GEX Explained: Gamma Exposure and Order Flow
GEX (gamma exposure) estimates how options positions change their delta as the underlying moves. A dealer GEX model adds assumptions about who holds those positions. Use it as context for orderflow trading, with the model, units and data timestamp visible.
Senzoukria · Learn · Updated 13 September 2026
What gamma exposure measures
Gamma measures how delta changes with the underlying price. Long calls and long puts have positive gamma; short positions have negative gamma. The Options Industry Council explains the Greek. The sign of dealer exposure is a separate positioning question.
Open interest counts outstanding contracts, each with a long and a short side. It does not identify which side a dealer holds. Assigning positive exposure to calls and negative exposure to puts is a modeling assumption, not a measurement of all dealer positions.
GEX calculation: formula, units and example
For gamma expressed per unit of underlying price, a common convention estimates the change in delta-equivalent dollar exposure for a 1% move:
GEX_1% = Σ(position sign × gamma × contracts × multiplier × spot² × 0.01)
Use actual signed positions when known. Substituting open interest requires explicit position assumptions. Contract multipliers and adjusted contracts matter. Dollar gamma per $1 move and dollar gamma per 1% move are different units.
| Input | Value |
|---|---|
| Underlying price | $100 |
| Gamma per $1 | 0.02 |
| Assumed long position | 1,000 contracts |
| Multiplier | 100 |
| GEX per 1% move | +$200,000 |
The arithmetic is 0.02 × 1,000 × 100 × 100² × 0.01. A 1% rise is $1 here: holding gamma locally constant, delta changes by 2,000 underlying units, worth $200,000 at the starting spot. An identical short position reverses the sign. This is neither premium paid nor a forecast of money entering the market. Larger moves require recalculating Greeks.
GEX calculation and its impact on order flow
Under a delta-neutral hedging assumption, a long-gamma book tends to require selling after a rise and buying after a fall. A short-gamma book reverses that relationship. The model does not reveal when, where or through which instrument a hedge actually occurs.
- Record source, chain timestamp, expiry selection and position assumptions.
- Mark a modeled level and explain its mapping to the instrument you trade.
- Read executed volume and price response in the orderflow footprint.
- Compare executions with resting liquidity on the heatmap.
- Record observations that contradict the hypothesis, not only those that agree.
A positive estimate does not guarantee a range; negative exposure does not guarantee a trend. A footprint cannot identify a print as a dealer hedge merely because it occurs near a gamma level.
These illustrations demonstrate a conditional model and a synthetic profile, not live levels.
Zero gamma, call walls and put walls
A zero-gamma level is a root of a chosen exposure curve. There may be several roots or none in the evaluated range. Recalculating gamma as spot changes differs from holding current gamma fixed. Gamma walls depend on the selected metric: concentrated open interest is not necessarily concentrated gamma or guaranteed support.
GEX for ES and NQ futures
SPX, SPY and ES have different price scales and contracts; so do NDX, QQQ and NQ. An ETF strike is not the same numerical futures price. Record the conversion, futures basis and observation time. Prefer a matching underlying and chain when the source supports it.
Why dashboards disagree
- Different expiry selections, especially 0DTE versus all expiries.
- Different position signs, open-interest snapshots and contract multipliers.
- Different spot, volatility, rates, units or treatment of missing quotes.
Near expiry, small changes can change gamma quickly. Delayed inputs remain delayed; open interest is not an intraday options flow tape. Compare like-for-like methods before comparing headline totals.
Explore and test
The Senzoukria GEX dashboard places options context beside order-flow tools. Website demonstrations are simulated. Use the futures backtesting guide to specify a rule, costs and rejection criteria before treating an observation as an edge.
Frequently asked questions
- What is GEX in trading?
- Gamma exposure scales option gamma by position size to estimate changes in delta. Public dealer GEX models generally infer positioning rather than observing every dealer position or hedge.
- How is GEX calculated?
- One dollar-gamma convention for a 1% move is signed gamma × contracts × multiplier × spot squared × 0.01, summed across options. Position signs and units must be stated; call or put type alone does not establish the sign of a dealer position.
- Does GEX predict market direction?
- No. Hedging models are conditional on positions, volatility, expiry coverage and data freshness. Other flows and news can overwhelm the modeled effect. Compare the hypothesis with actual executions and price response.