Options flow and GEX: reading SPX context to trade ES and NQ
The scale of the flow: the tail that wags the dog
The published numbers
A mechanism only matters if it has the size to weigh. The figures below are Cboe's and CME's, collected on August 17, 2026, not forum estimates:
The order of magnitude of the hedging need
Do the math with me, with a deliberately low assumption, flagged as such. If the average absolute delta of those 3.1 million 0DTE contracts is only 0.25, the hedging need is roughly 3.1M × 0.25 × 2 ES, about 1.5 million ES equivalents per day.
And it is not a one-off adjustment. Gamma forces it to start over at every move in price. Some hours, this flow is not a factor in your book: it is the dominant factor.
The rest of this lesson is for students
- Why 0DTE changes the nature of the phenomenon
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