How gamma works

Gamma measures the rate at which an option's delta changes for every one-point move in the underlying asset's price, serving as a key indicator of an option's price sensitivity.

Gamma is a second-order Greek, meaning it measures the sensitivity of another Greek, specifically delta. While delta tells you how much an option's price is expected to change for a one-dollar move in the underlying asset, gamma tells you how much that delta itself will change. Imagine delta as the speed of a car; gamma is like the acceleration or deceleration of that car. A high gamma implies that the option's delta will fluctuate significantly with minor price movements in the underlying asset. Conversely, a low gamma suggests that delta will be relatively stable, even with larger swings in the underlying price. This characteristic makes gamma particularly important for options traders, as it provides insight into the stability of their delta hedging positions. It is highest for at-the-money options and decreases as an option moves further in- or out-of-the-money, reflecting the decreasing sensitivity of delta to further price changes. As an option approaches expiration, its gamma typically increases dramatically, especially for at-the-money options. This phenomenon is often referred to as 'gamma squeeze' potential, where small price movements can lead to very large changes in delta and, consequently, in the option's value. Traders who are long gamma benefit from increased price volatility, as their delta position becomes more favorable with underlying price swings, while those who are short gamma face increased risk during volatile periods. Understanding gamma is crucial for effective risk management and for anticipating how an option's price will behave as the underlying asset moves.

Why it matters

Common mistakes

- One common mistake is ignoring gamma when delta hedging. Without considering gamma, a delta-neutral position can quickly become unhedged with even small movements in the underlying asset, leading to unexpected losses.
Another error is underestimating the impact of increasing gamma as expiration approaches. At-the-money options can experience dramatic and sudden shifts in their delta, making risk management much more challenging.
Traders sometimes fail to understand that a positive gamma benefits from volatility while a negative gamma is hurt by it. Misinterpreting this relationship can lead to strategies that are inadvertently exposed to significant downside risk during turbulent market conditions.
Overlooking the relationship between gamma and an options strike price and time to expiration is another common pitfall. Gamma is highest for at-the-money options with less time until expiration, a factor that profoundly impacts trading decisions.

FAQs

What is the main difference between delta and gamma?

Delta measures the rate of change of an option's price relative to the underlying asset's price. Gamma, on the other hand, measures how much that delta itself will change for a one-point move in the underlying, essentially the rate of change of delta.

Why is gamma highest for at-the-money options?

At-the-money options have the highest uncertainty about whether they will expire in or out of the money. Therefore, their delta is most sensitive to changes in the underlying price, resulting in a higher gamma.

Does gamma increase or decrease closer to expiration?

Gamma generally increases significantly as an option approaches its expiration date, especially for at-the-money options. This rapid rise in gamma can lead to very large and sudden swings in the option's delta and price.