What is Gamma Exposure (GEX)?
Gamma exposure — GEX for short — measures how much dealers must buy or sell of the underlying index (here, SPX) as prices move, in order to stay hedged on the options positions they have written. Because market makers are the counter-party to most options trades, their aggregate hedging flow tends to become the marginal buyer or seller of the underlying, especially in the last hour of trading.
Positive GEX means dealers are net long gamma. As price rises they must sell into the move, and as price falls they must buy — a stabilizing, volatility-suppressing regime. Negative GEX inverts that flow: dealers chase price higher on the way up and add to the sell pressure on the way down, so intraday moves get amplified and trends persist.
How dealers hedge — and why traders watch it
When you buy a call, someone sold it. That seller (usually a market maker) is now short gamma; they must buy the underlying to stay delta-neutral, and buy more as price rises. That relentless buying is the machinery behind "gamma squeezes." The opposite is true when dealers are long gamma from short-dated puts: they buy dips and sell rips, pinning price to the strikes where their gamma is highest.
The reason traders watch the GEX chart is simple: the flip level between positive and negative gamma is where the market's reflexivity changes character. Above it, mean reversion tends to work. Below it, breakouts tend to stick. That's not a rule — it's a heuristic that shows up over and over in tape action.
How to read this chart
The top metrics tell you the four levels most GEX-informed traders track:
- Zero Gamma / Flip: the price where net dealer gamma crosses zero. Above = suppression. Below = amplification.
- Call Wall: the strike above spot with the largest positive call gamma. Acts as a magnet-ceiling on rallies.
- Put Wall: the strike below spot with the largest negative put gamma. Acts as a support-floor when it's been building.
- Vol Trigger: the lowest positive-gamma strike between the walls. Below it, hedging flow amplifies moves. Above it, hedging suppresses.
The bar chart underneath sorts the largest 12 net-GEX strikes by strike price. Green bars = net positive gamma (dealers pin toward this strike); red = net negative (dealers reject it). Big clusters of one color near spot are where the intraday tape tends to get sticky.
How this chart is calculated
The numbers on this page come from the full SPX options chain, refreshed every 25 seconds. For each strike we take gamma × open interest × 100 × spot, sign calls positive and puts negative (dealer perspective), then aggregate across the next eight expirations. This is the standard SpotGamma-style formulation — no proprietary smoothing, no vendor-locked feed. If you want to inspect the maths, the calculation lives in backend/app/services/gex_service.py in the open SquawkFlow repo.
Learn more
- What is Gamma Exposure (GEX)? A Complete Guide — Understanding gamma exposure and how dealer hedging creates support and resistance levels in the market.
- GEX Flip Price Explained: Where Market Volatility Regime Changes — The GEX flip price marks where dealer gamma transitions from positive to negative, fundamentally changing market behavior.
- Call Wall and Put Wall Explained: Options-Driven Support and Resistance — How call walls and put walls create real support and resistance levels through dealer hedging mechanics.
- Vol Trigger Explained: The SpotGamma Volatility Threshold — How the vol trigger level from SpotGamma signals shifts between low and high volatility environments.
- Gamma Squeeze Explained: How Options Drive Explosive Stock Moves — Understanding gamma squeezes, the mechanics behind them, and why GameStop (GME) was the ultimate example.