To know how many shares of stock you have, you can generally check your brokerage statements or the brokerage website. The number of shares you own may change as you trade stock, but it can also change due to a variety of events initiated by the companies in which you're investing.
TL;DR (Too Long; Didn't Read)
You can contact your broker, check your brokerage statements or visit their website to find out the number of stock shares you have. Do know that the number can change, so you may want to check it from time to time.
Check With Your Broker
Ordinarily, you can visit your broker's website or smartphone app or give the company a call to find out what stock you own, how many shares you have of each and how much they're worth. If you receive paper statements, this information should be outlined there as well. Generally, you'll also see the cost basis for the shares, including how much you paid for them.
If you work with multiple brokers, you may want to check with each of them to know your complete holdings. You may indirectly own stock through a pension plan or through mutual funds or index funds that invest in the stock market, though these aren't shares that you can buy or sell directly.
Why Numbers Could Change
Naturally, the amount of shares of any particular stock you own will change if you buy or sell stock. But these numbers can also change due to corporate actions initiated by the company in which you've invested. For instance, a company can undergo a stock split, where each share is replaced by a different, larger number of shares; in a two-for-one split, the number of shares every investor owns doubles. Stock splits are sometimes done to lower the price of individual shares and make them more accessible to small investors.
Companies can also buy stock back from investors, in which case some of your shares may be replaced by cash in your brokerage account. Alternatively, they can pay out cash dividends, providing a certain amount of money to each investor depending on how many shares he owns.
If you have told your broker to reinvest your dividends, the company will automatically use that money to buy more of the same stock, so a dividend will cause you to own more shares. In some cases, you can even end up owning fractional numbers of shares in the company this way.
Mergers and Acquisitions
When two companies merge or one buys another, one will sometimes trade its stock for some or all of the stock of the other. In other cases, one company may buy all the stock of the other or trade a mix of cash and stock.
In any of these events, some of your stock may be replaced by cash, stock in an entirely different company or a combination of the two. If you do receive cash, you may owe tax as if you had sold your stock.
Steven Melendez is an independent journalist with a background in technology and business. He has written for a variety of business publications including Fast Company, the Wall Street Journal, Innovation Leader and Ad Age. He was awarded the Knight Foundation scholarship to Northwestern University's Medill School of Journalism.