What is Gamma? The Options Greek Explained
Master gamma, the Greek that controls how fast your options exposure changes. Learn why gamma is critical for risk management and how it shapes market dynamics.
Gamma
measures how much an option's delta changes for a $1 move in the underlying stock. It represents the acceleration of an option's price, telling you how quickly your directional exposure is shifting.
Gamma is highest for at-the-money options near expiration and lowest for deep ITM/OTM options. High gamma means your position can change dramatically with small stock moves.
Gamma = how fast delta changes per $1 stock move. Think of it as acceleration vs speed (delta = speed). ATM options have highest gamma. Near-expiration options have highest gamma. Gamma is your friend when buying options (gains accelerate) and your enemy when selling (losses accelerate). Gamma risk is why most professionals close short options before expiration week.
Gamma measures how fast delta changes as the underlying moves — highest for at-the-money options near expiration, where small moves swing delta sharply.
What is Gamma?
If delta is the speed of your options position, gamma is the acceleration. Gamma measures how much delta changes for every $1 the stock moves. It's the Greek that determines whether your gains (or losses) accelerate or decelerate.
Example: Your AAPL call has a delta of 0.50 and gamma of 0.04. AAPL rises $1. Your delta increases from 0.50 to 0.54 (0.50 + 0.04). The next $1 rise, delta moves from 0.54 to 0.58. Each dollar of stock movement creates progressively larger option gains—that's gamma working for you as a buyer.
Key Gamma Characteristics
ATM Options Have the Highest Gamma
Gamma peaks at-the-money because that's where the probability of expiring ITM is most uncertain—small stock moves create the biggest changes in probability (delta). Deep ITM and deep OTM options have low gamma because their outcome is more certain.
Gamma Increases Near Expiration
With 60 days to expiration, gamma might be 0.02. With 1 day to expiration, gamma can spike to 0.15+. This is why the last few days before expiration are called "gamma week"—positions become incredibly sensitive to stock movement.
Long Gamma vs Short Gamma
Long gamma (option buyers): Gamma works in your favor. As the stock moves in your direction, delta increases and your gains accelerate. As it moves against you, delta decreases and your losses decelerate. Long gamma is like having a built-in cushion.
Short gamma (option sellers): Gamma works against you. Losses accelerate and gains decelerate. A covered call writer or iron condor seller near expiration faces significant gamma risk if the stock moves to their short strike. This is the primary risk of selling options near expiration.
Key Takeaways
- Gamma = how fast delta changes per $1 stock move (acceleration vs speed)
- Highest for ATM options near expiration, lowest for deep ITM/OTM
- Long gamma (buyers) = gains accelerate, losses decelerate
- Short gamma (sellers) = losses accelerate, gains decelerate
- Close short options before expiration week to avoid gamma risk
Gamma never acts alone. It accelerates delta — and at index scale, dealer gamma hedging moves the whole market (see gamma exposure). For how all five Greeks fit together, start with the options Greeks guide.
Frequently Asked Questions
Is high gamma good or bad?
It depends on your position. For option buyers, high gamma is good—it means your profits accelerate as the stock moves in your favor (delta increases). For option sellers, high gamma is dangerous—it means losses accelerate as the stock moves against you. This is why short gamma positions near expiration are the riskiest trades in options.
When is gamma highest?
Gamma is highest for at-the-money (ATM) options close to expiration. A 0DTE ATM option might have gamma of 0.15 or higher, meaning delta changes by 0.15 for every $1 stock move. For comparison, a 90-day ATM option might have gamma of only 0.02. This is why expiration week is called 'gamma week.'
What is gamma risk?
Gamma risk is the danger that your position's delta (and therefore P&L) changes rapidly with small stock moves. Short gamma positions (sold options) face the worst gamma risk: a $2 move in the stock can turn a small loss into a large one as delta accelerates against you. This is why professionals close short options 7-10 days before expiration.
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