What Is an Option: Calls, Puts, and How They Work

Key Takeaways

• An option gives the buyer the right, not the obligation, to buy (call) or sell (put) an underlying at a fixed strike before expiration.
• Each US listed equity option covers 100 shares; a $3.00 quote costs $300 per contract, not $3.
• The most common beginner error is ignoring time decay: a long option loses value every day the underlying fails to move far enough.
• Options let investors shape payoffs, capping downside, leveraging upside, or hedging, in ways plain stock ownership cannot.

What It Is

There are two flavours of option, and every listed contract is one or the other. A call gives the buyer the right to buy the underlying at the strike price. A put gives the buyer the right to sell the underlying at the strike price.

Each US listed equity option contract covers 100 shares of the underlying stock. One AAPL call contract is a right over 100 shares, not one. Index options like SPX are cash-settled on a notional multiplier instead of delivering shares.

The contract has a fixed strike price, a fixed expiration date, and a market-determined premium that changes second by second while it trades.

The Intuition

A stock gives you linear exposure. If it goes up $1, you make $1 per share. If it falls $1, you lose $1. That symmetry is fine when you have a directional view, but it is inefficient when you want a specific shape of payoff.

Options let you shape the payoff. A long call costs a known premium and gives unlimited upside with the downside capped at what you paid. A long put is the mirror image: it pays off when the underlying falls, and the most you can lose is the premium. A seller of either option takes the opposite side, collecting premium up front in exchange for the obligation if the buyer exercises.

Informal option-like contracts have existed for centuries, but the modern standardised market dates to 1973. The Chicago Board Options Exchange listed the first standardised options that year, and Black and Scholes published their pricing formula in the same year. Together, those two events turned options from a bespoke dealer product into a liquid exchange-traded instrument.

How It Works

Every option contract has five core terms:

• Underlying asset. The stock, ETF, or index the option is written on.
• Type. Call or put.
• Strike price. The fixed price at which the buyer can buy (call) or sell (put) the underlying if exercised.
• Expiration date. The last day the contract is valid. US listed monthly options expire on the third Friday of the expiration month.
• Exercise style. American options can be exercised any time up to expiration. European options can only be exercised at expiration. Most US equity options are American. Index options such as SPX are European.

At expiration, only the relationship between the underlying price and the strike matters. For a call, the payoff is:

call payoff at expiry = max(underlying - strike, 0)

For a put:

put payoff at expiry = max(strike - underlying, 0)

Subtract the premium you paid (or add the premium you received, if you sold) to get the profit or loss per share. Multiply by 100 to get the dollar figure per contract for US equity options.

Worked Example

Suppose AAPL trades at $178. You buy one AAPL 180 call expiring in 30 days for $3.00 per share. The total cost is 3.00 x 100 = $300.

Three possible outcomes at expiration:

• AAPL closes at $190. The call is $10 in the money. Payoff is $10 per share, $1,000 per contract. Net profit is $1,000 - $300 = $700.
• AAPL closes at $180. The call is at the strike. Intrinsic value is zero. You lose the entire $300 premium.
• AAPL closes at $175. The call is out of the money. It expires worthless. You lose the full $300.

The seller of that call has the mirror outcome. They collected $300 up front. If AAPL rallies to $190, they owe $1,000 at exercise, a net loss of $700. A naked call seller's loss is theoretically unlimited because the underlying can keep rising.

Common Mistakes

1. Not distinguishing buyer from seller risk. A long call or long put risks only the premium paid. A short (written) call or put carries obligations that can dwarf the premium received, especially a naked short call where the underlying can rally indefinitely. The OCC's Characteristics and Risks of Standardized Options document exists precisely because the seller's risk profile is so different from the buyer's.

2. Forgetting the 100-share multiplier. A quote of "$3.00" on a US equity option means $3.00 per share. One contract represents 100 shares, so the dollar cost is $300, not $3. Traders who miss the multiplier size positions far too large or too small.

3. Ignoring time decay. A long option loses value every day the underlying does not move in its favour, even if nothing else changes. This decay, called theta, is the price of holding optionality. Beginners often buy cheap short-dated calls and watch the premium evaporate because they underestimated the decay rate.

4. Using "exercise" loosely. Most options are not exercised, they are closed by trading out of the position before expiration. Exercise is the formal act of converting the contract into a stock position (American style) or a cash settlement (European style). Closing a position is just selling the contract back into the market.

5. Confusing American and European style with geography. The style refers only to when the option can be exercised. An American-style option listed in London is still American. An SPX index option traded in Chicago is European. Style affects early-exercise risk, especially around dividends and corporate actions, not nationality.

Frequently Asked Questions

Q: What is an option in simple terms? An option is a contract that lets you buy or sell a stock at a set price before a deadline. You pay a premium for that right and are never forced to use it.

Q: How does knowing what an option is affect investment decisions? Recognizing that options separate the right to act from the obligation helps investors hedge positions, generate income, or take leveraged bets with capped downside.

Q: What is a real-world example of an option? Buying a 180-strike AAPL call for $3.00 gives you the right to purchase 100 shares at $180. If AAPL hits $190, the call is worth $10 intrinsic, a $700 profit on a $300 investment.

Q: How can investors use options without overexposing themselves? A practical rule of thumb: risk no more premium per trade than you would risk on the equivalent stock position, and treat the premium as the complete maximum loss.

Q: How is an option different from a futures contract? An option buyer is never obligated to transact; a futures buyer must settle at expiration. Options cost a premium for that flexibility; futures require margin but no upfront premium.

Sources

1. Cboe Options Institute. "Options 101." https://www.cboe.com/optionsinstitute/options_basics/options_101/
2. Options Clearing Corporation. "Characteristics and Risks of Standardized Options (June 2024 ODD)." https://www.theocc.com/company-information/documents-and-archives/options-disclosure-document
3. SEC Investor.gov. "Investor Bulletin: An Introduction to Options." https://www.investor.gov/introduction-investing/general-resources/news-alerts/alerts-bulletins/investor-bulletins-63
4. Black, F. and Scholes, M. (1973). "The Pricing of Options and Corporate Liabilities." Journal of Political Economy, 81(3), 637-654. https://www.cs.princeton.edu/courses/archive/fall09/cos323/papers/black_scholes73.pdf

Disclaimer

This article is educational content only and is not financial advice. Nothing here is a recommendation to buy, sell, or hold any security. Consult a licensed advisor before making investment decisions.