What an option is and how it functions

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 own that right. The stock itself is called the underlying asset. If you never use the right, you lose only the premium you paid; you are not forced to complete the trade.

Options exist because they let you control a larger position with less money than buying the stock outright. If a stock costs $100 per share and you buy 100 shares, you spend $10,000. An option contract on that same stock might cost $200 to $500 total, giving you the right to buy or sell 100 shares. That leverage — controlling more shares with less cash — is why traders use options.

Every option has four core details: the stock it covers, the price at which you can buy or sell (called the strike price), the date the right expires (the expiration date), and whether it is a call or a put. These details are fixed when the contract is created and do not change.

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 own an option, and that is the maximum you can lose if the option expires worthless.
  • Options expire on a specific date, after which the contract no longer exists and you cannot use the right.
  • The strike price is the fixed price at which you can buy or sell the underlying stock if you choose to exercise the option.
  • Options are leveraged instruments, meaning you control more shares with less money than if you bought the stock directly.

Call options: the right to buy

A call option gives you the right to buy a stock at the strike price on or before the expiration date. You buy a call when you expect the stock price to rise. If the stock price climbs above the strike price, your call becomes more valuable because you can buy at the lower strike price and sell at the higher market price.

For example, suppose a stock trades at $50 today. You buy a call option with a strike price of $55, expiring in one month, and pay a $2 premium per share ($200 total for 100 shares). If the stock rises to $65 before expiration, your right to buy at $55 is now worth at least $10 per share — because you can exercise it, buy at $55, and when ready sell at $65. Your profit would be roughly $10 minus the $2 premium you paid, or $8 per share ($800 total).

If the stock never rises above $55, your call expires worthless. You lose the $200 premium and nothing more. You are never forced to buy the stock; you straightforward let the contract expire.

Put options: the right to sell

A put option gives you the right to sell a stock at the strike price on or before the expiration date. You buy a put when you expect the stock price to fall. If the stock price drops below the strike price, your put becomes more valuable because you can buy at the lower market price and sell at the higher strike price.

Suppose the same stock trades at $50 today. You buy a put option with a strike price of $45, expiring in one month, and pay a $2 premium per share ($200 total). If the stock falls to $35 before expiration, your right to sell at $45 is now worth at least $10 per share — because you can buy at $35 and exercise the put to sell at $45. Your profit would be roughly $10 minus the $2 premium, or $8 per share ($800 total).

If the stock never falls below $45, your put expires worthless and you lose the $200 premium. Like a call, you are never forced to sell; you straightforward let the contract expire.

Expiration dates and how time affects option value

Every option has a fixed expiration date. On that date, the contract ceases to exist. If you have not exercised the option by then, you lose the right forever. Most stock options expire on the third Friday of the month, though some brokers offer weekly expirations as well.

As the expiration date approaches, the option's value changes based on how far the stock price is from the strike price. An option that is "in the money" — meaning it would be profitable to exercise right now — is worth at least its intrinsic value (the difference between the stock price and the strike price). An option that is "out of the money" — meaning it would lose money to exercise — has value only if there is still time for the stock to move in your favor.

Time decay works against you as an option holder. Each day that passes, your option loses value if the stock price does not move. This is why options are short-term instruments: the closer you get to expiration, the less time remains for the stock to move in your favor, and the less the option is worth.

How option prices are set

An option's premium (the price you pay) depends on several factors. The most important are the stock price relative to the strike price, the time remaining until expiration, and how much the stock price typically moves (called volatility). A stock that swings wildly in price makes options more valuable because there is a greater chance the option will end up in the money.

Options are traded on exchanges just like stocks. The price changes throughout the trading day based on supply and demand. If many traders want to buy calls on a stock, the call premium rises. If many want to sell, it falls. You can close out an option before expiration by selling it to another trader, locking in a profit or loss without having to exercise it.

The bid-ask spread — the difference between what buyers will pay and what sellers will accept — is often wider for options than for stocks. This means you may pay more to buy and receive less when you sell, which cuts into your profit.

Exercising an option or letting it expire

When you own an option, you have two choices at any point before expiration: exercise it or let it expire. Exercising means using your right to buy (for a call) or sell (for a put) at the strike price. Letting it expire means the contract straightforward ends and you lose the premium you paid.

Most options are never exercised. Instead, traders buy and sell options to profit from price changes, then close the position before expiration. If you hold a call that is in the money, you can sell it to another trader for its current value rather than exercising it. This is often more profitable than exercising because you avoid transaction costs and the bid-ask spread on the underlying stock.

If you do exercise, your broker handles the mechanics. For a call, you pay the strike price and receive 100 shares (one option contract covers 100 shares). For a put, you deliver 100 shares and receive cash at the strike price. Some brokers charge a small fee for exercising.

Risk and leverage in options trading

Options are leveraged instruments, which means small price moves in the stock can create large percentage gains or losses in the option. If you buy a call for $200 and it becomes worth $800, that is a 300 percent gain on your $200 investment. But if the stock moves the wrong way, you can lose your entire $200 premium.

As an option buyer, your maximum loss is the premium you paid. You cannot lose more than that because you are not forced to exercise. However, if you sell options (a strategy called writing or selling short), your risk is much larger. A seller of a call option can lose far more than the premium received if the stock price rises sharply, because they are obligated to sell at the strike price if the buyer exercises.

Options are also sensitive to changes in volatility, interest rates, and the underlying stock's dividend. A sudden drop in volatility can wipe out the value of an option even if the stock price does not move. This is why options are considered riskier and more complex than buying stocks directly.

Frequently Asked Questions

What happens if I own a call option and the stock price stays below the strike price?

The option expires worthless and you lose the premium you paid. You are never forced to buy the stock at the strike price. Your loss is limited to the amount you spent on the option.

Can I sell an option before the expiration date?

Yes. Options are traded on exchanges throughout the day, so you can sell your option to another trader at any time before expiration. This is how most option traders close their positions and lock in profits or losses.

What is the difference between American and European options?

American options can be exercised at any time up to and including the expiration date. European options can only be exercised on the expiration date itself. Most stock options traded in the United States are American-style, which gives you more flexibility.

How much money do I need to start trading options?

Your broker sets a minimum account balance, which varies. Many brokers require $2,000 to $25,000 to trade options. Some also require you to pass a knowledge test or have prior trading experience. Check your broker's requirements before opening an account.

Why would I buy a put option if I already own the stock?

Buying a put on a stock you own is called a protective put. It limits your downside if the stock price falls while letting you keep the upside if it rises. You pay the put premium as insurance, similar to buying homeowner's insurance.