Gamma Exposure (GEX)¶
OVERVIEW¶
Gamma exposure (GEX) measures the cumulative gamma position that options market makers hold across every strike and expiration on a given underlying. Because dealers run a delta-neutral book, their gamma position dictates how many shares they must buy or sell as the underlying moves to stay hedged.
GEX is reported in dollars per 1% (or per 1-point) move and tells traders whether dealer hedging will dampen volatility (positive GEX) or amplify it (negative GEX). It is one of the most-watched flow metrics on Tapeboard's options dashboards and a core input for regime-aware traders.
| Net GEX Sign | Dealer Behavior | Market Effect |
|---|---|---|
| Positive (+) | Buy on drops, sell on rallies | Mean-reverting, volatility compression |
| Negative (−) | Sell into weakness, buy into strength | Trend-amplifying, volatility expansion |
| Zero (flip level) | Neutral pivot point | Gravitational strike on expiration days |
Note
The strike where net GEX crosses zero is called the gamma flip level — often the most important strike on the board and a key reference in Tapeboard's options dashboards.
HOW IT WORKS¶
Dollar Gamma Formula¶
For a single option contract, dollar gamma is calculated as:
| Variable | Definition |
|---|---|
| Γ | Option's gamma |
| Open Interest | Number of open contracts |
| 100 | Standard contract multiplier |
| S | Current spot price |
| 0.01 | Scalar for a 1% move |
Net GEX Aggregation¶
Net GEX is aggregated across the full options chain using the standard dealer positioning assumption — dealers are short calls and long puts:
Scaled by spot² × 0.01 to express the result in dollar terms per 1% move.
Note
The "dealers short calls, long puts" assumption reflects dominant retail flow. This assumption can break down during periods of heavy institutional call buying or covered-call ETF growth. See Limitations below.
WORKED EXAMPLE¶
Scenario: SPY trades at $520 on May 5, 2026.
The 520-strike calls expiring in 14 days carry:
| Parameter | Value |
|---|---|
| Gamma (Γ) | 0.038 |
| Open Interest | 62,000 contracts |
| Spot Price (S) | $520 |
Dollar gamma at that single strike:
Full chain aggregate scenarios:
| Net GEX | Dealer Hedging Flow | Expected Behavior |
|---|---|---|
| +$2.1 billion | Sell ~$2.1B per 1% rally, buy ~$2.1B per 1% drop | Compressed realized volatility |
| −$1.5 billion | Sell into drops | Accelerated downside, expanding VIX |
FEATURES¶
Tapeboard surfaces GEX across three primary use cases:
Regime Identification¶
| GEX Regime | Favored Strategy |
|---|---|
| Positive GEX | Mean-reverting intraday plays, fade extremes, sell straddles |
| Negative GEX | Trend-following, breakout strategies |
Gamma Flip Mapping¶
The zero-cross strike acts as a gravitational pivot. Markets frequently pin to this level on expiration days. Tapeboard plots the gamma flip level directly on the options chain and intraday price view.
Squeeze Setup Detection¶
When call gamma builds at out-of-the-money strikes and price approaches them, dealer hedging buys can fuel a gamma squeeze. Tapeboard flags these buildups in the flow dashboard.
Tip
Combine GEX squeeze signals with unusual options activity and delta-adjusted open interest to confirm setup conviction before entering a position.
LIMITATIONS AND MISCONCEPTIONS¶
Note
GEX is an estimate, not a direct measurement. Dealer positioning is not publicly disclosed.
| Limitation | Detail |
|---|---|
| Assumption risk | The short-calls / long-puts assumption breaks during heavy institutional call buying or covered-call ETF flows (JEPI, QYLD, XYLD), which can flip dealers long calls |
| Listed options only | OTC bilateral structures and structured products carry their own dealer hedges that never appear in the data |
| No directional bias | Negative GEX means higher volatility potential — it is not inherently bearish |
| Greek completeness | GEX models ignore vanna and charm, which drive significant flow around expiration |
Tip
Use GEX alongside vanna and charm metrics on Tapeboard to get a more complete picture of dealer hedging flows, especially in the final days before major expirations.