What option trading is

Option trading is buying and selling contracts that give you the right—but not the obligation—to buy or sell a stock at a set price by a certain date. You do not own the stock itself. Instead, you own a contract that lets you control 100 shares of a stock for a fraction of what those shares would cost outright. The contract has an expiration date, and after that date it becomes worthless if you have not used it.

The two basic types are call options (the right to buy) and put options (the right to sell). A call option makes money when the stock price goes up. A put option makes money when the stock price goes down. You can buy these contracts hoping the price moves in your favor, or you can sell them to someone else and collect a payment upfront.

Option trading happens on exchanges like the Chicago Board Options Exchange (CBOE). Prices change throughout the trading day based on what buyers and sellers agree to pay. Unlike stocks, which represent ownership, options are time-limited bets on price movement.

Key Takeaways

  • An option contract gives you the right to buy (call) or sell (put) 100 shares of a stock at a locked-in price before the expiration date.
  • You pay a premium upfront to buy an option, and that premium is the most you can lose if the trade goes against you.
  • Options expire on a specific date, usually the third Friday of each month, and become worthless if you do not use them by then.
  • Option prices move based on the stock price, time remaining, and how much the stock price is expected to swing in the future.
  • Selling options (called writing) collects money upfront but exposes you to larger losses than buying options does.

How the mechanics work: buying a call option

Say Apple stock trades at $150 per share. You buy a call option that gives you the right to buy Apple at $155 per share anytime before the third Friday of next month. You pay $3 per share for this right, which means $300 total (because one contract covers 100 shares). This $300 is called the premium.

If Apple stock rises to $170 before expiration, your contract is now worth money. You can exercise it (buy 100 shares at $155) and immediately sell them at $170, pocketing $15 per share minus the $3 premium you paid—a $12 profit per share, or $1,200 total. Or you can sell the contract itself to someone else for whatever it is worth at that moment.

If Apple stock stays at $150 or falls, your contract loses value. If it is still at $150 at expiration, the contract expires worthless and you lose the $300 premium. That $300 is your maximum loss on a bought call option. You never have to buy the stock if you do not want to.

How the mechanics work: buying a put option

A put option works in reverse. Say Microsoft stock trades at $400 per share. You buy a put option that gives you the right to sell Microsoft at $390 per share before expiration. You pay $5 per share ($500 total) for this right.

If Microsoft stock falls to $370, your put option is now worth money. You can exercise it (sell 100 shares at $390, even though the market price is $370) or sell the contract itself. If the stock stays above $390 or rises, the put expires worthless and you lose your $500 premium.

Put options are often used as insurance. If you own 100 shares of Microsoft and you are worried the price might drop, you can buy a put option to lock in a selling price. If the stock crashes, your put protects you. If the stock rises, you let the put expire and keep your shares.

Selling options (writing) and the risks

Instead of buying an option, you can sell one. When you sell a call option, you collect the premium upfront—say $300—but you are now obligated to sell 100 shares at the strike price if the buyer exercises the contract. When you sell a put option, you collect the premium but are obligated to buy 100 shares at the strike price if the buyer exercises.

Selling options sounds like assistance programs because you collect cash immediately. But the risk is much larger than buying. If you sell a call option on Apple at $155 and the stock shoots to $200, you must sell 100 shares at $155 even though they are worth $200. You lose $45 per share ($4,500 total) minus the premium you collected. If you sell a put option and the stock crashes, you must buy 100 shares at a price far above what they are now worth.

Buying an option limits your loss to the premium you paid. Selling an option can cost you far more than the premium you collected. Most traders who sell options use strategies to limit that risk, such as owning the stock already or selling options only on stocks they are willing to own.

What moves an option's price

An option's price (premium) is not just the difference between the stock price and the strike price. Four main factors move it:

  • Stock price movement: A call option becomes more valuable when the stock rises and less valuable when it falls. A put option becomes more valuable when the stock falls and less valuable when it rises.
  • Time decay: As the expiration date gets closer, an option loses value even if the stock price does not move. On the expiration date itself, an option is worth only the difference between the stock price and the strike price (or zero if that difference is negative).
  • Implied volatility: This is how much traders expect the stock price to swing in the future. If traders expect big price swings, options cost more because there is a bigger chance the option will end up in the money. If traders expect the stock to barely move, options cost less.
  • Interest rates: Rising interest rates make call options slightly more expensive and put options slightly cheaper, though this effect is usually small.

The difference between in-the-money and out-of-the-money

An option is in-the-money when it has intrinsic value—meaning you could exercise it right now and make money. A call option is in-the-money when the stock price is above the strike price. A put option is in-the-money when the stock price is below the strike price.

An option is out-of-the-money when exercising it would lose money. A call option is out-of-the-money when the stock price is below the strike price. A put option is out-of-the-money when the stock price is above the strike price. Out-of-the-money options are cheaper because they have no intrinsic value—they are pure bets on future price movement.

An option is at-the-money when the stock price equals the strike price. These options have no intrinsic value but are often the most sensitive to price changes.

Expiration dates and how they work

Most stock options expire on the third Friday of each month. Some expire weekly (on Fridays), and some expire daily. The expiration date is the last day you can exercise the option. After the market closes on that day, any option that is out-of-the-money becomes worthless instantly.

If your option is in-the-money at expiration and you hold it in a brokerage account, most brokers will automatically exercise it for you. If you hold a call option that is $5 in-the-money, your broker will buy 100 shares at the strike price. If you hold a put option that is $5 in-the-money, your broker will sell 100 shares at the strike price. You can also choose to close the position before expiration by selling the contract.

Time decay accelerates as expiration approaches. An option that is far from expiration loses value slowly. An option that expires in a few days loses value much faster, even if the stock price does not move. This is why options are sometimes called wasting assets.

Frequently Asked Questions

Do I have to own the stock to buy an option?

No. You can buy a call option on any stock without owning it. You are simply buying the right to purchase it at a set price. You do not have to exercise the option—you can sell it to someone else or let it expire.

What happens if I do not have enough money to exercise an option?

If you own a call option and want to exercise it, you need cash to buy 100 shares at the strike price. If you do not have the cash, you can sell the option contract instead and keep the profit. Most brokers will not let you exercise a call unless you have the money available.

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

If you bought the option, no. Your maximum loss is the premium you paid. If you sold the option, yes—your loss can be much larger than the premium you collected. This is why selling options is riskier than buying them.

What is the difference between American and European options?

American options can be exercised anytime before expiration. European options can only be exercised on the expiration date itself. Most stock options traded in the U.S. are American. European options are less common and usually trade on indexes rather than individual stocks.

How do I know what strike price to choose?

Strike price depends on your outlook and risk tolerance. A strike price closer to the current stock price costs more but has a better chance of making money. A strike price far from the current stock price costs less but requires a bigger price move to make money. There is no single right answer—it depends on how much you want to risk and how much you expect the stock to move.