Market capitalization, or market cap, is the stock market’s current value of a company’s outstanding shares. It is calculated as share price multiplied by total outstanding shares. The figure describes a company’s size at market prices; it does not tell you on its own whether the stock is a good investment or likely to outperform.
How do you calculate market capitalization?
Market cap = current share price × total outstanding shares. Investor.gov defines it as the value of a corporation determined by multiplying the current public market price of one share by the number of total outstanding shares. See Investor.gov’s market capitalization glossary entry.
A simple example
Suppose a hypothetical company has 10 million outstanding shares, and each share trades for $5. Its market cap is $50 million:
10,000,000 shares × $5 per share = $50,000,000
This is illustrative arithmetic, not a reported company statistic. The example also shows why a share’s price alone does not reveal a company’s size: the number of shares matters too. A company with a lower-priced share can have a higher market cap if it has many more shares outstanding.
Recommended Free Tools
#1 Best Overall
What to check when calculating a live figure
- Use the share price and share count from a consistent date, since market prices can change.
- Check which share-count figure is being used. The basic formula uses total outstanding shares; company data may report share counts on different bases.
- Treat the result as a point-in-time estimate, not a fixed measure of the company’s worth.
What do large-cap, mid-cap, and small-cap mean?
These labels describe a company’s relative size or market value. Investor.gov’s glossary defines the terms but does not set universal numeric cutoffs. A label can therefore depend on the convention used by an index provider, fund, or other source. When someone calls a stock “large-cap” or “small-cap,” check whose classification they mean rather than assuming the label has one official boundary. See Investor.gov’s glossary of large-, mid-, and small-cap stocks.
Microcap stocks
In a September 30, 2016 bulletin, the SEC’s Office of Investor Education and Advocacy said companies with market caps below $250 million or $300 million are often called microcap stocks, while noting that many are far smaller. Those figures describe usage in that dated bulletin, not a universal or current dividing line. The SEC also warns that microcap companies may have less publicly available information, low trading volume and liquidity, and greater susceptibility to fraud or manipulation. Read the SEC bulletin on microcap stock basics for its discussion of these risks.
Rank #2
- Ideal for Gifting
- Ideal for a bookworm
- Compact for travelling
How does market cap affect an index?
In a market-cap-weighted index, companies with higher market caps make up a larger share of the index’s overall value. The SEC’s Office of Investor Education and Advocacy explains that securities with higher market capitalization account for a greater share of a market-cap-weighted index. That means their price movements generally have more influence on the index than those of smaller constituents, all else being equal.
That differs from a price-weighted index, where a constituent’s per-share price determines its weight. The SEC describes these approaches in its Investor Bulletin: Index Funds, dated August 6, 2018. Index weighting describes how an index is constructed; it does not establish that a larger company is better or that its shares will perform better.
What market cap cannot tell you
Market cap reflects share prices and outstanding shares. By itself, it does not tell you whether a company is profitable, financially sound, fairly valued, or likely to deliver stronger returns. Nor does it show what you would earn by buying a share. Investor.gov notes that stock prices can rise or fall and that investors can lose money; its stocks FAQ provides general context on stock ownership and risk.
Use market cap as a size description, then investigate the questions that matter to your decision: the company’s business, financial condition, valuation, and risks. A large market cap is not a quality score, and a small one is not proof of poor prospects. The metric does not separate future winners from losers.
Quick Recap
Best Value
- It can be a gift option
- Comes with secure packaging
- Helpful in various ways
Rank #4
A practical way to use market cap
- Calculate consistently: multiply the share price by total outstanding shares, using figures from a stated date and a clear share-count basis.
- Identify the classification source: if a stock is called large-, mid-, small-, or microcap, check the provider or convention behind that label.
- Keep the metric in perspective: use market cap to compare company size or understand index weighting, not as a stand-alone buy or sell signal.
Product prices and availability are accurate as of the date/time indicated and are subject to change. Any price and availability information displayed on Amazon at the time of purchase will apply.
