How to trade the S&P 500 (US500): weighting, sectors, hours and risk

Trading US500 means trading a CFD on the S&P 500, an index of about 500 of the largest US companies weighted by their market value. It is the benchmark most professional investors use for US shares, so it reflects the overall direction of the US stock market more closely than the 30-stock Dow or the technology-heavy Nasdaq 100. To trade it sensibly you need to know how it is weighted, which sectors drive it, when it is liquid, and how your broker's contract converts index points into money.

This page is about the index itself. For the general position sizing method for all major index CFDs, read index CFD position sizing; below there is only a short example.

What the S&P 500 is

The S&P 500 was launched in its current 500-stock form in March 1957 and is maintained by S&P Dow Jones Indices. CFD providers list it as US500, SPX500, US SPX 500 or similar. It tracks large US companies listed on the main US exchanges, both NYSE and Nasdaq, across every part of the economy.

Despite the name, it has slightly more than 500 lines, because a few companies have two classes of share in the index. Together its members account for a large majority of the total value of US-listed shares, which is why a fund tracking the S&P 500 is often used as a proxy for "the US market".

Our guide to what a stock index is explains the general principles. Here we focus on what makes this one distinctive.

How members are chosen

Membership is decided by the S&P index committee, not purely by a formula. Companies have to meet published eligibility criteria, which include:

• US domicile and a listing on an eligible US exchange.
• Minimum size, a market capitalisation threshold that the committee updates over time.
• Liquidity and free float, meaning enough shares available to the public and enough trading volume.
• Positive earnings, measured as the sum of the most recent four quarters and the most recent quarter on its own, using standard US accounting rules.

Meeting the criteria does not mean automatic inclusion; the committee also considers sector balance. Changes are announced when they happen, often a few days before they take effect, and frequently because a member has been taken over or has shrunk. Shares joining the index usually see heavy buying from index funds around the effective date. Our guide to index rebalancing explains how those flows work.

Cap weighting and what it means for traders

The S&P 500 is weighted by free-float market capitalisation: share price multiplied by the number of shares available to the public. The bigger a company's float-adjusted value, the more it moves the index.

Worked example: contribution to the index

Illustrative weights only. Suppose the index's largest member has a weight of 7% and a mid-sized member has a weight of 0.1%.

• The largest member rises 3%: contribution = 7% × 3% = 0.21% of the index.
• The mid-sized member rises 3%: contribution = 0.1% × 3% = 0.003%.

The same 3% move has seventy times the effect. On an index level of 6,000, the first is about 12.6 points and the second about 0.18 points.

Weights are rebalanced quarterly, on the third Friday of March, June, September and December, to reflect changes in share counts and float. Between rebalances, weights drift naturally with share prices: a company whose shares double will roughly double its weight.

Concentration

Because of cap weighting, the largest companies, which in recent years have mostly been big technology and communication firms, carry a large combined share of the index. The S&P 500 is far more diversified than the Nasdaq 100, but its moves on a given day can still be dominated by a few names. When the largest companies move one way and the "average" stock moves the other, the index follows the giants. Some investors watch an equal-weight version of the S&P 500 to see what the typical member is doing.

The 11 sectors

S&P classifies every member into one of 11 sectors under the Global Industry Classification Standard (GICS):

• Information technology
• Health care
• Financials
• Consumer discretionary
• Communication services
• Industrials
• Consumer staples
• Energy
• Utilities
• Real estate
• Materials

Information technology has been the largest sector by weight in recent years. The mix matters because sectors react differently to the same news. Rising bond yields may weigh on technology and real estate but help some financials; higher oil prices may lift energy while hurting airlines in industrials. When investors move money between sectors, the overall index can stay flat while the parts move a lot, a process described in our guide to sector rotation.

