What Is an Option? A Beginner's Guide

New to this? Every unfamiliar term links to the options glossary. All numbers below are hypothetical.

Written by the MarketWrench team. Examples are worked with the same Black-Scholes model used in our calculators (4% rate, no dividends unless stated) and are reviewed for accuracy before publishing. How we create content.

An option is a contract about a stock's future price. It lets one person lock in a price today for a purchase or sale that might happen later, and it lets another person get paid for agreeing to that deal. Everything else in options trading is built from this one idea.

The one-sentence definition

An option gives its buyer the right, but not the obligation, to buy or sell 100 shares of a stock at a fixed price (the strike price) on or before a fixed date (the expiration). The buyer pays the seller a price for that right, called the premium.

Notice the asymmetry. The buyer has a right: they can use it or walk away. The seller has an obligation: if the buyer uses the right, the seller must follow through. The premium is what the seller charges for taking on that obligation.

An everyday analogy

Imagine a house you like is listed for $400,000. You pay the owner $5,000 for a written promise that you can buy the house for $400,000 any time in the next six months. If the neighborhood gets popular and the house is soon worth $450,000, you use your right, buy at $400,000, and you are ahead. If prices fall, you simply don't buy. You lose the $5,000, but nothing more. The owner keeps the $5,000 either way. That deposit agreement works very much like a call option.

Calls and puts

There are only two kinds of option, and every strategy on this site combines them:

A call is the right to buy 100 shares at the strike. Call buyers generally benefit when the stock rises.
A put is the right to sell 100 shares at the strike. Put buyers generally benefit when the stock falls, which is why puts are often used as insurance.

Each kind can be bought ("long") or sold ("short"), which gives four basic positions. Our calls vs puts guide walks through all four.

Why one contract means 100 shares

Standard US stock options cover 100 shares, called the contract multiplier. Prices are quoted per share, so a call quoted at $2.50 costs $2.50 × 100 = $250 for one contract. This trips up almost every beginner at least once: always multiply the quote by 100 to see the real money involved.

Worked example: buying a call HYPOTHETICAL

Hypothetical numbers only. Stock XYZ trades at $100. You buy one 30-day call with a $100 strike for $3.60, paying $360.

XYZ at expiration	What happens	Your P/L
$90	Buying at $100 makes no sense, so the call expires worthless	−$360
$100	Worth nothing at expiration	−$360
$103.60	Worth $3.60, exactly what you paid (the breakeven)	$0
$110	Worth $10 per share	+$640

The most you can lose is the $360 you paid. The person who sold you the call collected $360 up front, and their result is the mirror image of yours.

Worked example: buying a put as insurance HYPOTHETICAL

You own 100 shares of XYZ at $100 and worry about a drop. You buy a 30-day $95 put for $1.33 ($133). If XYZ falls to $80, you can still sell your shares for $95. Your loss is capped at $5 per share plus the $1.33 premium, or $633 total, instead of $2,000. If XYZ rises, the put expires and the $133 was the cost of protection. See the protective put guide.

Key words you will see everywhere

In the money (ITM): the option would be worth something if exercised right now. A call is ITM when the stock is above the strike.
Out of the money (OTM): exercising now would be pointless. A call is OTM when the stock is below the strike.
Intrinsic value: the ITM amount. Extrinsic value: everything else in the price, mostly time and volatility.
Exercise and assignment: the buyer exercises, and the seller is assigned. See assignment and early exercise.

Why people use options

Leverage: control 100 shares for a fraction of their price. Gains and losses are magnified in percentage terms.
Protection: put a floor under shares you own.
Income: sell options and collect premium, as in the covered call and cash-secured put.
Defined risk: spreads like the bull put spread set your maximum loss before you enter.

The risks, honestly

Bought options can and often do expire worthless, losing 100% of what was paid. Time works against buyers every day (see theta and time decay). Some sold options carry large or even unlimited risk. Options are not a shortcut to easy money. They are tools with trade-offs, and those trade-offs are what every page on this site tries to explain.

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FAQ

Do I have to buy the shares if I own a call?
No. As the buyer you have the right, not the obligation. Most traders sell the option to close it instead of exercising.

Why is the price quoted per share?
Convention. One standard contract covers 100 shares, so multiply the quote by 100 for the actual cost.

Can I lose more than I paid for an option?
Not as a buyer: the most you can lose is the premium. Sellers can lose more than they collect.

What happens if I do nothing at expiration?
Brokers generally exercise options that finish at least $0.01 in the money automatically, and OTM options expire worthless. Check your broker's rules.

Not financial advice

This page is for educational and informational purposes only. It is not financial, investment, tax, or legal advice, and it is not a recommendation to buy or sell any security or to use any strategy. All examples use hypothetical numbers. Options involve risk and are not suitable for everyone. Do your own research and consider talking to a licensed professional before trading.