What GEX measures
Gamma exposure totals the gamma options dealers carry across every strike and expiration — in effect, how much their combined delta would shift for a one percent move in the underlying. Where GEX concentrates, dealers must place large hedging trades to stay delta-neutral, and that hedging shows up as real, repeatable buying and selling pressure at specific prices.
Conceptually, gamma exposure at a strike is gamma times open interest times contract size times spot squared, scaled by one percent. The formula matters less than the intuition: it converts an abstract Greek into a concrete weight of forced trading sitting at each level of the terrain.
Two regimes
When dealers are net long gamma, they buy dips and sell rips — every move meets an opposing force. Ranges compress, price grinds and pins, and the ground holds firm underfoot.
When dealers are net short gamma, they sell into weakness and buy into strength — every move gets amplified instead of absorbed. Trends extend, air pockets open, and the terrain gives way. The boundary between the two regimes is the single most-watched level in this library.
The levels on the map
Zero gamma — the gamma flip — is the price where total dealer gamma crosses from positive to negative or back. Above it, hedging tends to calm the market; below it, hedging tends to chase it. Call Wall marks the strike carrying the most call gamma, usually overhead resistance; Put Wall marks its mirror below price, usually downside support.
A fourth level, the High Volatility Level, marks a price where a breach is projected to accelerate the move rather than absorb it — used as a breakout-confirmation filter rather than a target. All four levels move as positioning moves; they are read from bar magnitude, sign, strike concentration, and where the zero line gets crossed, and the effect is strongest during regular trading hours and close to expiration.