What is Gamma Exposure?
Gamma exposure (GEX) measures the total amount of gamma risk that options market makers hold across all strikes and expirations for a given underlying asset. It quantifies how much market makers need to buy or sell the underlying stock or index as prices move, creating a powerful feedback loop that can either stabilize or destabilize the market.
To understand GEX, you first need to understand gamma itself. Gamma is the rate of change of an option's delta with respect to a one-dollar move in the underlying price. When market makers sell options to retail and institutional traders, they delta-hedge their exposure by buying or selling shares of the underlying. As the price moves, their delta changes, and gamma tells them how fast that delta is shifting.
How GEX Creates Support and Resistance
When aggregate GEX is positive, market makers are "long gamma." This means that as the price rises, their delta becomes more positive, forcing them to sell shares to stay hedged. As the price falls, their delta becomes more negative, forcing them to buy shares. This creates a natural dampening effect: market makers sell into rallies and buy into dips. Positive GEX environments tend to produce low-volatility, mean-reverting price action.
When aggregate GEX is negative, the opposite occurs. Market makers must buy into rallies (chasing price higher) and sell into declines (accelerating the drop). Negative GEX environments are associated with higher volatility, trending moves, and the potential for violent swings. The February 2018 Volmageddon and the March 2020 COVID crash both occurred in deeply negative GEX environments.
Key GEX Levels Every Trader Should Know
Call Wall: The strike with the largest positive gamma from call options. The standard convention (the one this calculation uses) signs call gamma positive, meaning dealers are assumed long gamma there. A long-gamma desk sells into strength to stay delta-neutral, and that selling is the headwind that can cap upside moves.
Put Wall: The strike below spot with the largest put gamma, usually described as a support floor. The delta math does not actually mirror the call wall, and this is where most explanations go wrong. A short put has positive delta that grows as spot falls, so a dealer short puts sells into the decline, amplifying it rather than supporting it. The level still tends to matter, but through different mechanisms: gamma collapses once price trades through the strike, so the selling pressure simply stops, and holders closing protection near the strike mechanically buy back the dealer's short stock.
GEX Flip (Zero Gamma Level): The price at which aggregate gamma transitions from positive to negative. Above the GEX flip, markets tend to be calmer and mean-reverting. Below it, expect more volatile, directional moves. Many traders use the GEX flip as a critical line in the sand for position sizing and strategy selection.
How to Use GEX in Your Trading
Start by checking the GEX profile before the market opens. If the S&P 500 is trading well above the GEX flip with a nearby call wall, expect a range-bound day, ideal for selling premium or mean-reversion strategies. If the index is below the GEX flip with thin gamma support, prepare for trending conditions and wider stops.
Watch for shifts in GEX throughout the week. Large options expirations (monthly OPEX, quarterly OPEX) can dramatically change the gamma landscape as contracts expire and roll. The days leading into and following OPEX often see regime changes in volatility.
How SquawkFlow Displays GEX Data
SquawkFlow publishes the call wall, put wall, and GEX flip computed from daily-settled Cboe open interest. The levels do not update from intraday options trades, and dealer positioning remains a model assumption rather than an observable. Each published level carries its open interest settlement date.
Understanding GEX transforms how you read the market. Instead of guessing at support and resistance, you can see exactly where the mechanical flows from dealer hedging will kick in.