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Key Takeaways
- Zero gamma locates a price where aggregate GEX equals zero.
- A sign-changing zero crossing marks a gamma flip between positive and negative regimes.
- Find the crossing on the aggregate spot-price curve, then read the sign on each side.
- Reversing every position sign reverses GEX but preserves the zero coordinates.
- Use the selected crossing with the walls, options flow, and price structure to frame the trade.
What is zero gamma?
Zero gamma is a price where aggregate gamma exposure equals zero. It comes from recalculating the full option portfolio at hypothetical underlying prices, summing the signed contributions at each price, and locating the zeros of the resulting curve. A sign-changing zero crossing is a gamma flip, and the curve identifies the regime on each side: positive-gamma hedging trades against price changes, while negative-gamma hedging follows them.
How is zero gamma calculated?
Find two neighboring prices where aggregate GEX changes sign, then interpolate between them. Suppose aggregate GEX is −140 million in a consistent exposure unit at an underlying price of 4,440 and +160 million at 4,500. Linear interpolation places the crossing at 4,440 + 60 × 140 / 300 = 4,468.
Spot at 4,500 is 32 points above that crossing. In this example, the curve is positive above the crossing and negative below it. Read those signs from the calculated curve when evaluating another chain.
Formula
Zero gamma = underlying price S where aggregate dealer GEX(S) = 0- GEX(S) is the net gamma exposure evaluated at a hypothetical underlying price S, summing each contract gamma scaled by the 100-share multiplier, open interest, and a chosen move size across all strikes and expirations.
- A zero-gamma level is a price where the running sum equals zero. A crossing that also changes the sum’s sign is a gamma flip.
- Multiplying every signed exposure by −1 reverses the curve and preserves its zeros. Changing the relative positions, included contracts, volatility inputs, or time changes the curve itself and its crossings.
Worked Example
A gamma model evaluates net dealer GEX across a range of prices for an index trading at 4,500. It reads positive aggregate gamma at 4,500 and negative aggregate gamma at 4,440.
- At 4,500 the model sums net GEX to +160 million share-equivalents; at 4,440 it sums to −140 million.
- Interpolating linearly between those points, the curve crosses zero 28 points up from 4,440, so the modeled zero-gamma level is 4,468.
- Spot at 4,500 sits 32 points above 4,468, so the model reads the current regime as positive gamma with a 0.7 percent cushion to the boundary.
In this example, aggregate gamma is positive above 4,468 and negative below it. A move through the crossing changes the hedge response from trading against price to trading with it. Map the crossing alongside the walls, then connect the flow and technical structure to the position’s payoff.
Zero gamma vs the strike profile
The strike profile groups option exposure by strike. The aggregate spot-price curve reprices every included contract at each hypothetical underlying price. A crossing between neighboring strike bars does not calculate zero gamma. See the GEX selection and curve methodology, including strict spot comparisons and multiple crossings.
Display the selected aggregate crossing alongside the strike profile so the trader sees the regime boundary and the call and put concentrations together.
What moves the zero-gamma level
Changes to relative positions, included expirations, volatility inputs, and time reshape the curve. Multiplying every exposure by −1 flips the curve vertically but leaves its zero coordinates unchanged. Positive scaling, including a common unit conversion, also preserves the zeros.
Evaluate the full curve before selecting a level. Depending on the portfolio and evaluated price range, it has no crossing, one crossing, or several. Identify the crossing used by the product and read its surrounding signs.
How traders use zero gamma
Measure spot’s distance from the selected crossing, then connect the map with options flow and technical structure. For an open position, compare the next regime boundary with the planned exit and payoff. For a new trade, model the strike and expiration against the price scenarios around the level.
Zero gamma supplies the aggregate coordinate. The gamma flip describes the sign change. The strike profile supplies the concentrations. Together they organize the positioning read.
Limitations of zero gamma
- Scan the full curve for every crossing. A curve can have no zero, one, or several, so a single reported level can hide others, and a curve sampled on a price grid can miss two crossings that fall between sample points.
- Reprice between the samples to refine the crossing. Linear interpolation between two sampled prices approximates it.
- Confirm the sign convention before you read the regime. Reversing every position sign leaves the zeros in place but swaps the regime on each side, so the convention decides which side is positive gamma.
- Check each zero for a sign change. A point where the curve touches zero without changing sign is a zero-gamma level but not a gamma flip.
- Recalculate the curve after every open-interest update. Open interest updates after each session, and the model assigns who holds each contract.
Bottom line
Zero gamma is where the hedging regime changes sign, and the sign-changing crossing on the full curve is the gamma flip. Evaluate the whole curve, read the sign on each side of the crossing, and recalculate as positions, expirations, and volatility change.
Clear answers
Frequently Asked Questions
Sources and Further Reading
- Cboe: Market-maker gamma analysis and 0DTE market impact
- OIC: Understanding Options Greeks
- OIC: Open Interest - Why It Matters
How entries are sourced, calculated and updated: editorial methodology.