What moves US500

• US economic data. Payrolls, CPI, retail sales, PMIs and GDP all change expectations for growth and interest rates. The reaction depends on the surprise relative to forecasts, as explained in how economic data moves markets.
• The Federal Reserve. FOMC decisions, the statement and the press conference, and speeches by Fed officials. Changes in expected rates affect company borrowing costs and the valuation of future earnings.
• Earnings season. Four times a year, most members report results over about six weeks. Aggregate earnings growth and companies' guidance for future quarters are watched closely. See earnings season explained.
• Bond yields. Higher yields offer investors an alternative to shares and raise the discount rate on future profits. The relationship between yields and shares changes over time, but it is one of the most watched links in markets.
• Global risk sentiment. Because the S&P 500 is the world's reference equity index, geopolitical shocks, banking stress and big moves in other markets usually show up in it. The VIX is calculated from S&P 500 options and is often called the market's "fear gauge".

None of this produces reliable signals. The same headline can move the index differently depending on positioning and expectations.

When US500 trades

The shares in the S&P 500 trade on US exchanges from 09:30 to 16:00 New York time on weekdays, excluding US market holidays. That is usually 14:30 to 21:00 UK time. S&P 500 futures, including the widely traded E-mini contract on CME, trade nearly 23 hours a day from Sunday evening to Friday afternoon New York time, with a short daily break, and most providers quote US500 from them outside the cash session.

• 08:30 New York. Main US data releases, an hour before the cash open.
• 09:30 to 10:30. The opening hour is usually the most active, as the overnight news is absorbed by the full market.
• Late morning to early afternoon. Often calmer.
• 14:00. FOMC decisions on meeting days, followed by the press conference.
• 15:00 to 16:00. Volume rises into the close, when many funds trade at the closing price.
• Quarterly expiry. On the third Friday of March, June, September and December, index futures and options expire and the quarterly rebalance takes effect, which can produce heavy volume at the close.

Use the market hours tool to see the US session in your time zone. Outside the cash session, spreads on US500 are usually wider.

How US500 CFDs work

• Points. US500 moves in index points, usually quoted to one or two decimals. It sits at a much lower number than the Dow or Nasdaq 100, so a 1% move is fewer points.
• Value per point per lot. Set by the broker. Conventions such as 1, 10 or 50 dollars per point per lot are all used. Because the index level is lower, some providers use a larger multiplier for US500 than for US30. Check the contract specification.
• Cash or futures-based. A cash contract tracks a price close to spot and carries nightly financing; a futures-based contract has an expiry date and builds financing into its price. The S&P 500 is a price index, so cash positions get dividend adjustments when members go ex-dividend, and with about 500 members there are adjustments on many days. See trading index CFDs and dividends and corporate actions.
• Leverage. The S&P 500 is on ESMA's list of major indices, so EU retail clients can be offered up to 20:1 (5% margin).

A short sizing example

Illustrative numbers only. Account 20,000 dollars, risk 0.5% per trade = 100 dollars. US500 is at 6,000 and you want a stop 30 points away. Your broker's contract is 10 dollars per point per lot, lot step 0.01.

• Lots = 100 ÷ (30 × 10) = 0.333, rounded down to 0.33 lots.
• Money at risk = 30 × 10 × 0.33 = 99 dollars.
• Notional value = 6,000 × 10 × 0.33 = 19,800 dollars.
• Margin at 5% = 990 dollars.

A 30-point stop is 0.5% of the index. That might sit outside the noise on a quiet day and inside it on a busy one, so check the recent ATR. Use the position size calculator with your own broker's value per point, and the profit and loss calculator to see what a given move is worth.

Costs

• Spread, usually tightest during the US cash session.
• Commission, on some account types.
• Overnight financing on cash contracts, charged or credited each night and tripled to cover the weekend on one day of the week at many providers. The swap calculator helps estimate it.
• Dividend adjustments on cash positions.
• Currency conversion if your account is not in US dollars.

Over a few hours, the spread is the main cost. Over weeks, financing can be larger. Our guide to how to compare trading costs shows how to add these up.

Gaps and fast markets

Because US500 is quoted almost continuously on weekdays, the cash open gap is often small on a CFD. Gaps still happen at the weekend reopening, after the daily break, and when major news hits. US exchanges also have market-wide circuit breakers that halt trading after very large falls in the S&P 500, which our guide to trading halts and circuit breakers explains. A stop-loss order does not fix your exit price when the market jumps; read gap risk and weekend risk.

