What is market cap?
In one line: Market cap, short for market capitalization, is the total value of a company's shares: the share price multiplied by the number of shares.
A simple example
A company has 500 million shares. Each one trades at $40.
500,000,000 × $40 = $20 billion. That's its market cap.
If the price rises to $44, the market cap becomes $22 billion. Nothing about the business changed that day. Only the price people are willing to pay did.
Large, mid and small cap
These are rough labels. Different sources draw the lines a bit differently.
| Label | Market cap (rough) | Often feels like |
|---|---|---|
| Large cap | Over $10 billion | Steadier, heavily traded |
| Mid cap | $2 billion to $10 billion | In between |
| Small cap | $300 million to $2 billion | Bigger daily swings |
| Micro cap | Under $300 million | Thin trading, wide spreads |
Why it matters
Market cap tells you how big a company is. That shapes how it trades. Smaller companies often move more each day, which means more Volatility. Very small ones may have little Liquidity, so the Spread is wider and orders can fill worse.
It also decides how much a stock moves an Index. In the S&P 500, the biggest companies count the most. More in what moves stock prices.
A common mistake
Judging a company by its share price. A $500 stock isn't "bigger" or "more expensive" than a $20 stock. If the $20 company has 10 billion shares, it's worth $200 billion. The $500 company with 100 million shares is worth $50 billion.
Price per share alone says little. Market cap, and ratios like the P/E ratio, tell you more.
Questions
Is a higher market cap better?
Not better or worse, just different. Large caps tend to be steadier. Small caps can move faster in both directions.
How do you find a company's market cap?
Most stock pages and charting platforms list it next to the price. It updates as the share price moves.
What is float?
Float is the number of shares free to trade, leaving out shares held by insiders that are locked up. A small float can make a stock jumpier.
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