GEX Calculator: Gamma Exposure by Strike for SPX and 354 Stocks and ETFs
What a GEX calculator shows
Gamma exposure, GEX for short, is the estimated dealer hedging flow that a move in the underlying would trigger. A GEX calculator shows that exposure by strike so you can see where hedging is concentrated. It is a map of positioning, not a forecast and not advice.
How per-strike gamma is computed here follows the same dealer-perspective convention documented on the SPX GEX chart. The input is daily-settled open interest, not a tape of trades opened today. For every listed contract we take gamma times open interest times the 100-share multiplier times spot. Calls are counted positive and puts negative, the standard assumption that dealers are long customer-sold calls and short customer-bought puts. Open interest records that a contract exists. It never records which side a dealer holds, so every gamma figure, here and at every commercial vendor, inherits that assumption. Contracts opened and closed inside a single session never appear in settlement open interest, and the grid is rebuilt each session from the prior settlement.
Three levels sit on top of that grid. The call wall is the strike above spot with the largest positive call gamma, where dealer selling into a rally can slow the move. The put wall is the strike below spot with the largest negative put gamma. It is usually described as support, but the arithmetic does not give that: a desk short those puts sells into a decline rather than buying it, and what changes at the strike is that the puts go deep in the money, gamma collapses and the selling stops. The flip, also called zero gamma, is the price where net dealer gamma changes sign. Above it, hedging tends to dampen moves. Below it, hedging tends to amplify them. Those three numbers sum every expiration together. The gamma exposure heatmap keeps the expiration dimension so you can see whether the gamma sits in same-day expiries or further out, and the SPX gamma ladder draws each strike as a bar with the walls and the flip marked. For the mechanics behind the walls, read call wall and put wall explained. For how a ramp of gamma builds strike by strike, see the gamma ramp glossary entry.
Type a symbol above to open its gamma-by-strike table. SPX uses the dedicated index chart. Every other covered name opens the ticker page at the gamma section. Names that are not on the list show as not covered yet rather than a missing page. Use the featured row and the alphabetical list below to browse every covered name.
Gamma by strike is computed from daily-settled open interest. It is not real-time and it is not advice.
COMMON QUESTIONS
- What is a GEX calculator?
- A GEX calculator shows estimated dealer gamma exposure by strike. On SquawkFlow that figure is computed from daily-settled open interest, with calls signed positive and puts negative from the dealer perspective. It is a map of where hedging would concentrate, not a forecast.
- How often does it update?
- Each session, from the prior open interest settlement. The grid is not real-time. Contracts opened and closed inside a single session never appear in settlement open interest.
- Which symbols are covered?
- SPX on the dedicated index chart, plus every US stock and ETF on the SquawkFlow ticker list, 354 names. Unknown symbols stay on this page as not covered yet rather than opening a missing ticker page.