core · Lesson 3
Gamma Exposure (GEX), explained
The single number that defines the regime. · 5 min read
GEX (Gamma Exposure) measures, in dollars per percent move, how much delta the dealer book gains or loses for each price tick.
For a single option: GEX ≈ gamma × open interest × spot² × contract multiplier. Summed across the whole chain, you get Net GEX.
Reading Net GEX
- Positive Net GEX: dealers are net-long gamma. Vol suppressed. Moves mean-revert.
- Negative Net GEX: dealers are net-short gamma. Vol amplified. Moves extend.
The Helios regime banner is based on this. POSITIVE_GAMMA = stay long structure / fade extremes. NEGATIVE_GAMMA = trade with the trend, momentum lives longer.
Bigger isn't always better. A modestly positive Net GEX with concentrated walls can be more impactful than a giant Net GEX spread evenly across strikes.
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