Size
Market Cap
Market capitalization is the market's price for the entire equity of the company.
Market cap is price times share count. It is the number people mean by 'how big is the stock.' It moves every second the price moves, and it moves when the company issues or repurchases shares. It is not cash in the company, and it is not the cost of buying the firm, because a buyer also deals with debt and cash. That fuller number is enterprise value.
Size changes what a stock can do in a portfolio. Mega caps anchor indexes. Small caps can grow faster and can also be harder to trade. Stocklytics lists market cap on every stock hero and lets screeners cut the market into large, mid, and small buckets so a strategy is not secretly a bet on one size.
Formula
Market cap = share price × shares outstanding
Live example
Apple Inc. (AAPL) last printed at $345.33 with a market cap of $5.04T. Market cap is the equity value you see above. Enterprise value would add net debt, which this quote row does not itemize.
Related
Enterprise Value · Shares Outstanding · Blue Chip
See it on a list: best stocks · screener
Questions
Does a higher market cap mean a better company?
It means the market assigns a larger equity value. Quality and valuation are separate questions. A wonderful business can be a small cap.
Why did market cap change more than the price?
Share issuance, buybacks, or a class of stock you are not looking at. Price and share count both count.