What Is the CAC 40? How France's Benchmark Index Is Built
The Orque Markets team · 3 November 2026 · 5 min read · How we write
In short
- The CAC 40 is a free-float-weighted price index of 40 Paris-listed companies, capped at 15% per stock.
- A few heavyweights account for much of its moves.
- What one point is worth depends on your instrument, so read its specification first.
The CAC 40 is the number French news quotes every evening, yet most people who trade it could not name five of its members or say how it is calculated. Before you look at a single chart of it, it helps to know what the index actually is.
What the CAC 40 measures
The CAC 40 tracks 40 large companies listed on Euronext Paris. It was launched with a base value of 1,000 points at the end of 1987, and it is calculated and published by Euronext throughout the trading day.
Three facts shape how it behaves:
- Free-float weighting. Each company counts in proportion to its market capitalisation, using only the shares that actually trade (the free float), not the blocks held by founders or the state.
- A cap per stock. No single company may weigh more than 15% at a quarterly review, so one giant cannot become the whole index.
- A price index. The headline CAC 40 does not reinvest dividends. When a member pays one, the index loses that amount mechanically (see ex-dividend dates and index prices).
Who decides what is in it
An independent committee reviews the composition every quarter. Companies are ranked on free-float capitalisation and trading volume; a stock that falls far down the ranking can be replaced by a larger one. Changes are announced in advance on Euronext's website, which is the place to check the current list and weights.
Why a few names move the whole index
Because of the weighting, the top ten members usually account for well over half of the index. In recent years luxury, energy, aerospace and banking groups have dominated the top of the table. The practical consequence:
| What happens | Likely effect on the CAC 40 |
|---|---|
| One heavyweight luxury group falls sharply on results | The index can drop even if most members rise |
| Ten small members rise 2% each | Often a modest move in the index |
| Oil prices swing | Energy weights pass the move through |
The table describes tendencies, not rules: other members can offset any one stock on a given day.
When it trades
The cash market on Euronext Paris runs a continuous session from 09:00 to 17:30 Paris time, followed by a closing auction. Instruments that follow the index (futures, ETFs and other products) can have longer hours, and their price before 09:00 is an estimate of where the cash index will open. Our guide to European index hours in Paris time lays out the full day, and the market sessions tool shows it on a clock.
From index points to euros
The CAC 40 itself is just a number. What a one-point move is worth to you depends entirely on the instrument you use, so the first step is always to read its contract specification. Then position size follows from the stop, not from how confident you feel: sizing a position in index points walks through the formula, and the risk-reward calculator checks the trade before you take it.
How the CAC 40 differs from its neighbours
- DAX: 40 German companies, but a performance index that reinvests dividends (the DAX explained).
- Euro Stoxx 50: 50 leaders across the whole euro area, many of them French (Euro Stoxx 50 vs CAC 40).
The short version
The CAC 40 is a capped, free-float-weighted price index of 40 Paris-listed companies, reviewed every quarter, trading from 09:00 to 17:30. Know its heavyweights, its hours and its dividend season before you build any rule on it. Trading involves risk, and most retail traders lose money.
Questions people also ask
How many companies are in the CAC 40?
Forty companies listed on Euronext Paris, reviewed every quarter by an independent committee.
Does the CAC 40 include dividends?
No. The headline CAC 40 is a price index and drops when members go ex-dividend; separate total-return versions exist.
What are the CAC 40 trading hours?
Continuous trading on Euronext Paris runs from 09:00 to 17:30 Paris time, followed by a closing auction.
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