The short version
- The Sensex tracks 30 large, actively traded companies listed on BSE, weighted by free-float market capitalisation.
- It was set to 100 for the 1978-79 base year and has been published since 1986; it trades in the 09:15 to 15:30 India time session.
- A move in points means little without the percentage: 800 points is 1% of 80,000 but 2% of 40,000.
Sensex today is one of the most checked numbers in Indian finance: a single figure summing up how India's largest listed companies are faring during the trading day. GlixoTrade does not show live prices; this guide explains what the index measures, how it is calculated and how to interpret the numbers you see elsewhere, so that a headline about the index rising or falling means something specific.
What the Sensex tracks
The Sensex, short for Sensitive Index, follows 30 large and actively traded companies listed on BSE, the Mumbai exchange formerly known as the Bombay Stock Exchange. It is often called the BSE index, although BSE publishes many other indices too. The Sensex has been published since 1 January 1986, with its starting value of 100 set for the 1978-79 base year. It is operated by BSE's index business.
The 30 constituents are drawn from across sectors, such as banking, information technology, energy and consumer goods, and are reviewed periodically. Companies are selected on criteria including size, trading activity and listing history, so the membership changes over time as firms grow, shrink or merge.
How the value is calculated
The Sensex is weighted by free-float market capitalisation. For each company, only the shares available for public trading count; holdings by promoters, governments and other locked-in owners are left out. The index then adds up these free-float values and compares the total with the base period.
Worked example (illustrative figures)
A company has a total market value of ₹10 lakh crore, but 55% of its shares are held by its promoters. Only the 45% free float counts, so its weight is based on ₹10 lakh crore × 45% = ₹4.5 lakh crore. A larger company by total value can therefore carry less weight than a smaller one with more shares in public hands.
Because of this weighting, the biggest free-float companies move the index most. A sharp move in one heavyweight bank or technology stock can shift the Sensex more than several smaller members combined.
Sensex today: when the market is live
The Sensex market moves with BSE's regular equity session, 09:15 to 15:30 India time, Monday to Friday, excluding exchange holidays. During the session the index is recalculated continuously, which is what a Sensex live feed or a Sensex today live ticker displays. Outside those hours the figure you see is the last closing value. BSE also runs a short pre-open session before 09:15 in which opening prices are discovered.
Labels such as "Sensex now", "current Sensex", "todays Sensex" and "today Sensex rate" on market apps and news tickers all refer to the same thing: the latest calculated index value, usually shown with the change from the previous close in points and as a percentage. Check the timestamp; free feeds are sometimes delayed.
Reading points, percentages and charts
Headlines often quote moves in points, but percentages are more meaningful. If the index stood at 80,000, an 800-point fall would be 800 ÷ 80,000 = 1%. The same 800 points at a level of 40,000 would be 2%. As the index has risen over the decades, point moves have become larger without necessarily being more dramatic.
A Sensex chart can show day to day Sensex movements or decades of history. For long periods, a logarithmic scale is more honest: it shows equal percentage moves as equal distances, so early crashes are not flattened into a line. Remember that the Sensex is a price index; dividends paid by its companies are not included in the headline value, so its long-run returns understate what investors received with dividends reinvested.
What tends to move the index
Day-to-day changes reflect news about the heaviest constituents, such as quarterly results from large banks, IT services firms and energy companies. Beyond individual companies, the index responds to interest-rate decisions by the Reserve Bank of India, inflation data, the government's budget, flows of money from foreign investors, the rupee exchange rate and global conditions, including overnight moves in US and Asian markets and the price of oil, which India imports in large quantities. None of these links is fixed; the same kind of news can move the index differently depending on what markets already expected.
Sensex and Nifty 50
India's other headline index, the Nifty 50, is run on the NSE and tracks 50 companies, also weighted by free-float market capitalisation. The two usually move closely together because they share many of the largest companies, but they will not match exactly, and a day's percentage change can differ. Neither is "the" Indian market; both are samples of its biggest firms.
What the Sensex can and cannot tell you
The index is a useful summary of how large Indian companies are valued at a moment. It does not describe smaller companies, it is influenced heavily by a handful of heavyweights, and for foreign investors returns also depend on the rupee exchange rate. You cannot buy the Sensex itself, although index funds and exchange-traded funds that aim to track it are available in India, and futures and options on it trade on BSE.
For how share markets work in general, read the stock market for beginners, and see financial markets explained for how India's market hours compare with others.
Reader questions
How many companies are in the Sensex?
Thirty. They are large, actively traded companies listed on BSE, chosen from across sectors and reviewed periodically.
What time does the Sensex open and close?
It moves with BSE's regular equity session, 09:15 to 15:30 India time on trading days, after a short pre-open session. Outside those hours the quoted value is the last close.
What is the difference between the Sensex and the Nifty?
The Sensex tracks 30 BSE-listed companies; the Nifty 50 tracks 50 NSE-listed companies. Both use free-float market capitalisation and usually move in the same direction, but not by exactly the same amount.
Sources
- BSE and Asia Index, Sensex index methodology
- National Stock Exchange of India, market timings