Gamma exposure, explained
Read modeled exposure beside price, with its limits in view.
In this article 8 sections
What GEX measures
Gamma measures how an option’s delta changes per $1.00 underlying move. GEX combines gamma, contract counts, contract size and an assumed position sign.
The result depends on the selected contracts, inputs and timestamp. It models exposure; it does not reveal dealer inventory.
Sources: Options Industry Council (OCC): Gamma.
A gamma flip under review
Compare QQQ’s completed closes with its short-horizon flip.
Choose a checkpoint for 1-minute detail. Later prices stay hidden.
A flip crossing alone is not an entry.
Historical review. Plans are hypothetical; fills, delivered signals and a trading edge are not proved.
- Context
- Preopen walls: call $720.00, put $705.00. Flips: ≤1 DTE $717.91; ≤7 DTE $717.98. ≤1 DTE is not 0DTE-only. The 15-minute-delayed model was stale; alerts were suppressed. Pause until model timing and a fresh broker quote are verified. No order was authorized.
- Wait for
- The 09:55–09:59 block closed $718.88 above the short-horizon flip, known at 10:00 ET. This is an observation, not an automatic entry.
- Execution
- No order is specified or executed. Define entry, invalidation and risk separately using fresh quotes and acceptable spreads. Shorts require borrow; size must fit buying power. No option or futures trade is inferred.
- Invalidation
- A completed close back below the same flip challenges the hold-above idea. Keep the horizon fixed.
- Management
- Follow completed closes. Wait for any separately required wall touch. If no condition qualifies, staying out is valid.
Above at 09:56 ET; back below at 10:17. The session had 12 strict adjacent-close crossings; neither primary wall was touched. No entry, alert, fill, edge or P&L is established.
Source, timestamps & selection
- Candles
- Databento XNAS.ITCH · venue OHLCV, not consolidated SIP volume. These are venue bars, not a consolidated market tape.
- Model source
- Tradier sandbox · original archived native model. Source delay: 900 seconds.
- Model built
2026-09-09T06:40:02.007023+00:00- First recorded
2026-09-09T06:44:08.998656+00:00- Open interest timestamp
- Unknown. No point-in-time open-interest clock was supplied.
- Evidence limit
- A local producer cycle recorded this model before the cash open. The producer log is mutable and has no independently sealed receipt. The first and selected records report stale=true and alerts_suppressed=true; no enabled alert, trader broadcast or execution is proved. Exact OI availability is unknown. The chart uses a different price provider. Bar-end times are the earliest theoretical observation times after a minute closes, not proven client delivery times.
- Why this day
- Four editorial examples selected after reviewing all 12 SPY/QQQ/IWM sessions from September 8–11, 2026. Hindsight selection is explicit. Untouched levels, recrossings and the invalidation-first case remain visible; no hit rate or predictive performance is claimed.
The producer record is mutable. “First recorded” describes the recorded archive; it is not proof that a trader received the same levels at that instant.
Archive fingerprints
- resource-case-study-census.json
af9379d9eb6802044356957fd6cf9a96b203eb57bddafd844c2d56ebf679de85 - cycles.parquet
774e0b67dd965b652f12ef1f7a5e90a49a81ba14871c05f2851144a24731b7a2 - contracts-QQQ.parquet
0ad36606577cb7693b97c4538fcfd12b70c99d7e1e2831c7a10d427fc86822db - QQQ-preview.json
61590fe909b65c86fcac3ef1642b45a9032f2cc6558cff5d812cd4d44520faa7
Explore the concept with a simplified model
The dollar GEX formula
Signed GEX = gamma × open interest × multiplier × price² × 0.01 × assumed sign. Add the contract contributions to get net GEX.
This convention expresses the dollar change in delta-equivalent shares for a 1% underlying move, valued at the starting price. It is not premium, volume or P&L. A per-$1.00 measure uses different scaling.
Standard ETF contracts generally represent 100 shares. Verify adjusted deliverables or exclude them.
Sources: Cboe: Equity Options Product Specifications; Cboe DataShop: Frequently Asked Questions.
A quick example
Fictional ETF: price $100.00, gamma 0.02, open interest 1,000, multiplier 100. A 1% move is $1.00: 0.02 × 1,000 × 100 × $1.00 = 2,000 delta-equivalent shares, worth $200,000.00.
The assumed sign makes that +$200,000.00 or −$200,000.00 per 1% move. Contract counts do not establish dealer direction. This illustration holds gamma constant; actual gamma changes with price, time and volatility.
Positive does not mean bullish
A hedged long-gamma position may sell rises and buy falls; a short-gamma position may do the reverse. Actual price effects depend on inventory, hedging and liquidity.
Long calls and long puts both have positive gamma. Assigning puts a negative sign is an inventory assumption. Cboe’s SPX 0DTE study also distinguishes gross activity from net market-maker risk; its finding is sample-specific.
Sources: Options Industry Council (OCC): Gamma; Cboe — Mandy Xu: Much Ado About 0DTEs: Evaluating the Market Impact of SPX 0DTE Options.
Read it beside price
Use concentrations, sign changes and expiry differences as reference points.
- Compare price with exposure concentrations.
- Compare the nearest expiry with a wider window.
- Keep the model timestamp visible.
How this sits in a plan you already have
Prism plots modeled exposure next to price so you can locate entry and invalidation against the current book. It does not choose the trade, predict direction, or produce a return.
- Wait for price at an exposure concentration instead of chasing through the middle of the range.
- Place the stop beyond that structure instead of an arbitrary tick count.
- Recheck the expiry window before treating one concentration as the only one that matters.
- If the data clock is not current, stand down. A demo or stale book is not a live book.
What remains unknown
Open interest does not show who owns each contract, when it opened or how it is hedged. A level cannot guarantee a reversal, volatility or direction.
Check price structure, liquidity and event risk before applying your own risk plan.
Sources and editorial notes
Read the primary references and editorial policy
Published by GEXfreak. Prism by GEXfreak is the product described in these guides. Definitions reference the primary sources below; examples and tool-selection checklists are GEXfreak’s own illustrations. This is product education, not independent investment research.
These sources explain options mechanics and data. They do not endorse Prism or validate the predictive value of its levels. Undated pages are marked below; the checked date is when the source was reviewed.
- Gamma — Options Industry Council (OCC). Publication date not stated. Checked .
- Equity Options Product Specifications — Cboe. Publication date not stated. Checked .
- Frequently Asked Questions — Cboe DataShop. Publication date not stated. Checked .
- Much Ado About 0DTEs: Evaluating the Market Impact of SPX 0DTE Options — Cboe — Mandy Xu. Published 2023-09-08. Checked .
For the product’s calculation and data boundaries, read Prism’s methodology.
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