Market capitalisation is the total value the market places on a company's equity: shares outstanding multiplied by share price. It is what all the stock is worth, not what the whole company is worth, because it ignores debt and cash entirely.
The mistake nearly everyone makes
Market cap is routinely described as what a company is worth. It is not. Buying every share does not buy the business free and clear, because the debt comes with it and the cash comes with it. What a buyer would actually pay is enterprise value: market cap plus debt, minus cash.
Worked example
Two companies both have 100 million shares at $20, so both have a $2,000M market cap. Company A holds $500M of cash and no debt. Company B holds $100M of cash and $800M of debt.
A: $2,000M + $0 − $500M = $1,500M enterprise value
B: $2,000M + $800M − $100M = $2,700M enterprise value
Identical market caps, and B costs 80% more to own outright. Any multiple built on market cap treats these as the same company.
Why share price on its own means nothing
A $500 share is not expensive and a $3 share is not cheap. Price is one of two inputs, and the other is share count, which management sets. A stock split can halve the price without changing anything about the company.
This is the single most common beginner error and it has an easy cure: never quote a share price without the market cap beside it.
The size categories
- Mega cap, above $200B. Dominant, widely covered, and unlikely to multiply from here.
- Large cap, $10B to $200B. Established, liquid, thoroughly analysed.
- Mid cap, $2B to $10B. Often the sweet spot: proven business, room to grow, thinner analyst coverage.
- Small cap, $300M to $2B. Less efficient pricing, higher volatility, more work.
- Micro cap, below $300M. Thin liquidity and much weaker disclosure.
The boundaries are conventions rather than rules, and they matter mainly because coverage thins as size falls. Less coverage means more mispricing, which is opportunity and risk in the same fact.
Diluted, not basic
Use diluted shares outstanding, which includes stock options and convertible securities that will become shares. For companies paying heavily in equity, the gap between basic and diluted is real money, and it is the diluted figure that reflects what you will actually own.
Check the trend too. A share count rising steadily means your slice is shrinking even when the market cap holds, which is exactly the situation step five of reading an income statement is designed to catch.
Size tells you less than phase does
A $5B company can be in hyper growth or in decline, and the market cap will not tell you which. Phase Check reads the financials for any US-listed company and places it on the lifecycle in seconds.
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Frequently asked questions
Related
- Stock splits, why share price alone tells you nothing
- P/E ratio, a multiple built on the equity value
- How to read a balance sheet, where the debt and cash come from
- Investing glossary, every term used above, defined in plain English