Options trading: how does it work? The complete guide

In 2025, 15.2 billion options contracts changed hands on US markets, a record for the sixth year in a row, up 26% year on year according to Cboe. On the S&P 500 index, nearly six out of ten options traded expire the same day.

Yet options remain one of the most misunderstood products in finance. They are used to insure a portfolio, to generate income, and to bet on a rise, a fall or even a market that goes nowhere. And they follow a counterintuitive logic: an option can lose value while the stock moves in the right direction. Here is how they work, from the definition to the Greeks, with worked examples.

Options: the 2-minute refresher

An option is a contract. It gives its buyer the right, but not the obligation, to buy or sell an asset (the underlying) at a price set in advance (the strike price), until a given date (the expiry). To obtain this right, the buyer pays the seller a sum of money: the premium.

The simplest way to think about it is insurance. You pay a premium to be covered. If the loss never happens, the premium is gone. If it does, the insurer pays out. The option seller plays the role of the insurer: they collect premiums and pay out when the event occurs.

In this article, premiums are quoted per share. With a contract size of 100, a premium of €4.32 means a contract costing €432.

The call: betting on a rise with a capped loss

Example. A stock trades at €100. You buy a call with a strike price of €105, expiring in 3 months, for a premium of €4.32 per share, or €432 for a contract of 100 shares.

At expiry, there are two possible outcomes:

• The stock finishes below €105: the right to buy at €105 is worthless. You lose the premium, €432, and nothing more.
• The stock finishes above €105: you can buy at €105 a stock that is worth more. Your gain is the difference, minus the premium paid. The break-even point is €109.32 (€105 + €4.32).

Let’s compare with buying 100 shares outright, a €10,000 investment.

Simplified examples, excluding fees. Premium calculated with the Black-Scholes model: 30% volatility, 4% interest rate.

Two lessons. The leverage is considerable in percentage terms, in both directions, but the maximum loss in euros is capped at €432. And it is not enough for the stock to rise: it has to rise far enough, and before expiry.

The put: betting on a fall, or buying insurance

The put is the mirror image of the call: it gains value when the stock falls. It serves two very different purposes.

Speculating on a fall. With the same stock at €100, a 3-month put with a strike price of €95 costs €3.30. If the stock finishes at €85, the put is worth €10: the gain is €6.70 per share, or +203%. If it stays above €95, the premium is lost.

Buying insurance. This is the historical use. You hold 100 shares at €100 and buy a €95 put for €330. Whatever happens before expiry, you will be able to sell your shares at €95. Your maximum loss is known: €500 of decline down to €95, plus €330 of premium, so €830, even if the stock collapses by half. This is the protective put.

Buying or selling an option: two different worlds

Every option has a buyer and a seller. The buyer pays for a right; the seller collects the premium and accepts an obligation. Their risk profiles have nothing in common.

The option seller wins often, but small; they lose rarely, but sometimes big. That is why brokers require margin on short option positions, and often restrict “naked” call selling (without owning the stock) to experienced clients.

How is an option priced?

Intrinsic value and time value

The premium breaks down into two parts:

• Intrinsic value: what immediate exercise would yield. For a call, it is the stock price minus the strike price, if positive. For a put, the opposite.
• Time value: everything else. It is the price of the possibility that the option gains more value before expiry. It melts to zero at expiry.

Our €105 call at €4.32 is out of the money: its premium is made up entirely of time value.

The five pricing parameters

Expected dividends also matter: they push calls down and puts up, since the share price drops by the amount of the dividend on the ex-dividend date.

Black-Scholes and implied volatility

In 1973, Fischer Black and Myron Scholes published a formula linking these parameters to the price of an option, extended the same year by Robert Merton. Scholes and Merton received the Nobel Prize in Economics in 1997, Black having died in 1995. The model’s key idea: an option can be replicated by continuously buying and selling the underlying stock, which pins down a single price, independent of any view on market direction.

Four of the five parameters can be observed directly. The fifth, future volatility, is unknown. So the market runs the calculation backwards: from the option’s price, it derives the volatility that price assumes. This is implied volatility. When a trader says an option is “expensive”, they mean its implied volatility is high relative to the stock’s usual moves.

One last useful relationship: put-call parity. For European options with the same strike price and the same expiry, the call minus the put equals the stock price minus the discounted strike price. In our at-the-money example (strike price €100, 3 months), the call is worth €6.46 and the put €5.46: the gap of roughly €1 corresponds to the cost of financing €100 for three months at 4%. If this equality breaks, arbitrageurs exploit it immediately.

The Greeks: the option’s dashboard

The “Greeks” measure how sensitive an option’s price is to each of its parameters. Back to our call: stock at €100, strike price €105, 3 months to expiry, implied volatility 30%, premium €4.32.

Black-Scholes calculation, 4% rate, no dividend.

Delta is the most widely used Greek. A contract with a delta of 0.43 behaves, for small moves, like 43 shares. It can also be read, roughly, as the probability that the option finishes in the money. And market makers hedge by tracking delta: when they sell calls, they buy the equivalent in shares, then adjust that hedge as delta changes.

Time: the buyer’s enemy

Theta is not constant: it accelerates as expiry approaches. Here is the value of an at-the-money call (stock and strike price at €100, 30% volatility) if the stock does not move.

