Market capitalization is equal to the share price multiplied by the number of shares outstanding.   Since outstanding stock is bought and sold in public markets, capitalization could be used as an indicator of public opinion of a company's net worth and is a determining factor in some forms of stock valuation.
Market cap only reflects the equity value of a company. A firm's choice of capital structure has a significant impact on how the total value of a company is allocated between equity and debt. A more comprehensive measure is enterprise value (EV), which gives effect to outstanding debt, preferred stock, and other factors. For insurance firms, a value called the embedded value (EV) has been used.
Market capitalization is sometimes used to rank the size of companies. It is also used in ranking the relative size of stock exchanges, being a measure of the sum of the market capitalizations of all companies listed on each stock exchange. The total capitalization of stock markets or economic regions may be compared with other economic indicators (e.g. the Buffett indicator). The total market capitalization of all publicly traded companies in 2020 was approximately US$93 trillion. 
Total market capitalization of all publicly traded companies in the world from 1975 to 2020. 
|Year||World market cap
(in mil. US$)
|World market cap
(% of GDP)
|Number of listed|
Market cap is given by the formula , where MC is the market capitalization, N is the number of shares outstanding, and P is the market price per share.
For example, if a company has 4 million shares outstanding and the closing price per share is $20, its market capitalization is then $80 million. If the closing price per share rises to $21, the market cap becomes $84 million. If it drops to $19 per share, the market cap falls to $76 million. This is in contrast to mercantile pricing where purchase price, average price and sale price may differ due to transaction costs.
Not all of the outstanding shares trade on the open market. The number of shares trading on the open market is called the float. It is equal to or less than N because N includes shares that are restricted from trading. The free-float market cap uses just the floating number of shares in the calculation, generally resulting in a smaller number.
Traditionally, companies were divided into large-cap, mid-cap, and small-cap.[ citation needed]  The terms mega-cap and micro-cap have also since come into common use,   and nano-cap is sometimes heard. Different numbers are used by different indexes;  there is no official definition of, or full consensus agreement about, the exact cutoff values. The cutoffs may be defined as percentiles rather than in nominal dollars. The definitions expressed in nominal dollars need to be adjusted over decades due to inflation, population change, and overall market valuation (for example, $1 billion was a large market cap in 1950, but it is not very large now), and market caps are likely to be different country to country.
The term market capitalization has also been applied to cryptocurrencies in recent years.   Unlike the money supply of a fiat currency, a cryptocurrency market cap is denominated in some other currency.
- List of public corporations by market capitalization
- List of countries by stock market capitalization
- Market price
- Shares authorized
- Treasury stock
- "Market highlights for first half-year 2010" (PDF). World Federation of Exchanges. Archived from the original (PDF) on July 22, 2013. Retrieved May 29, 2013.
- "Market Capitalization Definition". Retrieved April 2, 2013.
- "Financial Times Lexicon". Archived from the original on September 25, 2016. Retrieved February 19, 2013.
- "Market capitalization of listed domestic companies (current US$) | Data". data.worldbank.org. Retrieved September 20, 2021.
- "Mega Cap Definition". Retrieved April 2, 2013.
- "Micro Cap Definition". Retrieved April 2, 2013.
- "Definition of Market Capitalization". Archived from the original on October 1, 2020. Retrieved August 3, 2008.
- Popper, Nathaniel (September 12, 2018). "When Cryptocurrencies Fluctuate, He Uses These Tech Tools to Keep Track". The New York Times. Retrieved August 13, 2021.
- Vigna, Paul (January 23, 2018). "The Programmer at the Center of a $100 Billion Crypto Storm". wsj.com. Wall Street Journal. Retrieved August 13, 2021.
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