What is Sensex? BSE Sensex Explained Simply

Sensex is one of the two most important stock market indices in India, along with Nifty 50. If Nifty 50 is the scorecard of NSE, then Sensex is the scorecard of BSE (Bombay Stock Exchange). Every business news channel, every financial newspaper, and every market app shows Sensex as one of the primary indicators of how the Indian market performed on any given day.

Sensex — Full Form and History

Sensex stands for Sensitive Index. It was created by stock market analyst Deepak Mohoni and was first compiled on January 1, 1986. The base year of Sensex is 1978-79, and the base value was set at 100 points. Today, Sensex trades around 75,000 points — a growth of 750 times from its base value, reflecting the incredible growth story of the Indian economy over nearly five decades.

BSE itself is Asia's oldest stock exchange, established in 1875. Sensex is its flagship index and has been the traditional barometer of Indian market sentiment for decades, even before NSE and Nifty came into existence.

Which 30 Companies Are in Sensex?

Sensex tracks 30 of the largest and most liquid companies listed on BSE. These include household names like Reliance Industries, TCS, HDFC Bank, Infosys, ICICI Bank, Hindustan Unilever, Bharti Airtel, State Bank of India, Larsen and Toubro, and Bajaj Finance. The 30 companies represent multiple sectors including IT, banking, energy, FMCG, automobile, pharma, and telecom.

Like Nifty 50, the composition of Sensex is reviewed periodically. The Index Committee of BSE can add or remove companies based on market capitalization, trading volume, and other criteria. Over the years, many companies have entered and exited Sensex — for example, traditional manufacturing companies have been replaced by IT and financial services companies as the economy evolved.

How is Sensex Calculated?

Sensex uses the free-float market capitalization weighted method, similar to Nifty 50. The free-float market cap of all 30 companies is added up and divided by a number called the Index Divisor, which is adjusted for corporate actions like stock splits and bonuses. In simple terms, bigger companies have a larger impact on the index movement.

For example, Reliance Industries has roughly a 12 percent weight in Sensex. This means if Reliance stock goes up 1 percent and everything else stays flat, Sensex would go up about 0.12 percent. Conversely, a small-weight company like Nestle moving 1 percent would barely move the index.

Sensex vs Nifty 50 — Key Differences

Sensex belongs to BSE and tracks 30 companies. Nifty 50 belongs to NSE and tracks 50 companies. Sensex was launched in 1986, while Nifty started in 1996. Since Nifty covers 50 companies versus 30, it represents a broader section of the market. However, both indices share most of their top companies and move in the same direction about 95 percent of the time. For practical purposes, tracking either one gives you a good sense of the overall market direction.

In terms of trading volume, NSE handles about 90 percent of Indian equity trading volume, which makes Nifty more relevant for active traders. However, Sensex remains the more recognized name globally and is frequently quoted in international financial media.

Sensex Historical Milestones

Sensex crossed 1,000 for the first time in 1990. It reached 10,000 in 2006, 20,000 in 2007, and 30,000 in 2017. The 40,000 mark was breached in 2019, and 60,000 in 2021 during the post-COVID rally. In 2024, Sensex touched 80,000 for the first time. Each milestone represents years of corporate growth, economic reforms, and increased investor participation.

Track Sensex Live

You can track Sensex along with other major indices on our Live Market page. We display Sensex, Nifty 50, Bank Nifty, and sectoral indices with real-time data.

Disclaimer: This article is for educational purposes only. It is not financial advice. Please consult a SEBI-registered advisor before making investment decisions.