (BRK.B)
The top 10 constituents accounted for 37.6% of the index. The largest constituent represented 7.6% (S&P Global, accessed 17 August 2026):.
How is the S&P 500 weighted?
The S&P 500 uses float-adjusted market-capitalisation weighting, meaning each constituent's index weight is proportional to its float-adjusted market value (S&P Global, accessed 17 August 2026).
Market capitalisation is broadly calculated by multiplying a company’s share price by the number of shares it has issued. The float adjustment then considers shares available for public trading, rather than including certain restricted or closely held shares (Cirrus, accessed 17 August 2026).
In simple terms, the greater a company’s float-adjusted market capitalisation, the greater its index weight.
For example, if a very large constituent and a much smaller constituent both move by 5%, the larger company will generally have a greater effect on the S&P 500’s overall movement.
This weighting helps explain why developments affecting a relatively small number of large companies can sometimes have a noticeable effect on the wider index (S&P Global, accessed 17 August 2026).
Which sectors lead the S&P 500?
S&P 500 companies are classified under the Global Industry Classification Standard (GICS), which divides the market into 11 sectors.
As of 30 June 2026, the sector breakdown was:
| Sector | Index weight |
|---|---|
| Information technology | 38% |
| Financials | 11.8% |
| Communication services | 9.7% |
| Consumer discretionary | 9.3% |
| Industrials | 8.9% |
| Health care | 8.9% |
| Consumer staples | 4.6% |
| Energy | 3% |
| Utilities | 2.2% |
| Materials | 1.8% |
| Real estate | 1.8% |
Figures are rounded and sector weights change as share prices and index composition change. Sector weights vary considerably. Information technology represented more than a third of the index at this date, while several sectors each represented less than 5% (Charles Schwab, 17 August 2026).
How does a company join the S&P 500?
Being one of the largest US-listed companies doesn’t automatically qualify a company for the S&P 500. S&P DJI applies several eligibility requirements, while its Index Committee selects constituents from eligible companies. It also considers sector balance when making selections (S&P Global, accessed 17 August 2026).
Some of the main criteria include:
- Size – S&P DJI’s July 2026 methodology sets the minimum company-level market capitalisation for an S&P 500 candidate at $22.7bn. It reviews this threshold each quarter and updates it when needed.
- Public float – eligible S&P Composite 1500 companies generally need an investable weight factor of at least 0.1, meaning a sufficient proportion of their shares must be available to public investors.
- Liquidity – a candidate should generally have traded at least 250,000 shares in each of the previous six months and meet a float-adjusted liquidity ratio of at least 0.75 when added.
- Financial viability – GAAP net income from continuing operations generally needs to be positive for both the latest quarter and the latest four consecutive quarters combined. Equity REITs have specific provisions covering net income and/or funds from operations.
- Listing and domicile – candidates must meet US domicile and eligible US exchange-listing requirements, alongside rules covering company and security type. IPOs generally need at least 12 months of trading on an eligible exchange before they can be considered, although specified exceptions apply.
These are eligibility requirements rather than an automatic formula for inclusion. S&P DJI’s Index Committee retains discretion over constituent selection. Criteria can change, S&P DJI’s current methodology provides the most up-to-date requirements.
Sources: S&P Global, Investing.com. Accessed 17 August 2026.
How often do companies in the S&P 500 change?
There’s no scheduled reconstitution of the S&P 500. S&P DJI can change its composition when required by corporate actions or other market developments S&P Global (accessed 17 August 2026).
Falling below a current eligibility threshold doesn’t automatically remove an existing constituent. S&P DJI states that its eligibility rules are principally ‘addition criteria’, and it aims to avoid unnecessary turnover in index membership (S&P Global, accessed 17 August 2026).
What can affect the S&P 500?
The index can respond to many of the same factors that affect the share prices of its constituent companies, including:
- Company earnings and forecasts
- Interest-rate decisions and expectations
- Inflation and employment data
- Changes in economic growth
- Political and geopolitical developments
- Movements in currencies and commodity prices
- Developments affecting major industries or individual companies
The effect of each factor can vary. Because the index is weighted by float-adjusted market capitalisation, developments affecting larger companies or sectors may have a greater effect than those affecting smaller constituents (S&P Global, accessed 17 August 2026).
How has the S&P 500 performed historically?
Long-term S&P 500 performance figures vary depending on the period measured and whether dividends are included.
According to S&P global data, the index closed at 2,182.22 on 17 August 2016 and generally trended higher over the following years, despite several periods of sharp volatility. It reached 3,386.15 on 19 February 2020 before falling to 2,237.40 on 23 March as the Covid-19 pandemic disrupted global markets.
The S&P 500 later recovered, reaching 4,793.06 on 29 December 2021. In 2022, higher inflation and aggressive US Federal Reserve rate rises coincided with renewed pressure, with the S&P 500 falling to 3,577.03 on 12 October.
