World Indices: What are Stock Indices, and How are They Calculated?

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Being familiar with stock market indices and how they are calculated is an essential element of your trading or investing journey as a stock market participant. While emphasizing the importance of understanding how indices are calculated and how they can help you improve your trading skills, this article will walk you through the process step by step.

What are Stock Indices?

An index is a metric or indicator of something in its most basic form. In terms of the stock or financial markets, world indices are a statistical measure of movement in a specific securities market. Stock market indexes are made up of a fictitious portfolio of securities representing a specific market or sector.

These indexes serve as a barometer for determining the market’s overall conditions and instruments for assisting investors in determining the market’s general trend. Investors use these indices to determine which stock sets they want to invest in.

It is widely assumed that investing in an index fund is preferable to investing in single individual stocks since it keeps costs low and eliminates the need to constantly monitor earnings reports from firms because stock ownership equates to ownership of a portion of the company. However, as a result, if you invest in a single firm and it fails or decreases slowly, your shares may become worthless. Also, the company in which you invest can get wealthy; both of these outcomes depend on various conditions.

On the other hand, investing in an index will balance the gain and, more critically, the risks. People who invest in an index can feel easy knowing that their portfolio comprises particular companies about whom they conducted extensive research.

How are Stock Indices Calculated?

Each stock in an index is given a different weighting based on its kind. Because the price of each stock represented in a stock index impacts the index’s total value, there are different ways of calculating how much weight each stock should be given.

However, the methods for calculating stock indexes are as follows:

Price Weighting

A Price Weighted stock index is one in which the percentage of a stock that makes up the index is proportional to the stock’s price. As a result, a stock trading at $500 will account for ten times more of the entire index than a stock trading at $50.

Basically, the stock price is multiplied by the number of shares outstanding to establish its weight in a value or price-weighted index. For example, if Stock X has ten million shares outstanding and is trading at $20, its weight index is $200 million (10×20).

Market-share weighted indices

 An index whose prices are determined by reference to the prices of individual stocks, with each such price-weighted for the number of shares outstanding.

For example, if the price of an index component stock changes, the effect on the index as a whole is proportional to the number of shares outstanding. This means that if a component company has more outstanding shares, price changes will have a greater impact on the index.

Equal weighting

For every stock in an index, the same weight will be assigned to it by the Equal-weighted stock indices, so a change in the share price of any company it contains will have the same impact on the index, no matter its size or market share.

Fundamental weighting

This weighted index is calculated by determining the economic size of each company that makes up the index, with the use of factors like revenues, cash flow, book value, and dividends. The index is then weighted to represent each stock’s economic size in the whole collection.

Float-adjusted weighting

The float-adjusted stock index is employed to exclude shares that are closely held, government-owned, or company-owned, but it only counts shares that are available to investors.

So, in the free-adjusted method of weighting, market capitalization is calculated by multiplying the price per share of each freely traded share by the number of freely traded shares.

Market capitalization/value weighting

Investors frequently assess a firm based on its market capitalization, which is calculated by multiplying its stock price by the number of shares outstanding. Because larger companies are more valuable, their market capitalization is higher.

Hence, capitalization-weighted is calculated by first multiplying the market price of each component by the total number of outstanding shares to arrive at the total market value. Then, the weighting of the company in the index is determined by the proportion of the stock’s value to the total market value of the index components.

That being noted, it’s important to also discuss how some of the indices are calculated one after the other. For the purpose of this article, we will be focusing on the three most popular world indices.


The Dow Jones Industrial Average (DJIA), for instance, is calculated by adding the stock prices of the index’s constituent businesses and dividing them by the divisor. When stock splits or dividends are added or removed from the index, the divisor changes when a firm is added or removed.


The Nasdaq 100 index is calculated based on the market capitalization of its companies, with the QQQ being disproportionately weighted toward large-cap firms.

The aggregate value of the index share weights of each index security, multiplied by the security’s last sale price, and divided by an index divisor, determines the index’s value. On this, no corporation can have more than a 24 percent weighting.

 S&P 500

The S&P 100 is a float-weighted index, which means that the index’s market capitalizations are modified by the number of shares available for public trading.

As such, the calculation multiplies the number of outstanding shares of each firm by the current share price or market value.

Closing Thoughts

Investors follow different indices in each country throughout the world. For example, in the United States, the three most common stock indexes for observing the performance of the US market are those mentioned above. Certain indices are particularly appealing to Indians and Chinese investors too.

Nonetheless, it is critical to be well-versed in how they might be measured and evaluated.

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