An index is a statistical measure that tracks the performance of a group of assets, such as stocks, bonds, or commodities, that represent a particular market or sector. It enables investors to identify market trends and compare performance.
Table of Contents
What Is An Index?
For example, the Nifty 50 in India tracks the performance of the top 50 companies listed on the National Stock Exchange.

Understanding Index
In finance, indexes are commonly used to track a statistical measure of the change in various security prices. It is useful because it helps investors understand how a specific market or sector is performing overall, rather than looking at individual companies.
By tracking an index, investors can compare their portfolio’s performance, identify trends, and make informed investment decisions. It also serves as a benchmark for mutual funds and other financial products.
Each index related to the stock and bond markets has its own calculation methodology, here are the most few most common indexes and calculations.
S&P 500 (Standard & Poor’s 500) – USA
- Tracks: 500 large companies listed on U.S. stock exchanges.
- Calculation: Weighted by market capitalization.
Formula:

Dow Jones Industrial Average (DJIA) – USA
- Tracks: 30 large, publicly-owned companies in the U.S.
- Calculation: Price-weighted index.

Nifty 50 – India
- Tracks: 50 leading companies listed on the National Stock Exchange (NSE).
- Calculation: Weighted by free-float market capitalization.
Formula:

Key Concepts for Calculation
Market Capitalization: Share price × Number of outstanding shares.
Free-Float Market Capitalization: Only includes shares available for public trading, excluding those held by promoters or large institutions.
Divisor: A number adjusted periodically to account for corporate actions and keep the index value consistent.
What Is an Index Fund?
An index fund is a type of investment fund that tries to match the performance of a specific market index, like the Nifty 50 or S&P 500. Instead of picking individual stocks, it invests in all the stocks in the index in the same proportion.
This makes it simple, low-cost, and great for long-term investing, as it grows along with the market. Index invetsing is a passive investing stratergy.
Mutual funds and ETFs are also an type of index as they seek to replicate the performance of an index.
Index Investing
“Indexing” is a type of passive fund management. Instead of actively stock picking and market timing—that is, selecting securities to invest in and planning when to buy and sell them—a fund portfolio manager creates a portfolio whose holdings mirror those of a specific index.
The idea is that by replicating the index’s profile—the entire stock market or a wide range of it—the fund will match its performance.
A popular index fund is the Vanguard S&P 500 ETF (VOO), which is similar to the S&P 500 Index.
What Are Some Bond Indexes?
Key Takeaways
Indexes in financial markets are often used as benchmarks to evaluate an investment’s performance against.