Trading term

What is Gamma?

Gamma measures how fast an option's delta changes as the underlying moves — the 'acceleration' of an option's price. High gamma means the delta shifts quickly. Gamma is highest for at-the-money options near expiry, and it drives the fast, whippy moves in short-dated options.

If delta is speed, gamma is acceleration. It tells you how much an option's delta will change for each $1 move in the stock. A high-gamma option's delta ramps up quickly as the stock rises — so the option gains value at an accelerating rate — and falls quickly as it drops. Gamma is largest for at-the-money options and grows dramatically as expiration nears, which is why short-dated at-the-money options move so violently.

Gamma is what makes options non-linear and, for sellers, dangerous. An option seller who is 'short gamma' sees their delta move against them faster and faster as the stock trends — small moves that were harmless become painful. This is 'gamma risk,' and it's why selling short-dated options near the strike can blow up quickly. Buyers of options are 'long gamma': they benefit from big, fast moves because their favourable delta accelerates. Managing gamma is central to any serious options position.

Gamma — the acceleration
highest at the moneyout of the moneyin the moneyGamma peaks at the money and fades in both directions

Gamma is how fast delta itself changes. It peaks at the money — where a small move most changes the option's odds — and fades in both directions. High gamma drives the whippy moves in short-dated options.

For example

An at-the-money option has a delta of 0.50 and a gamma of 0.10. If the stock rises $1, the delta jumps to about 0.60; another $1 and it's ~0.70. The option's sensitivity to the stock keeps increasing — that acceleration is gamma at work.

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Why it matters to you

Gamma is what makes options accelerate — it's why a small move in the stock can cause an outsized swing in an at-the-money option, especially near expiry. Understanding gamma separates traders who get surprised by an option's violent moves from those who anticipate them, and it's the core risk in selling short-dated options.

⚠ Short gamma near expiry is dangerous

Selling at-the-money options close to expiry means being short high gamma — your delta can flip against you fast and hard on even a modest move, turning a small profit into a large loss in minutes. Traders lured by the rich time decay of short-dated options often underestimate the gamma risk lurking underneath it.

Frequently asked questions

What is gamma in options?

Gamma measures how fast an option's delta changes for each $1 move in the underlying — the acceleration of the option's price. High gamma means delta (and thus the option's sensitivity) shifts quickly. It's highest for at-the-money options near expiration.

What's the difference between delta and gamma?

Delta is how much the option moves per $1 in the stock (its speed); gamma is how fast that delta itself changes (its acceleration). Delta tells you current sensitivity; gamma tells you how quickly that sensitivity will shift as the stock moves.

Why is gamma highest at the money?

At the money, a small move in the stock has the biggest effect on whether the option will finish in or out of the money, so its delta changes fastest there. Deep in- or out-of-the-money options have deltas near 1 or 0 that barely move, so their gamma is low.

What is gamma risk?

Gamma risk is the danger faced by option sellers who are 'short gamma': as the stock trends, their delta moves against them faster and faster, so losses accelerate. It's most acute in short-dated at-the-money options, where gamma is extreme, and it's why selling them can blow up quickly.

Related terms

Call optionA call option is a contract giving the buyer the right — but not the obligation — to buy an asset at a fixed 'strike' price before a set expiry date. Call buyers are betting the price will rise; their risk is capped at the premium paid, while the potential profit is open-ended.Cash-secured putA cash-secured put is an options strategy where you sell a put option while setting aside enough cash to buy the stock if you're assigned. You collect the premium as income; in exchange, you agree to buy the stock at the strike if it falls there. It's a way to get paid to buy a stock you want at a lower price.Covered callA covered call is an options strategy where you own 100 shares of a stock and sell a call option against them. You collect the premium as income; in exchange, you cap your upside at the strike. It's a popular way to generate income on shares you're happy to hold or sell.DeltaDelta measures how much an option's price moves for each $1 change in the underlying. A delta of 0.60 means the option gains about $0.60 if the stock rises $1. It ranges from 0 to 1 for calls (0 to −1 for puts) and doubles as a rough probability the option finishes in the money.
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