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What is Sensex: The Complete Guide

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What is SENSEX? 

‘What is Sensex’ is one of the many questions people have. Sensex meaning translates to Stock Exchange Sensitive Index. It’s a benchmark index of the Bombay Stock Exchange (BSE), India’s oldest and premier stock exchange. The actual name of the index is S&P BSE Sensex.

The Sensex comprises 30 stocks, representing the most traded stocks with the highest market cap. These companies represent diverse sectors like banking, automobiles, pharmaceuticals, energy, and technology, offering a snapshot of the country’s economic pulse.

Investors, analysts, and policymakers track the Sensex closely as it reflects the investor sentiment, overall stock market performance, and the economy’s general health.     

 How is the Sensex Calculated?

Calculating the Sensex involves the following steps:

  • The calculation of the Sensex begins with picking 30 of the most actively traded stocks that represent a broad market and its sectors.
  • The market cap of these 30 stocks is derived from the product of the current market price and the outstanding shares.   
  • Then, the free-float market cap is worked out. Free-float market capitalization is the value of a company derived from shares held publicly. This value does not include shares held by promoters, government entities, and other strategic investors.
  • The index is then computed by adding the free-float market cap of the 30 selected stocks and dividing this value by a predefined base value. The resulting value is the Sensex.
  • The Sensex is updated biannually to make it relevant to reflect the market dynamics.   

  The formula is Sensex = (Total free-float market capitalization / Base market capitalization) * Base index value.


  • Free-float market capitalization refers to the shares available for trading, excluding shares held by strategic investors.
  • The base market capitalization is the market cap of a company.
  • and  Base index value is the value for the calculation of the index. In this case, it is 100, with the base year as 1978-79.

As of 28 December 2023, the Sensex rate was 75,410 points. 

How to Invest in Sensex?

It is not possible to invest in the Sensex market directly. One can invest in it by opening a brokerage account and investing in the 30 stocks that comprise the index. This is equity investment. Alternatively, one can invest through mutual funds, index futures and options, and ETFs. 

To invest in the Sensex, one must first have a bank account that will eventually be linked to the trading account to enable seamless fund transfers and withdrawals. Also, the Securities and Exchange Board of India (SEBI) has mandated that all physical securities be transferred to demat form. Hence, even a Demat account is a must. 

Opening a Demat Account

Having a Demat account is one of the primary requirements of trading in the stock market. The Demat account stores the securities electronically; thus, an investor can access them anywhere.    

A Demat account is easy to open online after following these steps:

  • Select a reputed and registered Depository Participant.
  • Fill out the online application form by providing all the relevant personal and bank details.
  • Upload the relevant documents.
  • Do an in-person verification by recording a video of yourself reading your PAN number and address and submitting it.
  • Sign your application digitally. 
  • Submit the form.

Opening a Trading Account

A trading account is the link between your bank and your Demat account. A trading account allows investors to buy and sell shares and is particularly essential for Futures  & Options. Opening a trading account involves the following steps:

  • Choose a stockbroker after evaluating the brokerage rates and the services offered.
  • Fill out the account opening and KYC forms available online. Submit the KYC documents. If opting for Futures & Options, provide Income proof, too.
  • Do an in-person verification by recording a video of yourself reading your PAN card number. 
  • Sign the online application form using an Aadhaar-registered mobile number.
  • Submit the form.
  • Upon verification by the broker, you will get your login credentials. 
  •  Before you begin trading, add some money to your trading account.
  • Place buy/sell orders.

Having a Bank Account

The first step to commencing any transaction in the finance world is to open a bank account. Opening a bank account can be done offline and online, too.  

When opting for the offline mode:

  • Visit the nearest bank branch and fill out the Savings Account opening form.
  • Submit the form along with the required documents.
  • On verification from the bank, your account kit, including the account number will be dispatched via post.

When opting for the online mode:  

  • Visit your chosen bank’s website.
  • Click on the tab ‘Open a Savings Account.’
  • Fill in all the relevant details. 
  • Upload relevant documents. 
  • Click ‘Submit’.

Milestones of Sensex India

Ever since its inception, the Sensex has achieved significant milestones. They are as follows:

  • Early Years (1875-1985):
  • 1875: The Native Share & Stock Broker’s Association is formed, marking the official establishment of the BSE.
  • 1921: Clearing House operations begin.
  • 1957: BSE gets permanent recognition under the Securities Contracts (Regulation) Act.
  • 1986: The S&P BSE SENSEX, India’s first equity index, is launched.
  • 1987: Investor’s Protection Fund (IPF) is introduced.

