Strike Price: Definition, How It Works, and How to Choose One
How the Strike Price Works
The strike price is the most important number in any options contract. It’s the line in the sand — the price that determines whether your option has value at expiration or expires worthless.
When you buy a call option, the strike price is the price you’d pay to buy 100 shares if you exercise. When you buy a put option, it’s the price you’d receive for selling 100 shares. The question is always the same: is the current stock price favorable compared to the strike?
Here’s a concrete example. A stock trades at $100. You buy a call with a $105 strike. That means you have the right to buy at $105 no matter where the stock goes. If the stock rises to $120, you can buy at $105 — a $15 advantage. If the stock stays at $100 or drops, your right to buy at $105 is worthless because you could buy cheaper on the open market.
Strike Price and Moneyness
The relationship between the strike price and the current stock price defines the option’s “moneyness” — whether it currently has intrinsic value.
| Moneyness | Call Option | Put Option | Intrinsic Value? |
|---|---|---|---|
| In the Money (ITM) | Stock price > Strike price | Stock price < Strike price | Yes |
| At the Money (ATM) | Stock price ≈ Strike price | Stock price ≈ Strike price | Approximately zero |
| Out of the Money (OTM) | Stock price < Strike price | Stock price > Strike price | No |
This is the core framework. An in-the-money option has intrinsic value because exercising it would be immediately profitable (ignoring the premium paid). An out-of-the-money option has zero intrinsic value — its entire premium is time value, which decays as expiration approaches.
How Strike Price Affects the Premium
The strike price directly determines how much you pay for an option. The relationship is intuitive once you understand moneyness:
For Call Options
| Strike Price | Relative to Stock | Premium | Why |
|---|---|---|---|
| Lower strike | Deep ITM | Expensive | Already has significant intrinsic value |
| Near stock price | ATM | Moderate | No intrinsic value, but highest time value |
| Higher strike | OTM | Cheap | No intrinsic value, needs stock to move up significantly |
For Put Options
| Strike Price | Relative to Stock | Premium | Why |
|---|---|---|---|
| Higher strike | Deep ITM | Expensive | Already has significant intrinsic value |
| Near stock price | ATM | Moderate | No intrinsic value, but highest time value |
| Lower strike | OTM | Cheap | No intrinsic value, needs stock to drop significantly |
This creates a direct tradeoff: cheaper options (further OTM) have a lower probability of profit but offer higher percentage returns if the stock makes a big move. More expensive options (ITM) cost more upfront but have a higher probability of retaining some value.
Real-World Example: Choosing a Strike
Microsoft (MSFT) trades at $420. You’re bullish and want to buy a call option expiring in 60 days. Here’s how different strikes compare:
| Strike Price | Moneyness | Premium (approx.) | Breakeven | Probability of Profit |
|---|---|---|---|---|
| $400 | Deep ITM | $25.00 ($2,500) | $425.00 | Higher (~60%) |
| $420 | ATM | $12.00 ($1,200) | $432.00 | Moderate (~45%) |
| $440 | OTM | $4.50 ($450) | $444.50 | Lower (~25%) |
| $460 | Deep OTM | $1.50 ($150) | $461.50 | Low (~12%) |
If MSFT climbs to $450 at expiration:
| Strike | Cost | Intrinsic Value at $450 | Profit | Return on Investment |
|---|---|---|---|---|
| $400 | $2,500 | $5,000 | $2,500 | 100% |
| $420 | $1,200 | $3,000 | $1,800 | 150% |
| $440 | $450 | $1,000 | $550 | 122% |
| $460 | $150 | $0 | −$150 | −100% |
Notice the tradeoff: the $420 ATM call delivers the best percentage return in this scenario, but the $400 ITM call delivers the highest dollar profit and would still be profitable even if MSFT only reached $426. The $460 call costs the least but needs a massive move to work — and in this case, it expires worthless.
