What is GEX (Gamma Exposure)?
GEX, or gamma exposure, measures the total gamma that options dealers (market makers) are holding, expressed in dollars per 1% move in the underlying. Because dealers hedge their options books by buying and selling the underlying, their aggregate gamma position quietly shapes how price behaves — where it gets pinned, where it accelerates, and which strikes act as support and resistance. Reading gamma exposure is like seeing the market's hidden terrain before price reacts to it.
When net GEX is positive (dealers are long gamma), hedging leans against price: rallies get sold and dips get bought, so the market tends to chop and mean-revert. When net GEX is negative (dealers are short gamma), hedging chases price: moves get amplified into trends and volatility expands. The price where that balance flips sign is the gamma flip (zero gamma) — the most important line on the chart.
MRXgamma computes GEX in real time from the live options chain for SPX, SPY, QQQ and single stocks, and turns it into tools traders actually use: a per-strike gamma exposure profile, a gamma heatmap across every strike and expiration, options inventory, higher-order greeks (delta, vanna and charm), and a live options flow tape. Each section below explains one piece and how to trade it — especially for fast-moving 0DTE (zero-days-to-expiration) options on SPX.
The Gamma Flip (Zero Gamma)
The gamma flip — also called zero gamma — is the price where dealers' net gamma exposure changes sign. It's the single most important line on the chart because it tells you what kind of day to expect.
Above the flip: dealers are usually long gamma. Their hedging leans against price, so moves get dampened — think chop, mean-reversion and pinning.
Below the flip: dealers are usually short gamma. Their hedging chases price, so moves get amplified — think trending, momentum and higher volatility.
- Spot above γ-flip → expect range / mean-reversion
- Spot below γ-flip → expect trend / volatility expansion
- A break through the flip often changes the character of the whole session
Positive vs Negative Gamma (Gamma + / −)
Net GEX has a sign, and that sign is the market's volatility regime.
Positive / long gamma (+) means dealers dampen moves. Rallies get sold, dips get bought — price tends to revert toward high-gamma strikes. Great for range and fade setups.
Negative / short gamma (−) means dealers amplify moves. Rallies force more buying, dips force more selling — price tends to trend and accelerate. Great for momentum, dangerous for fading.
- Green bars = positive gamma at that strike (stabilizing)
- Red bars = negative gamma at that strike (destabilizing)
- Net GEX sign sets your whole game plan for the session
The Gamma Heatmap
The heatmap maps gamma exposure across every strike and expiration at once. Instead of reading one chart, you see the entire options surface as a grid of color.
Bright green cells are heavy positive-gamma zones — the walls that act as magnets and resistance. Bright red cells are heavy negative-gamma zones — where moves can accelerate. Tags like CW (call wall), +GEX and ATM mark the levels that matter most.
- Find gamma concentration clusters instantly
- See how walls build or decay across expirations
- Spot the magnets price is likely to gravitate toward
Options Inventory (OI)
Options inventory shows the open interest sitting at each strike — the actual positions dealers must hedge. Where inventory is stacked, hedging pressure is strongest.
Reading inventory next to gamma tells you why a level matters: a big call wall with heavy inventory is a stronger magnet than gamma alone suggests. Toggle 5-minute vs all-day to see fresh positioning versus the standing book.
- Call vs put inventory at every strike
- 5-minute view = today's fresh positioning
- All-day view = the standing book dealers must hedge
Using Delta or Gamma (and Vanna & Charm)
MRXgamma lets you view exposure through different greeks, each answering a different question:
Gamma — how aggressively dealers must hedge as price moves. This is the pin/acceleration lens.
Delta — the directional exposure dealers carry, useful for gauging directional pressure.
Vanna & Charm — how hedging shifts as volatility and time change; the slow currents that drive drift into expiration and around events.
- Gamma → pinning & acceleration around strikes
- Delta → net directional pressure
- Vanna/Charm → vol- and time-driven drift (great for 0DTE)
Options Flow (Live Tape)
Options flow is the live tape of executed options trades. Every print shows the strike, call/put, side, size, premium, and whether it was a single, a split, or a large block.
Flow reveals where real capital is positioning right now — big premium hitting the ask, repeated sweeps in one strike, or a block trade can front-run a move that gamma alone won't show. Combined with GEX, flow tells you both the terrain and the traffic.
- Live prints: size, premium, side, DTE
- Block & sweep tags highlight institutional size
- Flow bias confirms or fades the gamma picture
