What Is Dealer Gamma Exposure (GEX)? How Options Hedging Moves the Market

Dealer gamma exposure, often shortened to GEX, measures how options dealers are forced to trade the underlying market as it moves in order to stay hedged. When dealers are net long gamma they trade against the move and dampen volatility, and when they are net short gamma they trade with the move and amplify it. It describes the mechanical push on prices from hedging, not a market view.

Options dealers are usually on the other side of the trades investors put on, and they hedge that risk continuously. The aggregate of that hedging can quietly pin an index in place or make its swings larger. This page explains what gamma is, why dealer hedging moves markets, what long versus short gamma does, and how Kresmion reads it. It is descriptive throughout.

What gamma is

If calls and puts are new to you, start with what a call option and a put option are. An option's delta is how much its price moves when the underlying moves. Gamma is how fast that delta itself changes. Because delta shifts as the market moves, a dealer who has sold or bought options has to keep rebuying or reselling the underlying to stay hedged, and gamma governs how much rehedging each move forces.

Dealer gamma exposure adds up that effect across all the options open on an index and expresses it as the amount of the underlying dealers must trade per one percent move. The sign is what matters most.

Long gamma dampens, short gamma amplifies

When dealers are net long gamma, staying hedged means selling into strength and buying into weakness. That is stabilizing: it leans against the move and tends to compress realized volatility, which is why a strongly positive reading often coincides with a market that feels pinned and quiet.

When dealers are net short gamma, the hedging flips. Staying hedged means buying into strength and selling into weakness, which pushes the move further. A negative reading tends to coincide with larger, faster swings, because the hedging is pro cyclical.

The zero gamma level

Between positive and negative there is a crossover price, the zero gamma level or flip point. Above it dealers are net long gamma and dampening; below it they are net short gamma and amplifying. When an index trades right at its flip level, small moves in either direction can be self reinforcing, because the hedging behavior changes character as price crosses the line. Kresmion has published notes where one index sat pinned on its flip level for days while another stayed in amplifying territory, a setup where the same catalyst can move two indices by very different amounts.

What GEX does not tell you

Dealer gamma is about volatility, not direction. A positive reading does not say the market will go up, only that dealer hedging is likely to dampen how far it moves. A negative reading does not say the market will fall, only that a move, either way, is likely to be exaggerated. It is also a snapshot of current positioning that can change as options are opened, closed, and expire, so it is read as a conditional map of how a move might travel, not a forecast of whether one happens.

How Kresmion tracks it

Kresmion computes dealer gamma per index (for example the S&P 500, the Nasdaq 100, and the Russell 2000) and reports the sign, the level, and where spot sits relative to the flip point, alongside its other positioning layers. The value is in comparing indices: when large caps are long gamma and small caps are short gamma into an event, the market can look calm on the surface while the more fragile part sits underneath.

Key takeaways

Frequently asked questions

What is the difference between delta and gamma?

Delta is how much an option's price moves for a move in the underlying. Gamma is how fast that delta changes as the underlying moves. Gamma is why a hedged dealer has to keep adjusting the hedge rather than setting it once.

Does positive gamma mean the market will go up?

No. Positive dealer gamma means dealer hedging tends to dampen volatility, selling into strength and buying into weakness. It is about how far the market moves, not which way.

What is the zero gamma or flip level?

It is the price at which aggregate dealer gamma crosses from positive to negative. Above it hedging dampens moves; below it hedging amplifies them. An index sitting right on its flip level is in a sensitive spot, because the hedging behavior changes as price crosses.

Why does 0DTE options activity matter for gamma?

Options that expire the same day carry very large gamma near their strike, so a heavy volume of them can concentrate dealer hedging around current prices. That can intensify both the pinning effect when dealers are long gamma and the amplifying effect when they are short, which is why short dated options get attention in gamma analysis.

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Source: dealer gamma is derived from listed options open interest and standard options pricing (the second derivative of option value with respect to the underlying). Kresmion computes gamma exposure per index from options snapshots. This page is information, not investment advice. Kresmion Research.