Stock Options Explained: How to Trade Calls and Puts

What Is a Stock Option?

A stock option is a financial contract that gives you the right—but not the obligation—to buy or sell 100 shares of an underlying stock at a predetermined price (called the strike price) before or on a specific date (called the expiration date).

Options are classified as derivatives because their value is derived from the price of the underlying stock. Unlike buying shares directly, options give you leverage: you can control 100 shares for a fraction of the cost of buying them outright.

Calls vs Puts: Understanding the Difference

What Is a Call Option?

A call option gives you the right to buy 100 shares of a stock at the strike price before expiration. You buy calls when you're bullish—expecting the stock price to rise.

Example: You buy a call option on Apple (AAPL) with a $150 strike price expiring in 30 days for $5 per share ($500 total). If Apple rises to $170, your option is worth at least $20 per share ($2,000 total), giving you a $1,500 profit. If Apple stays below $150, your option expires worthless and you lose the $500 premium.

What Is a Put Option?

A put option gives you the right to sell 100 shares of a stock at the strike price before expiration. You buy puts when you're bearish—expecting the stock price to fall.

Example: You buy a put option on Tesla (TSLA) with a $200 strike price for $8 per share ($800 total). If Tesla drops to $150, your put is worth at least $50 per share ($5,000 total), giving you a $4,200 profit. If Tesla stays above $200, your put expires worthless.

Put vs Call Option: Quick Comparison

Anatomy of an Option Contract

Every option contract has five key components:

Reading an Option Symbol

Option symbols follow a standardized format. For example: AAPL250221C00150000

• AAPL - Underlying stock (Apple)
• 250221 - Expiration date (February 21, 2025)
• C - Option type (C = Call, P = Put)
• 00150000 - Strike price ($150.00)

How Do Stock Options Work?

Intrinsic Value vs Time Value

An option's price (premium) consists of two parts:

• Intrinsic Value: The amount the option is "in the money." For a call, it's the stock price minus the strike price (if positive). For a put, it's the strike price minus the stock price.
• Time Value (Extrinsic Value): The extra premium based on time remaining until expiration and expected volatility. This portion decays as expiration approaches.

In the Money, At the Money, Out of the Money

How Do Call Options Work? A Step-by-Step Example

How to Buy Options

Getting started with options trading requires a few steps beyond regular stock trading:

Step 1: Open a Brokerage Account

Choose a broker that offers options trading. Popular choices include Fidelity, Charles Schwab, TD Ameritrade, Interactive Brokers, and Robinhood. Look for competitive options commissions and a good trading platform.

Step 2: Get Approved for Options Trading

Brokers require you to apply for options trading approval. You'll answer questions about your:

• Investment experience and knowledge
• Financial situation (income, net worth)
• Trading objectives
• Risk tolerance

Approval levels range from Level 1 (covered calls, cash-secured puts) to Level 4 (naked options). Beginners typically start at Level 1 or 2.

Step 3: Fund Your Account

Options can be purchased for less capital than stocks, but you still need sufficient funds. Some strategies (like selling puts) require holding cash or margin as collateral.

Step 4: Research Your Trade

Before placing an order, consider:

• Direction: Do you expect the stock to rise (call) or fall (put)?
• Timeframe: How long do you expect the move to take?
• Strike selection: ITM options cost more but have higher probability. OTM options are cheaper but riskier.
• Implied volatility: High IV means expensive options. Low IV means cheaper options.

Step 5: Place Your Order

Use your broker's options chain to select your contract. Choose between:

• Market order: Execute immediately at current price
• Limit order: Set your maximum price (recommended for options)

Options vs Stocks

Understanding the differences between options and stocks helps you choose the right instrument for your strategy:

When to Use Options Instead of Stocks

• Limited capital: Control 100 shares for a fraction of the cost
• Hedging: Protect existing stock positions with puts
• Generating income: Sell covered calls on stocks you own
• Defined risk: Know your maximum loss upfront
• Bearish plays: Profit from declining prices without short selling

Options Greeks Explained

The "Greeks" are metrics that measure different risk factors affecting an option's price. Understanding them is essential for managing options positions.

Delta (Δ)

What it measures: How much the option price changes for every $1 move in the underlying stock.

• Call options: Delta ranges from 0 to 1.00 (or 0 to 100)
• Put options: Delta ranges from -1.00 to 0 (or -100 to 0)
• ATM options: Have delta around 0.50 (50)
• Use case: A 0.60 delta call gains $0.60 when the stock rises $1

Gamma (Γ)

What it measures: The rate of change of Delta. How much Delta changes when the stock moves $1.

• Highest for ATM options near expiration
• Important for understanding how Delta accelerates
• High gamma = more sensitivity to stock price changes

Theta (Θ)

What it measures: Time decay - how much value the option loses each day.

• Always negative for buyers (you lose value daily)
• Always positive for sellers (you gain from decay)
• Accelerates as expiration approaches
• Example: Theta of -0.05 means the option loses $5 per day (per contract)

Vega (V)

What it measures: Sensitivity to changes in implied volatility (IV).

• Shows how much the option price changes for each 1% change in IV
• Higher for longer-dated options
• High IV: Options are expensive (good for sellers)
• Low IV: Options are cheap (good for buyers)

Rho (Ρ)

What it measures: Sensitivity to interest rate changes.

• Usually the least important Greek for short-term traders
• More relevant for long-dated options (LEAPS)
• Calls increase in value when rates rise
• Puts decrease in value when rates rise

Risks of Trading Options

Options trading carries significant risks that every trader should understand:

1. Total Loss of Premium

When you buy options, you can lose 100% of your investment if the option expires worthless. Unlike stocks, which can recover over time, options have an expiration date.

2. Time Decay (Theta)

Every day that passes, your option loses value due to time decay. This works against option buyers and requires the stock to move enough to overcome this decay.

3. Leverage Amplifies Losses

While leverage can multiply gains, it equally multiplies losses. Small adverse moves in the stock can result in large percentage losses in your option position.

4. Complexity

Options involve multiple variables (strike, expiration, IV, Greeks) that affect pricing. Misunderstanding these can lead to poor trading decisions.

5. Unlimited Risk (Selling Naked Options)

While buying options limits your loss to the premium, selling naked calls has theoretically unlimited risk, and selling naked puts can result in massive losses if the stock crashes.

Frequently Asked Questions