Reading the S&P 500 alongside other indices

Because the S&P 500 is the broadest of the big US indices, many traders use it as the reference point and compare the others with it.

• Against the Nasdaq 100. When the Nasdaq 100 is rising faster than the S&P 500, large technology and growth companies are leading. When the S&P 500 holds up better, money is often moving towards other sectors, such as financials, energy or defensive shares.
• Against the Dow. The Dow is price-weighted and much narrower, so differences between the two often come down to a few high-priced Dow members. A large gap between them on a single day is usually company news rather than a change in the broad market.
• Against an equal-weight version. If the cap-weighted index rises while the equal-weight version falls, gains are concentrated in the largest companies. Analysts call this narrow breadth. It is a description of what happened, not a prediction of what comes next.
• Against the VIX. A rising S&P 500 with a rising VIX is less common than the usual opposite relationship and can indicate demand for protection even as prices climb.
• Against bond yields and the dollar. Moves in Treasury yields and the dollar often explain why the index reacted to a data release the way it did.

A pre-trade checklist for US500

1. Know the scheduled events. Check the economic calendar for US data, FOMC meetings and the earnings dates of the largest members.
2. Measure the recent range. Use the daily ATR to judge whether your stop sits outside normal movement.
3. Confirm the contract. Value per point per lot, minimum size, lot step, cash or futures-based, and trading hours.
4. Check your other positions. Long US500 alongside long US30 and NAS100 is largely one bet placed three times; see correlation.
5. Plan for a gap. Decide whether you would be comfortable if the price opened well beyond your stop on Monday or after a major release.

Common mistakes with US500

• Assuming US500 is low-risk because it is diversified. The index is diversified; a leveraged CFD on it is not low-risk. A 5% fall against a position margined at 5% wipes out that margin.
• Using Dow-sized point stops. 100 points on the S&P 500 is a much larger percentage move than 100 points on the Dow.
• Ignoring the contract multiplier. A lot can be worth 1 dollar or 50 dollars a point. Check before trading.
• Forgetting dividend adjustments on short positions. A short cash US500 position is debited when members go ex-dividend.
• Trading the 08:30 or 14:00 releases with tight stops. Spreads widen and price can move through several levels at once.
• Mistaking the CFD for an index fund. A CFD costs financing every night and is designed for short-term trading; a long-term investor in the index would usually look at a fund. Our guide to ETFs explains the difference. Most retail CFD accounts lose money; see why most retail CFD traders lose.

Frequently asked questions

What is the difference between US500 and SPX500?

Usually nothing beyond the name. Both are broker labels for a CFD on the S&P 500. What does differ between providers is whether the contract is cash or futures-based, what a point is worth per lot, and the trading hours. Check the contract specification.

Is the S&P 500 really 500 companies?

It aims to hold 500 companies, but it has slightly more than 500 lines because a few companies have more than one class of share included. The number of companies can also be briefly different during membership changes.

Why does the S&P 500 move less in points than the Dow?

Because its level is much lower. A 1% move at around 6,000 is about 60 points, while 1% on the Dow at over 40,000 is more than 400 points. Compare percentages, not points.

When is the S&P 500 most volatile?

Typically around the 09:30 New York open, around major US data at 08:30, around FOMC decisions at 14:00 on meeting days, and in the final hour of trading. Earnings season and periods of market stress also bring larger ranges. Quiet periods often occur during the middle of the US day and during holiday weeks.

What leverage is allowed on US500?

EU retail clients can be offered up to 20:1 on the S&P 500 under ESMA rules, meaning a 5% margin requirement. Other regulators may differ, and professional clients may be offered more. See ESMA leverage limits.

Why is the VIX linked to the S&P 500?

The VIX is calculated from the prices of S&P 500 options and represents the market's expected volatility for the index over the next 30 days. It usually rises when the S&P 500 falls sharply, because demand for protective options increases. Our VIX guide covers it in detail.