Last updated: October 17, 2026
- Market capitalization formula
- Example: calculating market cap
- Large-cap, mid-cap and small-cap
- Market cap vs enterprise value
- How investors use market cap
- FAQ
- Related terms
Market capitalization formula
Market cap = share price x shares outstanding. It tells you what the market is collectively paying for the company's equity at a given moment, and it changes every time the stock trades. The figure is widely used to size companies, weight an index and group stocks for comparison.
In accounting, capitalization can also mean a company's capital structure (its mix of debt and equity), or the practice of recording a cost as an asset on the balance sheet rather than expensing it immediately. On stock sites, it almost always refers to market cap.
Example: calculating market cap
Suppose Company A trades at $80 with 500 million shares outstanding. Its market cap is $40 billion. Company B trades at $400 with 20 million shares, a market cap of $8 billion. Even though B's share price is five times higher, A is the larger company by market value. Share price alone says nothing about size.
If Company A's stock falls 10% to $72, its market cap drops to $36 billion, even though nothing changed on its balance sheet.
Large-cap, mid-cap and small-cap
Investors sort stocks into tiers such as mega-cap, large-cap, mid-cap, small-cap and micro-cap. The dollar cutoffs vary by index provider and shift over time, so treat them as rough guides. Large companies such as blue-chip stocks tend to have deeper liquidity and lower volatility, while small-caps may offer more growth potential with greater risk. Examples of mega-caps include Apple (AAPL).
Market cap vs enterprise value
Market cap ignores debt and cash. Enterprise value adds total debt and subtracts cash to estimate the cost of acquiring the whole business. Two firms with equal market caps can have very different enterprise values if one carries heavy debt. For valuation work, combine market cap with metrics such as the P/E ratio and enterprise value multiples.
How investors use market cap
Market cap helps set expectations and build a balanced portfolio. Fund managers use it to define their investment universe, such as a small-cap growth fund. Many major indexes are capitalization-weighted, meaning the largest companies have the biggest influence on index returns, so a handful of mega-caps can move the whole benchmark. Traders also consider market cap when judging how easily a position can be entered or exited, since larger companies usually have narrower spreads and higher daily trading volume. Finally, comparing a company's market cap with its revenue, earnings or cash flow gives a quick sense of how richly the market is valuing it relative to peers in the same sector.
Frequently asked questions
Does a higher stock price mean a bigger company?
No. Size depends on market capitalization, which multiplies price by shares outstanding. A low-priced stock with many shares can be much larger than a high-priced one.
How often does market cap change?
Market cap changes continuously during trading as the share price moves. It also changes when the share count changes through issuance or buybacks.
Related terms
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For information only, not investment advice. See the disclaimer.