GEX, Zero Gamma & Walls

Gamma Exposure (GEX) is the rate at which dealers must trade the underlying for each $1 move in price. It's the engine behind most intraday flows.

Net GEX

Sum of (gamma × open interest × spot²) across all options. Positive net GEX = dealers are long gamma — they sell into rallies and buy dips, which dampens volatility. Negative net GEX = dealers are short gamma — they buy into rallies and sell dips, which amplifies moves.

Zero Gamma (ZG)

The price level where net GEX flips from positive to negative (or vice versa). Above ZG, the market is typically calm; below ZG, vol expands. ZG often acts as a soft pivot — many trend changes happen right around it.

Walls & Floor

• Call Wall: the strike with the largest concentration of call gamma. Acts as resistance — when price approaches, dealer hedging tends to push it back.
• Put Floor: the strike with the largest concentration of put gamma. Acts as support — dealer hedging absorbs sell-pressure here.
• Magnet: the strike with the absolute highest gamma. Price tends to gravitate here, especially into expiration.