What Is a Gamma Squeeze? How Options Hedging Can Accelerate a Move

A gamma squeeze is a price rise that options hedging pushes further, as dealers who sold call options buy more stock to stay hedged while the price climbs.

The buying comes from risk management, not from a view on the company, and it can add to a move that other buyers started. The term is used loosely, often for any sharp rise in a stock with busy options trading. This page covers the hedging mechanics behind it, why heavy buying of short-dated calls is the usual setup, how it differs from a short squeeze, how the hedging pressure fades, what the SEC staff found when it looked for one in GameStop in January 2021, and what modeled gamma data can and cannot show about it. It is descriptive throughout.

The hedging mechanics

If calls and puts are new to you, start with what a call option and a put option are. A market maker that sells a call to a customer takes on the opposite of the customer's position: it loses if the stock rises. A market maker that wants to stay neutral to small moves hedges by buying shares, roughly the call's delta times 100 per contract.

That first purchase is only the start. Delta is not fixed. Gamma is the rate at which delta changes as the stock moves, so when the stock rises, each short call's delta grows and the hedge is too small. Staying hedged means buying more shares into the rise. When the stock falls, delta shrinks and the hedge is too large, so the market maker sells shares into the fall. That pattern, buying into strength and selling into weakness, is what being net short gamma means, and it is the amplifying case described in dealer gamma exposure. A dealer that is net long gamma does the reverse and leans against moves.

A gamma squeeze is the rising leg of that loop running on a large scale. The stock climbs, the calls sold to customers gain delta, hedgers buy shares, and that buying is one more source of demand while the price is already rising. The loop only runs while hedgers are net short gamma at strikes near the current price. Customer buying of puts also leaves dealers short gamma, but the first hedge on a sold put is a sale of stock, so the term is attached to call buying, where the first hedge and the follow-on rehedging are both purchases as the price rises.

Why concentrated short-dated call buying is the usual setup

Two things set the size of the hedging. The first is how much gamma sits near the current price, which depends on how many contracts are open at nearby strikes, a count published as open interest. The second is time to expiry, because an at the money option's gamma grows as its expiry approaches while an out of the money option's gamma collapses in the final days.

The table below uses the Black-Scholes model with illustrative inputs, not market data: a stock at 100, implied volatility of 25%, a 4% rate, no dividend, with days counted as calendar days over a 365-day year. The dollar figure is the hedge change for one contract per 1% move in the stock, computed as gamma times 100 times spot squared times 0.01.

The pattern is the setup. A short-dated contract near the stock's price forces far more rehedging per move than a long-dated one, and a short-dated contract a few strikes away forces almost none. When buyers crowd into short-dated calls at strikes just above the price, the hedging need is small while the stock sits below those strikes and grows sharply as the price reaches them. Each strike the price crosses brings a new layer of contracts into the zone where their gamma peaks.

Options with zero days to expiration (0DTE) are the extreme case: on their last trading day, gamma near the strike is at its largest and falls away within a short distance of it. Some products now list expirations daily: Cboe offers standard, weekly and daily expirations on S&P 500 index (SPX) options. Short-dated gamma is local, though. It matters only where the price actually trades, and much of it disappears at the end of the session.

Gamma squeeze versus short squeeze

A short squeeze is buying by short sellers closing positions that are losing money, often under margin pressure. A gamma squeeze is buying by options hedgers adjusting a hedge. Both are purchases that respond to a rising price rather than to new information, and both can run at the same time in the same stock, which is why the two are often confused.

The difference is who is buying and why. A short seller who covers is done: the position is closed and the buying stops. A hedger keeps adjusting as long as the options stay open and the price keeps moving, in both directions. Measures of short activity describe the first mechanism, not the second. Short volume, for example, is a daily flow count in which much of the activity is market makers filling orders, so it says little about either squeeze on its own.

How the hedging pressure fades

The same arithmetic that builds the pressure also removes it, and time does much of the work. As expiry nears, an out of the money call's delta decays toward zero even if the stock stands still, so the shares held against it are no longer needed and are sold. That time effect is charm, or delta decay. A call that finishes in the money reaches a delta of one, and for an option on a stock the shares held against it are delivered to the call holder on assignment. Either way, the hedge that fed the move is released once the contracts expire.

The loop can also stop earlier. Buyers can sell their calls back, which lets dealers unwind the hedge. A falling price reverses the loop, because short gamma means selling into weakness. And a change in implied volatility changes deltas on its own, which is the subject of vanna exposure.

