Options basics: how calls and puts work, with payoff diagrams

An option is a contract that gives its buyer a choice. A call option gives the right to buy a stock at a fixed price before a deadline. A put option gives the right to sell a stock at a fixed price before a deadline. The buyer pays for that choice up front, and the seller of the option takes the cash in exchange for standing ready to do the other side of the deal if asked.

That small idea underpins a large market. Options let people hedge a portfolio, earn income on shares they already own, bet on a move with a limited loss, or take on risk that can cost far more than they put in. The same contract can be a cautious tool in one account and a dangerous one in another, depending on which side you are on and how much of it you hold.

This guide covers the building blocks: calls and puts, the 100-share contract, strike price, expiration and premium, what buyers and sellers are each entitled to and on the hook for, American versus European exercise, the clearinghouse that stands behind every US listed option, the disclosure document every broker must hand you, and how to read the payoff diagrams the rest of this library uses. Every number here is illustrative.

What an option is

An option is a derivative: its value comes from something else, called the underlying. For the options most individual investors meet, the underlying is a stock or an exchange-traded fund (ETF), such as Apple shares or the SPDR S&P 500 ETF. There are also options on stock indexes, on futures and on currencies, but the mechanics below are the same.

Every listed option is defined by four things:

The fifth number, the premium, is not part of the contract's definition. It is the market price of the option, set by buyers and sellers on the exchanges, and it changes every second the market is open, just like a share price.

Calls and puts in plain terms

Think of a call as a reservation to buy. You pay a non-refundable fee today to lock in a purchase price. If the stock later trades well above that price, the reservation is valuable, because it lets you buy below the market. If the stock stays below it, you let the reservation lapse, and all you have lost is the fee.

Think of a put as insurance on a price. You pay a fee today for the right to sell at a set price. If the stock collapses, the right to sell at the old, higher price is valuable. If the stock rises, you never use it, and the fee was the cost of protection.

That analogy breaks down in one important way. With a real insurance policy you are dealing with a company that has reserves. With an option, someone in the market is on the other side: the seller, also called the writer. Every option that is bought was sold by somebody, and that person has taken on an obligation.

The contract: 100 shares, a strike, an expiration

A standard US equity option covers 100 shares of the underlying. Option prices are quoted per share, so you multiply by 100 to get the cost of one contract. This multiplier is the single most common source of beginner confusion.

Strikes are listed at set intervals around the current share price, for example every $1, $2.50 or $5 depending on the stock and how far the strike is from the price. Many expirations are listed at once: standard monthly options expire on the third Friday of the month, and heavily traded underlyings also have weekly expirations, and in some cases daily ones. Each combination of underlying, type, strike and expiration is a separate contract with its own price, volume and open interest. The full list for one underlying is its option chain.

When a company splits its stock, pays an unusual special dividend or is acquired, the OCC adjusts the affected contracts so the holder's position keeps its economic value. An adjusted contract can cover something other than 100 shares, which is worth checking before trading one.

How a contract is named

Brokers and data feeds identify each contract with a standardized symbol that packs the four terms together: the underlying's root symbol, the expiration date as year, month and day, a C or P, and the strike. A $100 XYZ call expiring December 18, 2026 would be written along the lines of XYZ261218C00100000, where the last eight digits are the strike times 1,000. You rarely need to type one, but it explains the long codes you see on statements.

Buyers and sellers: rights versus obligations

Every option has two sides, and they are not mirror images in what they risk. The buyer holds a right; the seller carries a duty.

The buyer (holder, or "long") pays the premium. In return they may exercise: buy the shares at the strike for a call, or sell them at the strike for a put. They are never required to. If exercising makes no sense, the buyer lets the option expire, and the most they can lose is the premium they paid.

The seller (writer, or "short") receives the premium the moment the trade is done. In return, if a buyer exercises, the OCC assigns that exercise to someone who is short the same contract, and the assigned seller must perform: deliver 100 shares at the strike for a call, or buy 100 shares at the strike for a put. The seller does not get to choose whether that happens.

What each side can make or lose follows directly:

A seller who already owns the shares behind a short call is covered: if assigned, they hand over shares they already hold, so the loss is the gain they gave up, not an open-ended bill. A seller who does not own the shares is uncovered or naked, and must buy them in the market at whatever the price is. Because the price of a stock has no ceiling, FINRA describes the potential loss on an uncovered call as theoretically unlimited.

Most option positions never reach exercise. Buyers and sellers usually close their positions before expiration by doing the opposite trade: a buyer sells the same contract back to the market, and a seller buys it back. The difference between the opening and closing prices is the profit or loss.

