Stocks & Equities · definition
Market Capitalization
Market capitalization is the total market value of a company's outstanding shares: share price multiplied by the number of shares. It is the standard yardstick for company size.
Market capitalization, "market cap", is the total value the stock market assigns to a company. It is calculated by multiplying the current share price by the number of shares outstanding. A company with 500 million shares trading at $40 has a market cap of $20 billion.
Key takeaways
- Market cap = share price × shares outstanding.
- It measures the market value of a company's equity, not the whole business or its assets.
- Companies are commonly grouped as large-cap, mid-cap and small-cap.
- Many stock indexes weight their members by market cap.
Size categories
Boundaries differ by index provider and shift over time, but a common convention groups listed companies roughly as: large-cap (above ~$10 billion), mid-cap (~$2-10 billion) and small-cap (~$250 million-$2 billion), with mega-cap and micro-cap at the extremes. Size matters descriptively because larger companies tend to be older, more widely followed and more heavily traded, while smaller companies historically show larger price swings.
What market cap is not
Market cap values only the equity of a company. It ignores debt: a firm with a $20 billion market cap and $15 billion of debt commands more total capital than the cap suggests (analysts use enterprise value to capture that). Market cap also says nothing about profitability, it reflects what buyers of shares are currently paying, which is why it is often read together with measures like the price-to-earnings ratio.
Role in indexes
Most major stock indexes, including the S&P 500 and MSCI World, weight companies by market cap (usually adjusted for shares actually available to trade, the "free float"). As a result, the largest companies move these indexes the most, and funds tracking them, including many ETFs, automatically hold more of the biggest firms.
Frequently asked questions
Does a stock split change market capitalization?
No. A split increases the share count and reduces the price proportionally; the total value is unchanged.
Is a higher market cap better?
Market cap describes size, not quality. A large cap signals that the market collectively values the equity highly, which is different from a judgement about the company's prospects.
Sources
This entry is for education only. Investing Value describes how financial concepts work; it does not provide investment, tax or legal advice, and nothing here is a recommendation to buy or sell any asset.