What Is GEX? Gamma Exposure, Explained

By The Oracle · For education, not financial advice.

Gamma exposure (GEX) is an estimate of how much stock options dealers would have to buy or sell to stay hedged as the price moves. Where GEX is positive, their hedging tends to lean against moves and calm price down. Where it is negative, their hedging tends to go with moves and speed price up. To read GEX levels, find three prices: the gamma flip, where total GEX changes sign; the call wall, the largest positive strike above the price; and the put wall, the largest negative strike below it.

Using MomoEdge? The GEX tab lesson shows where each level sits on screen. This guide covers the idea behind it.

Why dealers hedge at all

When you buy or sell an option, the other side is often a market maker, which we will call a dealer. Dealers aim to earn the spread, not to bet on direction, so they offset the directional risk of the options they hold by trading the stock or its futures. That offset is the delta hedge.

Delta is how much an option’s price moves for a $1 move in the stock. Gamma is how fast delta itself changes. When a dealer’s book carries a lot of gamma, every move in the stock changes the hedge they need, so they have to keep trading. GEX adds that up across the option chain to estimate how large that trading is, and which way it leans.

How GEX is calculated

For each strike, the usual formula is gamma × open interest × 100 × price² × 0.01. The 100 is the contract multiplier. Multiplying by the price turns shares into dollars, and the extra price × 0.01 scales the answer to a 1% move. Some tools quote GEX per $1 move or as a share count instead, so numbers from two providers are rarely comparable.

Then comes the sign, and this is where the assumptions live.

Some providers try to shrink that error by estimating positions from where trades filled, rather than from open interest alone. That helps, but the result is still an estimate. Treat every GEX number as a model of positioning, not a measurement of it.

Positive and negative gamma

• Positive gamma. A dealer who is long gamma finds their position getting longer as price rises and shorter as it falls. To stay flat, they sell into rallies and buy into dips. That leans against the move, so ranges tend to be tighter and price tends to drift back toward heavy strikes.
• Negative gamma. A dealer who is short gamma has to buy as price rises and sell as it falls. That adds to the move, so swings tend to be larger and breaks tend to run further.

“Tend to” matters. Hedging is one force among many, and news, earnings or a large order from someone else can overwhelm it on any given day. Positive vs negative gamma goes further into both.

How to read GEX levels

Most GEX charts show one bar per strike, with positive GEX on one side and negative on the other. Read them in this order.

• The gamma flip. The estimated price where total GEX changes from positive to negative. It is found by recomputing total gamma at a range of prices, not by reading a single bar. Above it, the model expects calmer trading; below it, faster. Close to it, the regime itself is unstable, and a small move can change it.
• The call wall. The strike with the largest positive GEX above the price. Dealer selling into strength is estimated to be heaviest there, so it is often read as a ceiling.
• The put wall. The strike with the largest negative GEX below the price. It is often read as a floor, but the hedging math is mixed: at a negative strike, hedging tends to extend a move, so a level that holds for a while can become an accelerant once it breaks.
• Total GEX. The sum across all strikes. A large positive total suggests a market that absorbs moves; a negative total suggests one that amplifies them.

None of these are lines price must respect. They mark where hedging pressure is estimated to be heaviest. Each has its own guide: the gamma flip, and call and put walls.

A worked example

Take the 105 strike. Say it has 20,000 calls of open interest, each with a gamma of 0.04. A 1% move here is $1, so each contract’s delta changes by 0.04, which is 4 shares per contract. Across 20,000 contracts that is 80,000 shares, or about $8 million of stock. Because the convention treats calls as dealer-long, it counts as +$8M.

Now read the whole picture. XYZ sits above the flip, so the model expects dealer hedging to lean against moves. A rally toward 105 meets the heaviest estimated dealer selling. A drop through 97.50 puts the stock in negative gamma, and a break of 95 is where hedging is estimated to add the most to the move.

Then test the assumption. If the calls at 105 had been bought by customers rather than sold by them, dealers would be short those calls, the +$8M would really be −$8M, and the read above $100 would change completely. That is why the sign convention deserves as much attention as the bars.

Where GEX works best, and where it fails

• Index products work best. SPX, SPY and QQQ have deep options markets where dealers carry much of the open interest, so the hedging story is strongest there. In a single stock, a few large traders can dominate the chain, and they may not hedge the way dealers do.
• Open interest is a day old. It is counted once a day, overnight. Positions opened and closed within the session, which includes most same-day (0DTE) trading, never show up in it.
• Other forces move the hedge. Changes in implied volatility (vanna) and the passage of time (charm) change deltas even when price stands still, so hedging can happen with no move at all.
• Walls move. As traders roll and close positions, the largest strikes shift, sometimes within a day.
• Events override it. Around a Fed decision, an inflation report or earnings, new information can swamp any hedging effect.

A short routine

Before the open, note whether the ticker sits above or below its flip, then mark the call wall and the put wall. During the session, watch how price behaves as it nears them: does it stall, or slice through? Weigh that against the chart, the volume and the news. GEX tells you where hedging may matter. It does not tell you which way the stock will go.

Seeing it in MomoEdge

MomoEdge’s GEX tab draws these estimates strike by strike for one ticker at a time, with the wall, the support and the flip marked, and PRISM maps gamma across strikes and expirations. The GEX tab lesson shows each level on screen, and the Terminal Field Guide explains when to turn to GEX and PRISM from a trade on screen. GEX is positioning; for how it differs from the trades printing today, see options flow vs GEX. The $10K account lists every trade our team takes with real money, winners and losers, before commissions and fees. If you would like to follow these levels on live data, you can see what the terminal includes.

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