Key Takeaways
- The BSE Sensex is India's oldest and most watched stock market index, comprising 30 of the largest companies on the Bombay Stock Exchange. This guide explains how Sensex works, how it is calculated, Sensex vs Nifty comparison, and what moves the Sensex.
What is the Sensex?
The S&P BSE Sensex (Sensitive Index) is India's most iconic stock market index, maintained by the Bombay Stock Exchange (BSE). It tracks the performance of 30 financially sound and well-established companies listed on the BSE, representing various sectors of the Indian economy.
Sensex was launched on January 1, 1986 with a base value of 100. As of 2026, it trades above 80,000 — an 800x growth in 40 years, representing approximately 15%+ CAGR.
How is the Sensex Calculated?
Like the Nifty 50, the Sensex uses free-float market capitalisation weighting:
Sensex Value = (Sum of Free-Float Market Cap of 30 stocks / Base Market Cap) × Base Index Value (100)
Free-float means only shares available for public trading are counted — promoter holdings and government stakes are excluded.
Which Companies Are in Sensex 30?
The Sensex 30 includes India's blue-chip companies. Current constituents include (weights approximate):
- Reliance Industries (~12%)
- HDFC Bank (~10%)
- ICICI Bank (~8%)
- Infosys (~7%)
- TCS (~6%)
- Bharti Airtel (~4%)
- Kotak Mahindra Bank (~4%)
- L&T (~3.5%)
- ITC (~3%)
- Axis Bank (~3%)
The composition is reviewed every 6 months by the BSE Index Committee.
Sensex vs Nifty 50: Key Differences
| Feature | Sensex | Nifty 50 |
|---|---|---|
| Exchange | BSE (Bombay Stock Exchange) | NSE (National Stock Exchange) |
| No. of stocks | 30 | 50 |
| Base year | 1978–79 (value 100) | 1995 (value 1000) |
| Derivatives | Less liquid | Most liquid in India |
| Global recognition | High (older, internationally known) | Very high (preferred by FIIs) |
Historical Sensex Milestones
- 1979: Base value 100
- 1992: Harshad Mehta bubble — crossed 4,000
- 2007: Crossed 20,000 for first time
- 2020: Crashed to 25,000 (COVID) and recovered to 47,000 by year end
- 2023: Crossed 65,000
- 2024: Crossed 80,000
- CAGR since inception: ~15%/year
What Moves the Sensex?
- RBI monetary policy: Rate decisions → bank stocks → Sensex
- FII/DII flows: Net buying or selling by foreign and domestic institutional investors
- Global markets: Dow Jones, S&P 500, Shanghai Composite
- INR/USD rate: Rupee weakness = FII outflows = Sensex falls
- Crude oil prices: India's largest import; high crude = inflationary = bearish
- Quarterly earnings: Results of Reliance, HDFC Bank, TCS dominate Sensex direction
