Market capitalization is the total market value of a company’s outstanding shares — simply the share price multiplied by the number of shares. It is the standard way to measure a company’s size and the first number most investors reach for when comparing one business to another.
Market cap also sorts the market into bands: large-cap, mid-cap and small-cap, each with its own typical risk and liquidity profile.
Market cap counts only equity. Enterprise value adds debt and subtracts cash to value the whole business.
Suppose a company’s shares trade at $150 and it has 2,000M shares outstanding:
At $300B, this is a large-cap company. Note that market cap ignores the company’s debt entirely — for a buyout-style comparison you would use enterprise value instead.
Use market cap to size positions, compare companies, and segment the market by cap band. It is also the basis for most index weightings, so a handful of the largest companies can dominate a market-cap-weighted index.
Market cap matters most for risk and liquidity profiling — smaller-cap stocks tend to be more volatile and thinly traded — and for asset allocation across size segments.
Market cap reflects only equity, not the whole enterprise, so it understates the cost of acquiring a debt-laden company — use enterprise value there. It also moves with sentiment rather than fundamentals, and the shares actually available to trade (the float) can differ from total shares outstanding.