Payoff diagrams: the picture of an option at expiration

A payoff diagram shows what a position is worth, or how much it has made or lost, at expiration across a range of possible stock prices. It is the standard way to see an option's shape at a glance. The horizontal axis is the stock price on expiration day. The vertical axis is profit or loss per share, after the premium.

At expiration an option is worth only what exercise would deliver:

The call

The diagram shows the defining features of a long call. The loss is flat and capped at the premium on the left. The line bends at the strike and rises one dollar for every dollar the stock climbs above it. The break-even sits to the right of the strike by exactly the premium. For the seller, the shape flips: a capped gain on the left and a loss that grows without limit on the right.

The put

Two caveats apply to every payoff diagram. First, it describes expiration only. Before then, an option also carries time value, so its price curve is smooth rather than kinked; Option premium and time value: decay, volatility and Black-Scholes shows that curve. Second, it ignores commissions, fees, taxes and the interest you might have earned on the cash, all of which shift real results.

What sets the premium

The premium has two parts. Intrinsic value is what the option would be worth if exercised immediately: for a call, how far the stock is above the strike; for a put, how far it is below. Time value (also called extrinsic value) is everything else: the price of the chance that the option becomes more valuable before it expires. Option moneyness: in, at and out of the money explained works through both with tables.

Time value depends mainly on three things:

• Time to expiration. More time means more chances for a large move, so longer-dated options cost more. Time value shrinks every day and falls fastest near the end.
• Volatility. A stock that swings widely is more likely to move far past the strike, so its options are dearer. The volatility that is built into an option's market price is called implied volatility, and it is the main thing option traders argue about.
• Interest rates and dividends. Smaller effects. Higher rates nudge call prices up and put prices down; an expected dividend does the reverse.

Pricing models, the best known of which is Black-Scholes, turn those inputs into a theoretical premium. The sensitivity of the premium to each input has a Greek-letter name (delta, gamma, theta, vega, rho), covered in Option Greeks: delta, gamma, theta, vega and rho with examples.

American versus European exercise

The exercise style says when the holder can use the right.

• American-style options can be exercised on any business day up to and including the expiration date. As of 2026, options on individual US stocks and ETFs are American-style.
• European-style options can be exercised only at expiration. Many US index options are European-style. Cboe's S&P 500 index options (SPX), for example, can only be exercised at expiration and settle in cash, with a $100 multiplier, instead of delivering shares.

The style matters mostly to sellers. A seller of an American-style option can be assigned at any time before expiration, not only on the last day. In practice early exercise is uncommon, because exercising throws away whatever time value the option has left, and the holder would usually do better selling the option. It does happen in predictable situations, especially for calls just before a stock goes ex-dividend. Option exercise and assignment: how it works and when it happens covers when and why.

Settlement is the other half of the story. Stock and ETF options are physically settled: exercise means real shares change hands. Cash-settled index options pay the difference between the strike and the index's settlement value, and no shares move.

The Options Clearing Corporation

When you buy an option on a US exchange, you do not end up with a contract against the person who happened to sell it. The Options Clearing Corporation (OCC) steps in between. It is the issuer of every US exchange-listed option and the guarantor that the obligations behind them will be met.

This arrangement does three useful things:

1. It removes counterparty risk for individuals. If the original seller goes broke, the OCC still stands behind your contract, backed by the margin and clearing funds its member firms post.
2. It makes contracts interchangeable. Every $100 XYZ call for a given expiration is identical, so you can buy one from one person and sell it later to someone else on any exchange that lists it. That is what lets positions be closed before expiration.
3. It runs exercise and assignment. Exercise notices go to the OCC, which assigns them to clearing firms with short positions in that contract using a random procedure. The firms then pass the assignment to a specific customer account.

The OCC is regulated by the Securities and Exchange Commission (SEC) and, for its futures business, the Commodity Futures Trading Commission (CFTC). It does not protect you from investment losses; it only makes sure the contract is honored.

The Options Disclosure Document

Before your first options trade, US federal securities rules require your broker to give you a booklet titled Characteristics and Risks of Standardized Options, usually called the Options Disclosure Document (ODD). The OCC administers it, and it is available free on the OCC's website.

As of 2026, FINRA Rule 2360 requires the broker to deliver the current ODD at or before the time your account is approved for options trading, and to send any amendments before you trade the affected kind of option. The document explains how listed options work, how exercise and settlement happen for each type, and the specific risks of buying, writing, spreading and trading options on margin.

It is long and dry, and few people read it end to end. It is still worth reading the sections on the kind of option you plan to trade, because it is the regulator-approved statement of what can go wrong.

Getting approved to trade options

You cannot simply start buying options in a new brokerage account. As of 2026, FINRA Rule 2360 bars a broker from accepting an options order until a qualified principal has specifically approved the account in writing. To decide, the firm must seek information such as your investment objectives, income, net worth, liquid net worth, age and investment experience.