Further gains followed in 2023 and 2024, with technology shares, artificial-intelligence-related demand and Federal Reserve rate cuts among the factors supporting US equities. The index then fell to 4,982.77 on 8 April 2025 amid uncertainty over US tariffs, before recovering later in the year.
The S&P 500 closed at 7,785.76 on 14 August 2026, the latest figure in the supplied data – around 256.8% above its 17 August 2016 close.
Returns can vary substantially over shorter periods, including periods of loss. Past performance is not a reliable indicator of future results.
A brief history of the S&P 500
The S&P 500 developed from earlier US stock indices before taking its modern form in 1957.
- 1923: Standard Statistics Company developed a weekly stock index covering 233 US stocks.
- 1926: the index was reformulated as a daily Composite Stock Index containing 90 stocks.
- 1957: the modern 500-stock S&P 500 debuted on 4 March 1957.
- 1982: CME launched futures on the S&P 500.
- 1983: Cboe introduced options based on the S&P 500 Index.
- 1993: SPY launched as the first US-listed ETF, designed to track the S&P 500.
These developments broadened the ways market participants could follow or gain exposure to the index, while its constituent mix continued to evolve.
Sources: Reuters, 2013; S&P Global, accessed 17 August 2026.
How can you get exposure to the S&P 500?
You can’t buy the S&P 500 index itself. It’s a calculated benchmark rather than an asset.
Different financial products can provide exposure to the index or its price movements, including:
- Index funds and exchange-traded funds (ETFs) designed to track the S&P 500
- Futures contracts based on the index.
- Options linked to the S&P 500 or related products.
- Contracts for difference (CFDs) that allow traders to take a position on the index’s price movements without owning its constituent shares.
Learn more about how ETFs work in our ETFs guide.
S&P 500 CFDs on Capital.com
On Capital.com, the S&P 500 CFD market is available as the US 500 (US500). A CFD lets you take a position on changes in the market’s price without owning the companies in the underlying index.
Index comparison: S&P 500 vs Dow Jones vs Nasdaq-100
The S&P 500 (US 500), Dow Jones Industrial Average (US Wall Street 30), and Nasdaq-100 (US Tech 100) are commonly followed US stock-market indices, but they cover different groups of companies and use different weighting methods.
| Context | S&P 500 | Dow Jones Industrial Average | Nasdaq-100 |
|---|---|---|---|
| Main coverage | 500 leading large-cap US companies | 30 major US companies selected by committee discretion, excluding transportation and utility firms | 100 of the largest Nasdaq-listed non-financial companies |
| Weighting | Float-adjusted market capitalisation | Share price, summed and divided by the Dow Divisor | Modified market capitalisation, with a company's weight based on the lesser of its full listed market cap or three times its free-floating shares |
| Sector coverage | All 11 major GICS sectors | Broad coverage across 30 selected companies | Non-financial Nasdaq-listed companies |
| What has more influence? | Companies with larger float-adjusted market values | Companies with higher share prices, regardless of overall market value | Larger companies, subject to Nasdaq's modified weighting rules and capping mechanism |
Their different constituent groups and weighting methods mean they can respond differently to the same market conditions.
Sources: S&P Global, CME Group, Nasdaq. Accessed 17 August 2026.
CFDs are complex instruments and come with a high risk of losing money rapidly due to leverage. XX% of retail investor accounts lose money when trading CFDs with this provider. You should consider whether you understand how CFDs work and whether you can afford to take the high risk of losing your money.
FAQ
What is the ticker symbol for the S&P 500?
S&P DJI uses SPX as the ticker for the S&P 500 price-return index. Other financial data services may display different symbols, so the ticker you see can depend on the platform or data provider. On Capital.com, the related CFD market is called US 500 (US500), which tracks the live S&P 500 price.
Who maintains the S&P 500?
S&P Dow Jones Indices (S&P DJI) maintains the index. Its US Index Committee selects S&P 500 constituents from companies that meet the index’s eligibility requirements.
How often is the S&P 500 updated?
S&P DJI calculates the S&P 500 in real time while the relevant markets are open. The companies in the index don’t change continuously. S&P DJI updates membership when needed, including after corporate actions or other market developments.
Can you invest directly in the S&P 500?
No. The S&P 500 is an index rather than an asset you can own directly. Index funds, ETFs and derivatives can provide exposure to it. Capital.com also offers a CFD market based on the S&P 500 under the name US 500 (US500). Each type of product has different characteristics and risks, so the type of exposure matters when comparing them.
Why does the S&P 500 sometimes have more than 500 securities?
The index targets 500 constituent companies, but a company can have more than one eligible publicly listed share class. Each eligible share class can be represented separately. S&P DJI reported 503 constituent securities as of 31 July 2026.
How often do S&P 500 companies change?
There’s no scheduled reconstitution of the S&P 500. S&P DJI can add or remove companies when needed, including following corporate actions or other market developments. Falling below a current addition requirement doesn’t automatically mean an existing constituent will be removed.