The Sensex, or the Sensitive Index, isn’t just a number; it’s the oldest and most widely tracked stock market index in India, reflecting the market’s mood and movement daily. Managed by the Bombay Stock Exchange (BSE), it represents the performance of 30 of the largest and most actively traded stocks on the exchange.

These companies span key sectors of the Indian economy, offering a clear snapshot of overall market sentiment. But what makes a company eligible for the Sensex, and how is this important index calculated?
Understanding the Sensex Methodology
The Sensex is calculated using the free-float market capitalization method, which means it reflects the real market value by focusing only on shares available for public trading. This method considers only the shares readily available for trading in the open market, excluding promoter holdings, government stakes, and other locked-in shares. By focusing on the actively traded shares, this method ensures the index reflects real market conditions.
Sensex = (Free-float Market Cap of 30 Companies / Base Market Cap) × Base Index Value
The base year for the index is 1978–79, and we set the base index value at 100. Today, the Sensex fluctuates in real-time during market hours, reflecting changes in the share prices of the 30 component companies.
Why Sensex Matters as a Stock Market Index in India
The Sensex is widely regarded as a dependable indicator of the Indian stock market’s overall performance. It is used by mutual fund managers, financial analysts, and individual investors to track the health of the market. As a key stock market index in India, the Sensex not only mirrors investor sentiment but also provides valuable insights into the economic and industrial performance of the country.
Sensex Stock Selection Criteria
Becoming a part of the Sensex is no easy feat. The stock selection process ensures that only credible and significant companies are included in the index. To qualify, a company must have high market capitalisation based on the free-float method and exhibit strong liquidity with consistent trading volumes. It must represent a key sector of the economy and maintain a strong financial track record. Additionally, the company must comply with the regulations set by the Securities and Exchange Board of India (SEBI) and have a minimum listing history on the BSE.
Understanding the Sensex methodology and its stock selection criteria is crucial for anyone investing in or interested in the financial markets. As a vital stock market index in India, the Sensex continues to guide investment decisions and reflect the pulse of the economy.