What is Sensex: Explore Meaning and How it is calculated

A comprehensive explanation of Sensex, including its definition, calculation methodology and importance.
What is Sensex: Explore Meaning and How it is calculated
3 mins
16 August 2023

The Sensex stands as a fundamental metric, commanding attention from investors and analysts alike. Serving as a vital indicator of market performance, the Sensex, formally known as the S&P BSE Sensex, embodies a sophisticated mechanism for evaluating the vitality and direction of the Indian stock market.

What is Sensex?

Sensex, or the S&P BSE Sensex, is the benchmark stock market index of India. It shows how well the 30 biggest and most traded stocks on the Bombay Stock Exchange (BSE) are doing. People often use it as a way to measure how the Indian stock market is performing.

How does the Sensex work?

The Sensex plays a crucial role in reflecting the movements of the Indian stock market and serves as an indicator of the overall health of the economy. Let’s delve into the details:

1. Composition:

  • The Sensex comprises 30 of the largest and most actively traded stocks listed on the BSE.
  • These 30 stocks are carefully selected to represent various sectors of the Indian economy.

2. Calculation:

  • The Sensex is calculated using a method called free-float capitalisation.
  • In this method, companies are weighted based on their share of the total market capitalisation of the index.
  • Larger companies have a greater impact on the index due to their higher market capitalisation.
  • The calculation involves dividing the free-float market capitalisation of the 30 companies by a number called the index divisor.
  • The index divisor ensures that the Sensex remains comparable over time, even when there are changes in the constituent stocks due to corporate actions or replacements.

3. Significance:

  • The Sensex is considered a barometer of investor sentiment and economic trends.
  • When the Sensex rises, it indicates that the prices of the underlying 30 stocks have increased, reflecting optimism in the market.
  • Conversely, a decline in the Sensex suggests that the prices of these stocks have fallen, signalling caution or pessimism.

How is Sensex calculated?

The Sensex is calculated by taking the sum of the closing prices of the top 30 stocks in the index, multiplied by their respective weights. The weights are based on the free-float market capitalisation of each stock, dividing this value by the Base market capitalisation, multiplying it by the base value of the index

The formula for Sensex:

Sensex = Free float market capitalisation of 30 companies / Base market capitalisation * Base value of the index.

For Sensex calculation, the base year to calculate Sensex is 1978-79 and the base value is static, Rs. 2501.24 crore is to be used as the base market capitalisation and a value is 100 is taken as base value

So, the final formula for calculation Sensex is:

Sensex = Free float Market Capitalisation of 30 firms / 25041.24 crores * 100

Free-float market capitalisation is the total market capitalisation of a company's shares that are available to the public for trading.

Let’s try to understand with an example, let's say that the Sensex is made up of 3 stocks, with the following weights:

  • Stock A: 25%
  • Stock B: 25%
  • Stock C: 50%

If the closing prices of the stocks on the day of calculation are Rs. 100, Rs. 200, and Rs. 300, respectively, then the free float market capitalisation would be calculated as follows:

Free Float Market Capitalisation = (25 * 100) + (25 * 200) + (50 * 300)

= 2500 + 5000 + 15000

= 22500

In this particulate case

Sensex will be = Free float market capitalisation of these 3 companies / Base market capitalisation * Base values of the index.
Sensex = 22500 / 25041.24 crores * 100

The Sensex value is calculated at the end of each trading day. The index is also updated intraday, but the intraday changes are not considered for the calculation of the Sensex value at the end of the day.

In simple terms, the Sensex is a measure of the overall performance of the 30 largest and most liquid stocks on the Bombay Stock Exchange (BSE). The higher the Sensex value, the better the performance of the Indian stock market.

How to invest in Sensex?

Investing in the Sensex involves investing in the underlying stocks that constitute the index. This can be achieved through various means:

  • Direct Investment: Investors can buy shares of the individual companies listed in the Sensex through a trading account, using a trusted broker like Bajaj Financial Securities Limited (BFSL).
  • Exchange-Traded Funds (ETFs): ETFs that track the Sensex provide an indirect way to invest in the index. These funds aim to replicate the performance of the index and offer diversification across multiple stocks.
  • Index Funds: Similar to ETFs, index funds passively track the Sensex's performance by holding the same stocks in the same proportions as the index.

Milestones of Sensex

The Sensex has witnessed several significant milestones in its history, reflecting the evolution of India's economy and financial markets:

Milestone Date
Launch of Sensex with a base value of 100 January 2, 1986
Crossing the 5,000 mark 01/10/99
Crossing the 20,000 mark 2007
Crossing the 21,000 mark 2008
Notable crashes: 1992 Harshad Mehta scam, 2008 financial crisis, COVID-19 pandemic Various
Current all-time high Present


Major plunges in the Sensex stocks

Date Cause Impact Points Lost
January 21, 2008 Market reacts to global financial crisis, records highest single-day loss Loss of 1408 points, highest since inception 1408 points
January 22, 2008 Continued market uncertainty, trading suspended for an hour Trading halt to mitigate further losses -
01/10/08 Intensification of global financial crisis Sensex hits 10-year low, closing at 8509.56 points -
2009 Satyam fraud scandal shakes investor confidence Loss of nearly 750 points 750 points


