What is Sensex?
The Sensex (Sensitive Index) is India's oldest and most widely followed stock market index. It tracks 30 large, financially sound, and actively traded companies listed on the Bombay Stock Exchange (BSE). The Sensex was launched on 1 January 1986 with a base value of 100 (base year 1978–79), making it one of the oldest indices in Asia.
When you hear news anchors say "the market rose 500 points today," they are almost always referring to the Sensex. It is the single most popular barometer of Indian stock market health.
How is Sensex Calculated?
The Sensex uses a free-float market capitalisation-weighted methodology:
- Only shares available for public trading (not held by promoters, government, or strategic holders) are counted in the free-float market cap
- Companies with larger free-float market caps have higher index weightage
- The index value = (Sum of free-float market caps of 30 companies) / Base market cap × 100
Reliance Industries, HDFC Bank, and Infosys typically have the highest weights (5–12% each) due to their large free-float market caps.
Which 30 Companies are in Sensex?
The BSE Index Committee selects Sensex constituents based on free-float market cap, trading frequency, and sector representation. As of 2026, Sensex includes companies like Reliance Industries, TCS, HDFC Bank, Infosys, ICICI Bank, HUL, Bharti Airtel, ITC, L&T, Kotak Mahindra Bank, Bajaj Finance, Sun Pharma, Maruti Suzuki, Titan, Wipro, and others across banking, IT, energy, FMCG, and auto sectors.
The list is reviewed semi-annually. Companies are replaced if they no longer meet criteria.
Sensex vs Nifty 50 — Key Differences
- Exchange: Sensex = BSE. Nifty 50 = NSE
- Number of stocks: Sensex = 30. Nifty 50 = 50
- Base year: Sensex = 1978–79. Nifty = 3 November 1995
- Methodology: Both use free-float market cap weighting
- Correlation: Very high (>0.99). They move almost identically on most trading days
- Derivatives: Sensex futures/options trade on BSE. Nifty futures/options trade on NSE (far more liquid)
What is a "Sensex Point"?
One Sensex point represents a change in the aggregate free-float market capitalisation of the 30 companies. At Sensex levels of 80,000–90,000, a 1% move equals approximately 800–900 points. In earlier years (Sensex at 5,000), a 1% move was only 50 points — so raw point movements are meaningless without context. Always use percentage change.
Sensex Milestones
- 1,000 — July 1990
- 10,000 — February 2006
- 30,000 — February 2015
- 50,000 — January 2021
- 80,000 — June 2024
The journey from 0 to 10,000 took 30 years. The journey from 50,000 to 80,000 took just 3.5 years — reflecting India's economic acceleration and increased retail participation post-COVID.