Stock option trading is a contract that gives you the right to buy or sell a specific stock at a set price by a certain date

When you trade a stock option, you are not buying the stock itself. You are buying a contract — a legal agreement between you and another trader. That contract says you have the right (but not the obligation) to buy or sell 100 shares of a particular stock at a price you agree on now, before a date that is already set.

The price you agree on now is called the strike price. The date by which you must use that right is called the expiration date. You pay money upfront for this contract, called the premium. That premium is the price of the option itself — not the price of the stock.

There are two types of options. A call option gives you the right to buy the stock. A put option gives you the right to sell the stock. Most people who trade options are betting on whether the stock price will go up or down by the expiration date, not planning to actually buy or sell 100 shares.

Key Takeaways

  • An option contract controls 100 shares of stock but costs far less than buying those shares outright, which is why traders use options to bet on price movement with smaller amounts of money.
  • A call option profits if the stock price rises above the strike price plus the premium you paid; a put option profits if the stock price falls below the strike price minus the premium you paid.
  • Options expire on a set date — usually the third Friday of the month — and become worthless if you do not sell or exercise them before that date.
  • Most option traders close their position by selling the contract to another trader before expiration, rather than actually buying or selling the underlying stock.

How the premium price works and why options cost less than stock

The premium is what you pay to own the option contract. It is quoted per share, but one option contract always controls 100 shares, so you multiply the quoted price by 100 to get the total cost. If a call option has a premium of $2, you pay $200 to own that contract.

Options cost less than the stock because you are not buying the stock — you are buying the right to buy it at a fixed price later. If a stock trades at $50 per share, buying 100 shares costs $5,000. A call option on that stock might cost $200 to $400, depending on how far away the strike price is and how much time is left before expiration. This is why options are called leverage: you control the same 100 shares with a much smaller amount of money.

The premium changes every day as the stock price moves and as the expiration date gets closer. If you buy a call option and the stock price rises, the premium usually rises too, so you can sell the contract for more than you paid. If the stock price falls, the premium falls, and you lose money if you sell.

Call options: profiting when you think the stock will rise

A call option gives you the right to buy 100 shares at the strike price. You profit if the stock price rises above the strike price plus the premium you paid.

Example: You buy a call option with a strike price of $50 and pay a $2 premium ($200 total). The stock is currently trading at $50. If the stock rises to $55 before expiration, your option is now worth at least $5 per share ($500 total), because you have the right to buy at $50 and sell at $55. You can sell that contract to another trader and pocket the difference. Your profit is $300 ($500 minus the $200 you paid).

If the stock stays at $50 or falls below $50, your option loses value. If the stock is still at $50 on expiration day, your option expires worthless because there is no advantage to buying at $50 when you can buy in the market at $50. You lose the entire $200 premium.

Put options: profiting when you think the stock will fall

A put option gives you the right to sell 100 shares at the strike price. You profit if the stock price falls below the strike price minus the premium you paid.

Example: You buy a put option with a strike price of $50 and pay a $2 premium ($200 total). The stock is currently trading at $50. If the stock falls to $45 before expiration, your option is now worth at least $5 per share ($500 total), because you have the right to sell at $50 when the market price is $45. You can sell that contract and pocket the difference. Your profit is $300.

If the stock stays at $50 or rises, your option loses value. If the stock is at $50 on expiration day, your option expires worthless because there is no advantage to selling at $50 when you can sell in the market at $50. You lose the $200 premium.

Expiration dates and why time matters

Every option has an expiration date. For stock options, this is almost always the third Friday of the month. After that date, the contract no longer exists and you cannot use it.

Time decay works against you if you own an option. As the expiration date gets closer, the premium shrinks even if the stock price does not move. An option that is far from expiration and slightly out of the money might still have value because there is time for the stock to move. The same option two days before expiration might be worthless.

This is why most option traders close their position before expiration by selling the contract to another trader. They do not wait until the last day and they do not actually exercise the option to buy or sell the stock. They buy the contract, the stock moves in their favor, the premium rises, and they sell it for a profit.

In-the-money and out-of-the-money options

An option is in-the-money if it would make money if you exercised it right now. A call option is in-the-money if the stock price is above the strike price. A put option is in-the-money if the stock price is below the strike price.

An option is out-of-the-money if it would lose money if you exercised it right now. A call option is out-of-the-money if the stock price is below the strike price. A put option is out-of-the-money if the stock price is above the strike price.

An option is at-the-money if the stock price is exactly at the strike price. This is rare because stock prices move in cents.

Out-of-the-money options are cheaper because they have no intrinsic value — they are pure bets that the stock will move far enough before expiration. In-the-money options cost more because they already have value built in. A trader who buys an out-of-the-money option needs the stock to move more to make a profit, but the bet costs less upfront.

How option prices change and what affects the premium

The premium you pay for an option depends on several things. The stock price is the most obvious: if the stock rises, call premiums rise and put premiums fall. But the premium also depends on how much time is left until expiration, how volatile the stock is, and how far away the strike price is from the current stock price.

Options on stocks that move a lot (high volatility) cost more because there is a bigger chance the option will end up in-the-money. Options on stable stocks cost less. Options with more time until expiration cost more because there is more time for the stock to move. Options that are far out-of-the-money cost less because the stock has to move a long way for them to become profitable.

The bid-ask spread also matters. The bid is what another trader will pay you for the option; the ask is what you have to pay to buy it. If you buy at the ask and sell at the bid, you lose money on the spread alone, even if the stock moves in your favor. Options on popular stocks have tighter spreads because more traders are buying and selling them.

Frequently Asked Questions

What happens if I do not sell my option before expiration?

If your option is in-the-money on expiration day, most brokers will automatically exercise it for you — they will buy or sell the 100 shares at the strike price. If your option is out-of-the-money, it expires worthless and you lose the premium you paid. You can also choose to close the position yourself by selling the contract before expiration.

Can I actually buy the stock using a call option instead of buying it outright?

Yes, you can exercise the option and buy 100 shares at the strike price. But most traders do not do this. They sell the option contract to another trader instead, which is faster and does not require you to have the cash to buy the shares. Exercising is more common for traders who actually want to own the stock.

What is the maximum amount I can lose on an option?

The maximum loss on an option you buy is the premium you paid. If you buy a call or put and the stock moves the wrong way, the option expires worthless and you lose 100 percent of your investment. You cannot lose more than that because you are not obligated to exercise the option.

Why do some options cost more than others if they control the same 100 shares?

Options on the same stock but with different strike prices or expiration dates cost different amounts. An option that is closer to being in-the-money costs more. An option with more time until expiration costs more. An option on a volatile stock costs more than an option on a stable stock.

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

No. When you sell a put option, you are betting the stock will stay above the strike price. If it falls below the strike price and the buyer exercises, you are obligated to buy 100 shares at the strike price. You need enough cash in your account to cover that purchase, but you do not need to own the stock beforehand.