Difference between Nifty and Sensex

Nifty and Sensex are two of the most well-known stock market indices in India, often used as barometers to gauge the overall performance of the Indian stock market. However, there are some key differences between the two:

  Sensex Nifty
Composition The Sensex is composed of 30 of the largest and most actively traded companies listed on the Bombay Stock Exchange (BSE). It represents a diverse range of sectors. The Nifty, officially known as the Nifty 50, comprises 50 of the largest and most liquid stocks listed on the National Stock Exchange (NSE). It also covers various sectors of the economy.
Stock Exchange It is associated with the Bombay Stock Exchange (BSE), which is one of the oldest stock exchanges in Asia. It is associated with the National Stock Exchange (NSE), a relatively newer exchange known for its electronic trading platform.
Number of Companies It consists of 30 companies, making it a narrower index in terms of the number of constituents. It includes 50 companies, which provides a broader representation of the market.
Sector Representation Due to its smaller number of constituents, the Sensex may not cover as wide a range of sectors as the Nifty. With more companies, the Nifty offers a broader sectoral representation, potentially capturing a more comprehensive view of the market.
Impact of Large Companies Since it has fewer companies, the performance of a few large companies can have a significant impact on the overall movement of the index. The larger number of constituents in the Nifty may distribute the influence of individual companies more evenly.


The Sensex is more than just a numerical representation of stock prices; it reflects India's economic landscape and investor sentiment. As an essential benchmark, it provides insights into the performance of India's top companies across various sectors. Investors use Sensex to gauge market trends, make informed investment decisions, and monitor economic health. The index's journey through various milestones underscores the dynamism of India's financial markets and the broader economy, making it a critical tool for investors seeking exposure to India's growth story.

Use the Bajaj Financial Securities Limited (BFSL) Platform to invest in your choice of securities now.


While care is taken to update the information, products, and services included in or available on our website and related platforms/ websites, there may be inadvertent inaccuracies or typographical errors or delays in updating the information. The material contained in this site, and on associated web pages, is for reference and general information purpose and the details mentioned in the respective product/ service document shall prevail in case of any inconsistency. Subscribers and users should seek professional advice before acting on the basis of the information contained herein. Please take an informed decision with respect to any product or service after going through the relevant product/ service document and applicable terms and conditions. In case any inconsistencies are observed, please click on reach us.

*Terms and conditions apply

Standard Disclaimer

Investments in the securities market are subject to market risk, read all related documents carefully before investing.

Research Disclaimer

Broking services offered by Bajaj Financial Securities Limited (Bajaj Broking) | REG OFFICE: Bajaj Auto Limited Complex, Mumbai –Pune Road Akurdi Pune 411035. Corp. Office: Bajaj Broking., 1st Floor, Mantri IT Park, Tower B, Unit No 9 &10, Viman Nagar, Pune, Maharashtra 411014. SEBI Registration No.: INZ000218931 | BSE Cash/F&O/CDS (Member ID:6706) | NSE Cash/F&O/CDS (Member ID: 90177) | DP registration No: IN-DP-418-2019 | CDSL DP No.: 12088600 | NSDL DP No. IN304300 | AMFI Registration No.: ARN –163403.

Website: https://www.bajajbroking.in/

Research Services are offered by Bajaj Financial Securities Limited as Research Analyst under SEBI Registration No.: INH000010043.

Details of Compliance Officer: Ms. Kanti Pal (For Broking/DP/Research) | Email: compliance_sec@bajajfinserv.in/ Compliance_dp@bajajfinserv.in | Contact No.: 020-4857 4486 |

This content is for educational purpose only.

Investment in the securities involves risks, investor should consult his own advisors/consultant to determine the merits and risks of investment.

Frequently asked questions

What is Sensex in simple words?

Sensex is one of the most widely used stock market indices in India, which measures the performance of 30 major Indian companies listed on the Bombay Stock Exchange (BSE). It is calculated using the free-float market capitalisation method and used as a benchmark to gauge the overall health of the Indian stock market.

Why is Sensex used?

Sensex presents a broader picture of the BSE-listed stocks’ performance and can be utilised to assess the potential impact.

Why does the Sensex fluctuate?

Several factors can lead to fluctuations in the stock prices, including economic indicators, corporate earnings, international factors, and investor sentiment. And since the stock prices of the companies listed play a crucial role in determining Sensex’s value, it eventually fluctuates too.

What is the full form of Sensex?

The full form of Sensex is Sensitive Index.

Which is better Sensex or Nifty?

There’s no straightforward answer. It depends on your investment goals and preferences:

  • Nifty is broader, including more companies, while Sensex focuses on a smaller set of well-established companies.
  • Nifty may provide better diversification due to its larger number of constituents.
  • Sensex is often considered a historical benchmark and has a longer track record.
  • Investors often use both indices to gauge the overall market sentiment and diversify their portfolios.

Show More Show Less