What an option is and why traders use them

An option is a contract that gives you the right—but not the obligation—to buy or sell a specific stock at a set price by a certain date. You pay a fee upfront, called the premium, to hold that right. The person or firm on the other side of the contract collects that premium and takes on the obligation to sell or buy if you decide to exercise your right.

Traders use options for two main reasons: to bet on whether a stock price will go up or down without owning the stock itself, or to protect a stock they already own against a price drop. Because options cost less than buying the stock outright, a small amount of money can control a larger position. That leverage cuts both ways—you can make more money on a smaller investment, but you can also lose your entire premium if the price moves the wrong way.

Key Takeaways

  • A call option gives you the right to buy a stock at a set price; a put option gives you the right to sell a stock at a set price.
  • You pay a premium upfront to buy an option, and that is the most you can lose if the trade goes against you.
  • The set price is called the strike price, and the deadline to use your right is called the expiration date.
  • Options are leveraged instruments—a small premium controls a larger stock position, which means bigger gains or losses on your money.

Calls and puts: the two types of options

A call option is the right to buy a stock at a set price (the strike price) before the expiration date. You buy a call when you think the stock price will rise. If the price goes above the strike price, you can buy at the lower strike price and sell at the higher market price, or simply sell the option itself for a profit. If the price stays below the strike price, the option expires worthless and you lose the premium you paid.

A put option is the right to sell a stock at a set price before the expiration date. You buy a put when you think the stock price will fall. If the price drops below the strike price, you can sell at the higher strike price and buy at the lower market price, or sell the option for a profit. If the price stays above the strike price, the put expires worthless and you lose the premium.

You can also be on the other side: selling a call (called "writing" a call) or selling a put. When you sell an option, you collect the premium upfront but take on the obligation to buy or sell if the buyer exercises. This is riskier because your potential loss is not capped the way a buyer's loss is.

Strike price, expiration date, and how they affect the premium

The strike price is the price at which you have the right to buy (for a call) or sell (for a put). It stays the same for the life of the contract. The expiration date is the last day you can exercise your right; after that, the option is worthless.

The premium you pay depends on several factors. The closer the strike price is to the current stock price, the higher the premium, because the option has a better chance of being profitable. The longer the time until expiration, the higher the premium, because there is more time for the stock price to move in your favor. If the stock is volatile—meaning its price swings widely—the premium is also higher, because big moves are more likely.

An option is "in the money" when it would be profitable to exercise right now. For a call, that means the stock price is above the strike price. For a put, it means the stock price is below the strike price. An option is "out of the money" when exercising would lose money. An option is "at the money" when the stock price equals the strike price.

How exercising an option works

When you own a call option and the stock price rises above the strike price, you can exercise—meaning you buy 100 shares of the stock at the strike price. (One option contract always covers 100 shares.) You can then hold those shares, sell them immediately for a profit, or do nothing and let the option expire.

When you own a put option and the stock price falls below the strike price, you can exercise to sell 100 shares at the strike price. You can sell shares you already own, or in some cases sell shares you do not own (called a short sale), depending on your account type and broker rules.

Most traders never exercise. Instead, they buy and sell options contracts themselves, the same way they buy and sell stocks. If you bought a call for $2 per share and the option is now worth $5 per share, you can sell it and pocket the $3 difference, without ever owning the stock.

American and European options: when you can exercise

American options can be exercised any time before the expiration date. European options can only be exercised on the expiration date itself. Most options traded in the United States are American, which gives you more flexibility. European options are less common in retail trading but do exist for some stocks and indexes.

This difference matters because it affects the premium. American options cost more because you have the freedom to exercise whenever you want. European options cost less because you are locked into the expiration date.

Why options are riskier than owning stock

When you buy a stock, your loss is capped at what you paid—if the stock goes to zero, you lose 100 percent. When you buy an option, your loss is also capped at the premium you paid, which is usually much less than the stock price. That sounds safer, but the risk is different.

An option loses value as the expiration date approaches, even if the stock price does not move. This is called time decay. If you buy a call for $3 and the stock price stays flat, the option might be worth only $1 a week before expiration. You lose $2 even though nothing changed.

Options also move faster than stocks. If a stock rises 5 percent, an option on that stock might rise 20 percent or fall 20 percent, depending on the strike price and how much time is left. This leverage works in your favor when you are right and against you when you are wrong. Most options expire worthless, meaning the buyer loses the entire premium.

Frequently Asked Questions

What does it mean when an option is "in the money"?

An option is in the money when exercising it would make money right now. For a call, the stock price is above the strike price. For a put, the stock price is below the strike price. In-the-money options have real value and are more expensive to buy.

Can I lose more money than I paid for the option?

If you bought the option, no—your loss is capped at the premium you paid. If you sold (wrote) the option, yes—your loss can be much larger, especially if you sold a call on a stock that rises sharply. This is why selling options is riskier than buying them.

What happens to my option on the expiration date?

If the option is in the money, most brokers automatically exercise it for you. If it is out of the money, it expires worthless and you lose the premium. You can also manually exercise or sell the option before expiration if you want to close the position early.

Do I need to own the stock to buy a put option?

No. You can buy a put on any stock, whether you own it or not. If you exercise, you can sell shares you own, or you can short-sell shares you do not own (if your broker and account type allow it). Many traders buy puts on stocks they do not own as a bet that the price will fall.

Why do options expire?

Options have expiration dates because they are time-limited contracts. The seller (writer) of the option needs to know when their obligation ends. Expiration dates range from days to months to years, depending on the type of option. After expiration, the contract no longer exists.