Modernization and Growth (1986-1999):

  • 1989: BSE Training Institute (BTI) is inaugurated.
  • 1990: S&P BSE SENSEX crosses 1000 mark.
  • 1992: The Securities and Exchange Board of India (SEBI) is established.
  • 1995: BSE On-Line Trading (BOLT) system is introduced.
  • 1996: First major S&P BSE SENSEX revamp occurs.
  • 1997: The Trade Guarantee Fund (TGF) and Brokers Contingency Fund (BCF) are introduced.
  • 1999: Central Depository Services Ltd. (CDSL) is established.

Expansion and Diversification (2000-2015):

  • 2000: Equity derivatives are introduced.
  • 2001: Stock options, index options, and S&P BSE Dollex 30 launched.
  • 2002: The Negotiated Dealing System (NDS) is established.
  • 2003: T+2 settlement is introduced.
  • 2004: S&P BSE SENSEX crosses 6000 for the first time.
  • 2005: BSE becomes a corporate entity.
  • 2006: The Indian Corporate Debt Market (ICDM) is launched.
  • 2009: BSE STAR MF, FASTRADE™, and new transaction fee structure are introduced.
  • 2010: Currency derivatives are introduced, the S&P BSE Shariah Index commences, and mobile-based trading is launched.

Recent Advancements (2016-Present):

  • 2016: BSE becomes India’s first exchange to be recognized as a Designated Offshore Securities Market by the SEC.
  • 2017: BSE launches the “BSE Startups” platform and becomes India’s 1st universal exchange with the launch of the commodity derivatives segment.
  • 2018: BSE launches chatbot “Ask Motabhai” and receives SEBI “No Objection” to act as a “Facilitator” in non-competitive bidding.
  • 2019: BSE StAR Mutual Fund introduces e-mandate facility, and BSE launches India’s first exchange-traded interest rate options.
  • 2020: BSE’s RFQ platform for debt securities goes live, and BSE becomes India’s first exchange to introduce and adopt India Good Delivery Standards for GOLD and SILVER: BIS IS 17278: 2019.
  • 2021: The S&P BSE Sensex crossed 60,000 to close at 60,048 points 
  • 2022: BSE Technologies Private Limited announces the launch of KYC Registration Agency (KYC KRA) and BSE creates history by launching Electronic Gold Receipts (EGRs) on Diwali during muhurat trading.
  • 2023: It crossed the 70,000 mark and was trading at over 75k level towards December end. 

Major Plunges in Sensex Stocks

The Sensex journey hasn’t been smooth sailing. Some significant plunges include:

  • 1992 Harshad Mehta Scam: Investor fraud shook the market, and Sensex crashed by 62%.
  • 2008 Global Financial Crisis: The global meltdown led to a 52% drop in Sensex.
  • 2015 Chinese Yuan Devaluation: Concerns about slowing Chinese growth triggered a 22% fall.
  • 2016: Demonetisation in India & Brexit: The demonetization shock to businesses and cash flow, coupled with global uncertainty caused by news of Brexit, led to the Sensex crashing by 1,689 points and 605 points, respectively. 
  • 2020 COVID-19 Pandemic: The initial lockdown fears caused a 38% plunge in Sensex.


Understanding the Sensex is an essential aspect of investing in the Indian stock market. As the snapshot of Sensex India health, it is a ready reckoner for the performance of the top 30 stocks and broadly of the economy’s overall health. Thus, understanding and interpreting the Sensex helps make investment decisions.

Know more about: HAPPY FORGINGS IPO

  1. How many companies are there in the Sensex?

    There are 30 companies that make up the Sensex. These companies are picked from various sectors and reflect the market and its sectors.

  2.  How is the Sensex calculated?

    Since 2003, the Sensex is being calculated using the Free Float Capitalization method. The index calculation begins with stock selection, computation of free-float market cap, followed by final index calculation. 

  3. How to invest in the Sensex?

    One can either invest directly in the stocks of the Sensex by opening a brokerage account or by way of ETFs, mutual funds, index futures and options.

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I’m Archana R. Chettiar, an experienced content creator with
an affinity for writing on personal finance and other financial content. I
love to write on equity investing, retirement, managing money, and more.

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