Brokers grant approval at a level or tier. Each firm sets its own ladder, but the lowest level usually allows only covered calls and cash-secured puts, a middle level adds buying calls and puts and then spreads, and the highest level adds uncovered selling. Options risks and approval levels: what brokers check and why describes the ladder and why it exists.

Why people use options

There are three broad reasons, and each has a mirror-image risk.

To limit or shape risk. Someone who owns shares can buy a put as a floor under a position, paying the premium as the cost of protection. Someone who wants exposure to a rally can buy a call and know their maximum loss in advance, rather than buying the shares outright.

To earn premium. Someone who owns shares can sell calls against them and collect premium, giving up gains above the strike. Someone willing to buy a stock at a lower price can sell a put and be paid while they wait. The pages on Covered calls: how they work, payoff, and assignment risk and Cash-secured puts: mechanics, payoff and the obligation to buy work through both.

To speculate with leverage. A call that costs $4 a share can return 275% when the stock rises 15%, as in the example above. The same call loses 100% when the stock merely stays flat. Leverage magnifies both directions, and options run out of time.

Combining options into spreads gives positions with a defined maximum gain and loss. The Vertical spreads: bull call, bear put and credit spreads explained page shows the most common family.

Common pitfalls

Forgetting the multiplier. A $0.50 option costs $50 per contract, and a $15 option costs $1,500. Order sizes add up faster than people expect.

Being right but too late. An option buyer needs the move to happen before expiration, and by enough to cover the premium. A stock that rises 5% the week after your call expires does nothing for you.

Ignoring the spread. Many contracts, especially far from the stock price or far in the future, trade with wide gaps between bid and ask. Buying at the ask and selling at the bid can cost a meaningful share of the premium on a round trip.

Treating a short option as income without a ceiling on loss. Selling options collects small, frequent gains and occasionally suffers large losses. An uncovered call has no upper limit on its loss.

Losing track of expiration. Brokers and the OCC will automatically exercise most in-the-money options at expiration. An option you forgot about can turn into 100 shares of stock, or a 100-share short position, on Monday morning.

Options compared with owning the stock

How Finabase shows options

Finabase is a research app: it shows option data, and it does not take orders or hold accounts. Its options page opens the chain for any optionable US stock or ETF, with shortcuts for popular underlyings such as SPY.

Each chain page, for example AAPL options, uses the classic straddle layout: calls on the left, the strike column in the middle and puts on the right. For each contract it lists the bid, ask, last price, percentage change, volume, open interest and implied volatility. A row of chips switches between every listed expiration, and a second row sets how many strikes to show on each side of the current price (5, 10, 20, 50 or all). In-the-money cells are tinted and the current underlying price is shown, so you can see at a glance which strikes have intrinsic value. Signed-in users can star contracts to watch them; the watched list on the options page shows their latest quotes, refreshes while the page is open, and exports to CSV. Provider quotes may be delayed.

Frequently asked questions

How much money do you need to trade options?

Buying one option costs its premium times 100, so a contract quoted at $1.20 costs $120 plus fees. That low entry price is part of the appeal and part of the danger. Selling options usually requires much more, because the broker holds cash or margin against the obligation: a cash-secured put on a $50 strike ties up $5,000.

Can you lose more than you invest with options?

As a buyer, no: the most you can lose is the premium you paid. As a seller, yes. An uncovered call has theoretically unlimited loss, and an uncovered put can lose up to the strike times 100, minus the premium, if the stock goes to zero.

Do you have to exercise an option to make money?

No. Most option traders close their positions by selling the option back to the market before expiration. Selling captures any remaining time value, which exercising throws away.

What happens if I hold an option until expiration?

If it is in the money by at least $0.01 at the close on expiration day, it will generally be exercised automatically unless you or your broker instruct otherwise. If it is out of the money, it expires worthless. Brokers may also close positions themselves if you cannot afford the resulting stock trade.

Are options the same as employee stock options?

No. Employee stock options are granted by a company to its staff under its own plan rules, cannot usually be traded, and are created by the company itself. Listed options are standardized exchange-traded contracts issued by the OCC and traded between investors.

Summary

A call is a right to buy and a put is a right to sell, each at a fixed strike until an expiration date, and one standard US contract covers 100 shares. Buyers pay a premium for the right and can lose only that premium; sellers collect it and take on an obligation that can cost far more. Payoff diagrams show those shapes at expiration, while time value, volatility and the passage of time govern prices before it. Every US listed option is issued and guaranteed by the OCC, every broker must give you the Options Disclosure Document before you trade, and FINRA rules require your account to be approved first. Understanding which side of the contract you are on, and what you could owe, comes before any strategy.