Black-Scholes calculation, 4% rate, excluding fees.

Time value moves roughly with the square root of the time remaining: dividing the time by four only halves the value. As a result, this call loses more in its final week (€1.70) than during its first month (€1.24).

Volatility: you can be right and still lose

Same call (strike price €105, 3 months, stock at €100), at different levels of implied volatility:

Implied volatility rises ahead of scheduled events (earnings, central bank decisions) and drops right after. This is the volatility crush, or “IV crush”.

Example. The day before earnings: stock at €100, at-the-money call expiring in 7 days, implied volatility 60%. Premium: €3.35. Earnings come out and implied volatility falls back to 30%. Here is the value of the call the next day, depending on how the stock reacts:

Black-Scholes calculation, 4% rate, excluding fees.

The stock rises 2%, and the call loses 16%. Being right on direction is not enough: the move has to exceed what the market had already priced in.

The same bet, three timelines

Back to the €105 call bought at €4.32. The same rise in the stock, at different moments, plus two scenarios where it does not move.

Black-Scholes calculation: constant 30% volatility, 4% rate, excluding fees.

The lesson fits in one sentence. An option is a bet on magnitude and on timing, not just on direction: the stock can take its time, the option cannot.

The most widely used options strategies

The covered call

You hold 100 shares at €100 and sell a 3-month €105 call for €4.32, collecting €432. If the stock stays below €105, you keep the premium: a 4.3% income in three months. If it rises above, your shares are sold at €105 and your gain is capped at €932 (€500 of upside plus €432 of premium). You trade upside potential for income.

The protective put

Buying a put on shares you own to cap the loss, as seen above. It is insurance, and it has a cost: €330 for three months in our example, or 3.3% of the position.

The bull call spread

You buy the €100 call (€6.46) and sell the €105 call (€4.32). Net cost: €2.14. Maximum gain: €2.86 if the stock finishes above €105 (€5 between the strike prices, minus €2.14). Maximum loss: €2.14. You give up the upside beyond €105 to pay three times less for your bet than with a call alone.

The straddle

You buy both the call and the put at €100, for €6.46 + €5.46 = €11.92. You win if the stock moves sharply, in either direction: at expiry, it must finish below €88.08 or above €111.92. It is a bet on volatility, not on direction.

The cash-secured put

You sell a €95 put for €3.30, keeping enough cash aside to buy the shares. If the stock finishes above €95, you keep the premium. Otherwise, you buy 100 shares at €95, for a cost basis of €91.70 once the premium is deducted. It is a way to get paid while waiting for an entry point.

Which strategy for which situation?

Buying an option means paying for the right to be wrong without losing everything. Selling one means getting paid to carry other people’s risk. The right side depends on what you want to be: the insured or the insurer.

0DTE options: the trend that divides opinion

“0DTE” options (zero days to expiration) expire the same day. In 2025, they accounted for 59% of S&P 500 index options volume, or 2.3 million contracts a day, according to Cboe. Retail investors make up nearly half of total US options volume.

Their appeal is obvious: very low premiums and spectacular moves. Their mechanics are less so. A few hours from expiry, gamma is extreme: delta can swing from almost 0 to almost 1 on a modest move in the index. And theta is at its peak: our table shows that an at-the-money call loses €0.32 on its final day, half its value. A 0DTE option is closer to very short-term trading than to investing.

Advantages of options

• Loss limited to the premium for the buyer, known at purchase.
• Leverage: a small stake gives significant exposure.
• Flexibility: profit from a rise, a fall, a flat market or volatility itself.
• Insurance: a put protects a portfolio without selling the holdings.
• Income: selling options lets you collect premiums on existing positions.

Disadvantages of options

• Complexity: the price depends on five parameters, including implied volatility, which many investors never see.
• Time works against the buyer: an option loses value every day, faster and faster.
• High probability of loss for the buyer: an out-of-the-money option often expires worthless.
• High risk for the seller: potentially unlimited loss on a naked short call.
• Uneven liquidity: on thinly traded options, the gap between the bid and ask prices can be costly.
• Regulated access: in Europe, options are complex instruments under MiFID II, and the broker must check that you understand how they work before giving you access.

Options, stocks or leverage: the comparison

Real-world case: April 2025, when volatility exploded

On 2 April 2025, after the close, the US administration announces a wave of tariffs. On 4 April, during a session in which the S&P 500 falls 6%, the US options market breaks its all-time record with 101 million contracts traded, and S&P 500 options set their own record at 6.04 million contracts, according to Cboe. On 7 April, the VIX, which measures the implied volatility of S&P 500 options, hits 60.13 intraday, its fifth-highest level since 1990, according to Barchart. After a pause on those tariffs is announced on 9 April, it drops by nearly 36%, according to Saxo.

Two lessons for every investor:

1. Insurance is bought before the fire. Puts bought in late March, when the VIX was still around 22, gained enormously in value. Those bought at the height of the panic were priced with extreme implied volatility, and lost much of their value as soon as volatility fell back.
2. Volume is not a buy signal. The record number of contracts traded coincided with the moment when options were among the most expensive since the Covid crisis of 2020.

Options are complex instruments that carry a high risk of capital loss, which can exceed the stake for the seller. This article is educational and does not constitute investment advice.