How to Choose a Strike Price
There’s no universally “correct” strike. Your choice depends on your conviction, risk tolerance, and strategy.
| If You Want… | Choose This Strike | Tradeoff |
|---|---|---|
| Higher probability of profit | ITM strike | More expensive, lower percentage returns |
| Balance of cost and probability | ATM strike | Moderate cost, stock needs to move beyond breakeven |
| Cheap entry, big potential % return | OTM strike | Low probability of profit, high risk of total loss |
| Stock replacement (similar to owning shares) | Deep ITM strike | Expensive, high delta (~0.80+), moves nearly 1:1 with stock |
| Lottery ticket on a big move | Deep OTM strike | Very cheap, very low probability, often expires worthless |
Strike Price and the Greeks
The strike price you choose directly affects your exposure to the Options Greeks:
| Greek | ITM Strike | ATM Strike | OTM Strike |
|---|---|---|---|
| Delta | High (0.60–0.95) | ~0.50 | Low (0.05–0.40) |
| Gamma | Lower | Highest | Lower |
| Theta (time decay) | Lower | Highest | Lower in absolute $, but highest as % of premium |
| Vega | Lower | Highest | Lower |
ATM options are the most sensitive to time decay, volatility changes, and gamma — they’re the most “reactive” to market conditions. Deep ITM options behave more like the stock itself. Deep OTM options are cheap but fragile — a small adverse move in the underlying or a drop in implied volatility can wipe out most of their value quickly.
Strike Prices and Option Chains
When you look at an option chain on your broker’s platform, you’ll see a list of available strikes for each expiration date. Strikes are set by the options exchange at fixed intervals — typically $1, $2.50, $5, or $10 apart, depending on the stock’s price and trading volume.
Higher-priced stocks tend to have wider strike intervals. Heavily traded names like Apple, Tesla, and SPY have strikes at every $1 or even $0.50 increment near the current price, giving you finer control over your positioning.
Strike Price in Common Strategies
| Strategy | Strike Selection | Why |
|---|---|---|
| Covered Call | OTM strike above current price | Generates premium income while allowing some upside on shares |
| Protective Put | OTM strike below current price | Provides downside floor at a lower cost than ATM puts |
| Bull Call Spread | Buy lower strike call + sell higher strike call | Lower net cost, capped profit between the two strikes |
| Iron Condor | Sell OTM call + OTM put, buy further OTM call + put | Profit zone defined by the inner strikes; wings limit risk |
| Straddle | Buy call + put at the same ATM strike | Maximizes sensitivity to a big move in either direction |
Key Takeaways
- The strike price is the fixed price at which an option holder can buy (call) or sell (put) the underlying asset.
- Strike price determines moneyness: whether the option is in the money, at the money, or out of the money.
- Lower strikes make calls more expensive and puts cheaper; higher strikes do the opposite.
- ITM strikes cost more but have higher probability of profit. OTM strikes are cheap but usually expire worthless.
- ATM options have the highest gamma, theta, and vega — they’re the most reactive to market changes.
- Delta roughly approximates the probability of finishing in the money, making it a useful tool for strike selection.
Frequently Asked Questions
What is a strike price in simple terms?
The strike price is the price at which you can buy or sell a stock if you exercise your option. If you hold a call with a $50 strike, you can buy the stock at $50 regardless of its current market price. If you hold a put with a $50 strike, you can sell at $50.
Does the strike price change?
No. The strike price is fixed when the option contract is created and stays the same until expiration. The underlying stock price moves, the premium fluctuates, but the strike never changes. The only exception is corporate actions like stock splits, where strikes are adjusted proportionally.
What is the best strike price to choose?
It depends on your strategy and conviction. ATM strikes offer a balance of cost and probability. ITM strikes are more conservative (higher cost, higher probability). OTM strikes are more aggressive (lower cost, lower probability). There’s no single “best” — it’s a tradeoff between risk, reward, and likelihood.
What does it mean when an option is “at the money”?
An at-the-money option has a strike price equal to (or very close to) the current stock price. ATM options have no intrinsic value but carry the highest time value. They’re the most common choice for traders who want balanced exposure to both direction and volatility.
How does the strike price affect breakeven?
For a call option, your breakeven is the strike price plus the premium paid. For a put option, it’s the strike price minus the premium paid. The further OTM your strike, the further the stock needs to move for you to break even.
Why are there so many strike prices available?
Options exchanges list multiple strikes to give traders flexibility. Heavily traded stocks have strikes at narrow intervals ($1 or $2.50), while less liquid names have wider intervals ($5 or $10). New strikes can be added as the stock price moves or as demand increases.
Related Terms
| Term | Definition |
|---|---|
| Option | A contract giving the right to buy or sell an asset at a set price before expiration |
| Premium | The price paid to buy an options contract |
| Expiration Date | The last date on which the option can be exercised |
| In the Money | When an option has intrinsic value based on the strike vs. stock price |
| Out of the Money | When an option has no intrinsic value — strike is unfavorable vs. stock price |
| Intrinsic Value (Options) | The amount by which an option is in the money |
| Delta | Measures sensitivity of an option’s price to a $1 move in the underlying |