What Is Gamma Exposure?
Gamma exposure (GEX) is an estimate of how many shares market makers must buy or sell to stay delta neutral when price moves one point. It is not a prediction — it is a map of forced flow. Once you can read it, a lot of otherwise random intraday behaviour becomes mechanical.
Dealers are not taking a view
When you buy a call, someone sold it. That someone is usually a market maker who does not want directional risk, so they immediately hedge with shares. As price moves, the option's delta changes — that rate of change is gamma — and the hedge has to be adjusted continuously.
Long gamma dampens, short gamma amplifies
If dealers are net long gamma, their re-hedging sells rallies and buys dips: realized volatility compresses and price tends to range. If they are net short gamma, they must buy strength and sell weakness, which adds fuel to the move and expands volatility. Same market, opposite behaviour.
- Positive net GEX: mean reversion, tight ranges, fading extremes works.
- Negative net GEX: trend days, gaps that keep going, fading gets punished.
- The size of net GEX matters as much as the sign — small positive GEX is nearly neutral.
How the number is built
For each strike, GEX ≈ open interest x gamma x contract multiplier x spot, signed by an assumption about dealer positioning (dealers long calls sold to customers, short puts bought by customers). Summing across strikes gives net GEX; plotting it by strike gives the profile you see on the Gamma map.
What GEX is not
It is not a directional signal, it is not a guarantee of support, and it is stale the moment large new flow prints. Treat it as a conditional probability filter on top of your own thesis, refreshed intraday.
A worked example
Say SPY prints net GEX of +$3.2 billion per 1% move with the flip level at 512 and spot at 517. That combination tells you the market is in a positive-gamma channel: dealers sell into strength above spot and buy into weakness as price approaches 512, so a fade from 519 back toward 515 has flow behind it. If the same tape showed net GEX of -$1.1 billion with spot below the flip at 508, the read flips entirely — a break of 507 with dealers forced to sell into weakness is a continuation signal, not a level to buy.
- Positive $3B+ net GEX with spot well above the flip: expect compression and fade setups.
- Negative net GEX with spot below the flip: expect expansion, avoid fading the move.
- Always pair the sign of net GEX with the distance from spot to the flip level before sizing a trade.
Interactive: move spot and watch GEX change
Positive gammaDealers sell rallies and buy dips to stay neutral.
Volatility compresses. Ranges hold, extremes get faded back toward the middle.
Illustrative model for teaching only — the live profile on the Gamma map is computed from the real chain.
Key takeaways
- GEX estimates forced dealer hedging flow, not opinion.
- Positive gamma compresses volatility; negative gamma amplifies it.
- Always check the sign and the magnitude before choosing a strategy.
- A single net GEX number means little without the flip level and spot distance next to it.
Practice this in the terminal
FAQ
Do I need to compute GEX myself?
No. The Gamma map computes it live from the option chain; your job is interpretation and refresh discipline.
Which tickers give clean GEX?
Index products (SPY, QQQ) and mega-caps with deep chains. Thin chains produce noisy, unreliable profiles.
How large does net GEX need to be before I trust it?
There is no universal threshold, but as a working rule treat anything within about 20% of zero as a weak signal in either direction. Larger absolute values, especially several billion dollars per 1% move on an index product, indicate a regime that is more likely to persist through the session.
Can GEX flip sign intraday without a big news event?
Yes. Heavy 0DTE volume can shift the profile meaningfully within hours simply through expiring open interest and fresh positioning, so a morning read of the regime can be outdated by the early afternoon on expiration days.
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Educational content only. Options involve substantial risk and are not suitable for every investor. Nothing here is financial advice.