The GameStop case: what the SEC staff found

GameStop in January 2021 is the case most often called a gamma squeeze. The SEC staff examined it in its Staff Report on Equity and Options Market Structure Conditions in Early 2021, published on 14 October 2021. The report quotes GME closing at $347.51 on 27 January 2021 and reaching an intraday high of $483.00 the next day, prices as quoted in the report.

The staff reported that options trading in GME, measured by dollar volume, concentrated heavily in call options, many of them short-dated. But when it tested the gamma squeeze explanation, it wrote that it "did not find evidence of a gamma squeeze in GME during January 2021." Its reasons: the jump in options trading by individual customers, from $58.5 million on 21 January to a peak of $2.4 billion on 27 January, was mostly driven by more buying of puts, rather than calls, and market makers were buying call options rather than writing them. The staff wrote that these observations "by themselves are not consistent with a gamma squeeze."

The staff found that short covering played a part, but not the main one. Buying by traders with large short positions coincided with some of the sharpest price jumps, but it was a small fraction of overall buy volume, and the staff concluded that "it was the positive sentiment, not the buying-to-cover, that sustained the weeks-long price appreciation." Its summary: "a short squeeze did not appear to be the main driver of events, and a gamma squeeze less likely." The staff worked from regulatory data, including the Consolidated Audit Trail, which identifies the accounts behind trades and is not public. That gap is the point of the next section.

What Kresmion's gamma data can and cannot show

The live SPY panel on this page shows Kresmion's modeled dealer gamma exposure: net, call and put gamma, the zero-gamma flip level and the gamma call and put walls, explained in call and put walls. The gamma snapshot on Kresmion's greeks exposure tool is open without an account, and the walls and other greeks for every covered name open with a free account.

Every figure is computed from end-of-day open interest and signed by a stated assumption: dealers are net long the call side and short the put side. A gamma squeeze in the textbook sense is the case where that assumption is wrong for calls, because customers have been buying them and dealers are short, so the model would show that call leg as stabilizing when the hedging is amplifying. The tool's own assumptions block says that if the assumption is wrong for a name, that name's sign can flip. Open interest counts contracts outstanding and does not say who bought them, so modeled figures cannot confirm or rule out a gamma squeeze. They also come from prior-session open interest, so contracts opened and closed within one session never appear in them. Kresmion does not flag or forecast gamma squeezes. Its gamma data describes where modeled hedging is concentrated by strike under a stated assumption.

Key takeaways

Frequently asked questions

What is the difference between a gamma squeeze and a short squeeze?

A short squeeze is short sellers buying back shares to close losing positions. A gamma squeeze is options dealers buying shares to keep a hedge on calls they sold. Both add buying to a rising price and can happen together, but they come from different participants and stop for different reasons.

Why do short-dated options matter so much in a gamma squeeze?

An at the money option's gamma rises sharply as expiry approaches, so each short-dated contract near the price forces more rehedging per move than a longer-dated one. That gamma is concentrated in a narrow band around the strike, so the effect is strongest when the price is trading right at the strikes where the calls are open.

Was GameStop in January 2021 a gamma squeeze?

The SEC staff report of October 2021 said it did not find evidence of one. It found that the rise in individual customers' options trading was mostly driven by more buying of puts, rather than calls, and that market makers were buying calls rather than writing them. It also concluded that positive sentiment, not short covering, sustained the weeks-long rise.

Can dealer gamma data predict a gamma squeeze?

No. Modeled gamma exposure describes where hedging is concentrated under an assumption about who holds which side, and public open interest does not reveal who bought the calls. It describes the backdrop at a snapshot and says nothing about whether or when a stock moves.

How does a gamma squeeze end?

The hedging pressure fades as the options expire or lose delta through time decay, which releases the shares held as a hedge. It can end sooner if call buyers sell their contracts or the price turns lower, since short gamma hedging then sells into the fall.

This page is information, not investment advice.

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Source: U.S. Securities and Exchange Commission, Staff Report on Equity and Options Market Structure Conditions in Early 2021 (14 October 2021), sections 3.2, 3.4 and 3.9, https://www.sec.gov/files/staff-report-equity-options-market-struction-conditions-early-2021.pdf ; Cboe, S&P 500 Index (SPX) options product page, https://www.cboe.com/tradable_products/sp_500/spx_options/ ; closed form Black-Scholes greeks with illustrative inputs; Kresmion modeled dealer gamma exposure, with the assumptions stated on Kresmion's greeks exposure tool.

Kresmion Research.