Synthetic GEX profile with a zero crossing at $100

# Gamma exposure and gamma squeezes Canonical: https://halfonadouble.com/learn/gamma-exposure Data through: 2026-10-16 close Publisher: Half on a Double **Gamma exposure (GEX) summarizes how an options portfolio's delta changes as the underlying price moves.** A public GEX estimate depends on its position assumptions, expiration coverage, observation date and units. It does not directly reveal dealers' actual holdings. Delta measures an option's price sensitivity to the underlying; gamma measures how that delta changes. A long vanilla call and a long vanilla put both have positive gamma. Short positions have negative gamma. [OIC's gamma guide](https://www.optionseducation.org/advancedconcepts/gamma). ## Positive and negative gamma: what the sign means For a portfolio whose holder maintains a delta hedge: | Portfolio gamma | After the underlying rises | After it falls | | --- | --- | --- | | Positive / long gamma | Reduce the hedge's long exposure | Increase the hedge's long exposure | | Negative / short gamma | Increase the hedge's long exposure | Reduce the hedge's long exposure | Those adjustments can counteract or reinforce market moves. Their actual effect depends on net inventory, offsets and available liquidity. They do not guarantee mean reversion or a trend. [Cboe's analysis of gamma hedging](https://www.cboe.com/insights/posts/volatility-insights-evaluating-the-market-impact-of-spx-0-dte-options/) explains the distinction between trading activity and net market-maker risk. This site's signed GEX convention assigns **calls positive and puts negative**. That is a modeling assumption about positions, not a statement that put options intrinsically have negative gamma. Open interest alone cannot establish which side of a contract a dealer owns. ## How to read a gamma exposure chart This **synthetic illustration was prepared October 5, 2026**. Its values are invented to explain the axes; they do not come from a real option chain or the site's pricing implementation. Calls are assigned positive exposure and puts negative. The vertical axis is **millions of dollars of delta change per $1 underlying move**. The horizontal axis is a hypothetical underlying price, not an option's strike.

Illustration only: the modeled sign changes at $100. Values and interpretation are also provided in the table below.

| Hypothetical underlying price | Synthetic GEX ($ millions per $1 move) | Reading | | --- | ---: | --- | | $90 | −2.0 | Negative modeled exposure | | $95 | −1.0 | Negative modeled exposure | | $100 | 0.0 | Sign crossing: this example's gamma flip | | $105 | +1.0 | Positive modeled exposure | | $110 | +1.5 | Positive modeled exposure | The **gamma flip**, also called a zero-gamma level, is a price where the signed exposure changes sign. In this illustration the positive region is above $100. That orientation is not universal: a different profile can have the opposite orientation, multiple crossings or no crossing. Zero exposure also does not mean that all other market risks vanish. ## Call walls and put walls use a different axis A wall refers to an **option strike**, whereas the curve above varies the hypothetical underlying price. This second invented example shows side-specific contributions at a fixed underlying price of $100, using the same units and sign convention: | Option strike | Call contribution ($ millions per $1 move) | Put contribution ($ millions per $1 move) | | --- | ---: | ---: | | $95 | +0.2 | **−0.8: put wall** | | $100 | +0.4 | −0.5 | | $105 | **+0.9: call wall** | −0.2 | The call wall is the largest call contribution; the put wall is the largest put contribution in absolute size. Here they are $105 and $95. All six contributions sum to zero, consistent with the illustrated flip at $100. Neither label establishes resistance, support or a known order waiting to trade. Different providers can use different definitions, so check scope before comparing wall levels. ## GEX flip versus gamma max | Published reference | Meaning | | --- | --- | | Net GEX | Signed gamma exposure at the snapshot's underlying close | | GEX flip | A confirmed sign crossing in that model | | Call / put wall | The strike with the largest respective side-specific GEX magnitude | | [Gamma max](/learn/gamma-max) | A separate model reference associated with peak aggregate gamma | Gamma max is not interchangeable with a GEX flip or the largest absolute value of a signed GEX curve. Read each published field according to its own definition. A missing confirmed flip means the site has no qualifying value to publish; it does not mean the level is zero. ## Check units before comparing numbers The main **Net GEX** field on ticker pages is dollar-delta change per **$1 underlying move**, under the calls-positive / puts-negative convention. Other providers, and this site's advanced GEX summaries, can quote exposure per **1% move** instead. The two units are different. Normalizing a figure per 100,000 open contracts adds another comparison scale; it does not remove the need to check the underlying move unit. Always compare the same date, expiration scope, units and position assumptions. End-of-day estimates cannot show all of the positions opened, closed or hedged during a later session. ## What is a gamma squeeze? If dealers are short gamma and hedge with the underlying, a rise can prompt buying that reinforces the rise. This possible feedback mechanism is often called a gamma squeeze. Establishing that it happened requires evidence of positions and trading, not simply a sharp rally or large call volume. GameStop in January 2021 is often invoked as an example, but SEC staff reported that the available data did **not** establish a gamma squeeze during that period. [SEC staff report, page 29](https://www.sec.gov/files/staff-report-equity-options-market-struction-conditions-early-2021.pdf). ## Read the current published references The [SPY options snapshot](/stock/SPY) and [GME options snapshot](/stock/GME) show net GEX, confirmed flip when available, and call/put wall levels beside the snapshot's date. The [GEX extremes screen](/screens/gex-extremes) compares exposure normalized to 100,000 open contracts. These are derived references under stated assumptions, not observations of dealer inventory. For historical price and published reference levels, use the [stock chart](/chart). That history is distinct from the synthetic GEX profile above. The [methodology](/methodology) describes the public fields and their limitations. ## Related [Open interest](/learn/open-interest) · [Gamma max](/learn/gamma-max) · [Max pain](/learn/max-pain) · [All learning guides](/learn)