Gamma Exposure
Research (GEX)
Dealer hedging is not passive. Understanding where market makers are long or short gamma reveals structural forces that shape NIFTY and Bank Nifty price behaviour every session.
What is Gamma Exposure?
Gamma Exposure (GEX) measures the aggregate gamma position that option market makers and dealers carry across the entire option chain, scaled by open interest. Gamma is the rate of change of delta — it tells you how fast a dealer's hedge must move as the underlying price moves. When you buy an option, someone on the other side — typically a dealer — sells it and then hedges the resulting delta. As price moves, that delta changes (driven by gamma), forcing the dealer to continuously adjust the hedge. GEX is simply the sum of those forced adjustments across every strike and expiry in the chain.
The math and intuition
For each strike, dealer GEX is estimated as:
GEX at strike = Gamma × Open Interest × Contract Multiplier × (±1)
The sign convention matters: dealers who have sold calls (and bought puts) are long gamma — their hedge requires buying into dips and selling into rallies, which dampens moves. Dealers who have bought calls (or sold puts) are short gamma — their hedge requires selling into dips and buying into rallies, amplifying moves. The net of all strikes is the aggregate GEX.
On NSE, retail and institutional participants predominantly buy options. Dealers absorb the other side, leaving them broadly short gamma for much of the options cycle. This is especially pronounced in the final days before weekly NIFTY or Bank Nifty expiry, when short-dated gamma is large and moves fast.
The Gamma Flip — the most watched level
The gamma flip is the underlying price level at which aggregate dealer GEX transitions from positive to negative (or vice versa). It is computed by interpolating across the GEX profile. When NIFTY or Bank Nifty trades above the gamma flip into positive GEX territory, dealer hedging flows act as a stabiliser — rallies get sold into by dealers re-hedging, dips get bought, compressing the range. When the index trades below the flip into negative GEX, dealer flows become pro-trend: drops accelerate because dealers must sell, bounces are sold faster. Experienced traders watch whether the index is holding above or has broken below the flip to gauge how much structural support exists in market-maker hedging.
Why it matters specifically for Indian index options
India's index options market is among the most active in the world by contract volume, with NIFTY 50 and Bank Nifty weekly contracts dominating. Several features make GEX particularly relevant here:
- Weekly expiry cycle. Gamma rises sharply in the final two sessions before Thursday (Bank Nifty) or the weekly NIFTY expiry. The GEX profile can shift dramatically in a single session near expiry, explaining sudden changes in intraday range dynamics.
- Retail-dominated option buying. Retail participants in India disproportionately buy calls and puts, pushing dealers into net short-gamma positions for much of the cycle. This structural short-gamma environment is why pre-expiry sessions can exhibit violent, fast-trending moves.
- High-OI strikes as friction zones. Strikes with very large open interest also have large absolute gamma exposure. These strikes often act as magnets (when GEX is positive) or as breakout zones (when GEX flips negative), making them essential reference points on the NIFTY option chain.
How TradePulse applies GEX
TradePulse computes the GEX profile from live NSE open interest data across all active strikes and near-term expiries. The platform identifies the net GEX per strike, the aggregate GEX sign, and the gamma flip level. This is surfaced alongside PCR, ATM IV, and max pain so traders can read structural hedging flows in context — rather than in isolation. Because GEX depends on gamma, which accelerates near ATM strikes and expiry, the reading is most meaningful in the 2–3 sessions before expiry when gamma is largest.
How a trader reads GEX in practice
There is no single trade that "GEX says buy." The practical use is contextual:
- Above the gamma flip, in positive GEX. Expect range compression and mean-reversion behaviour. Strategies that benefit from contained moves — iron condors, short straddles with defined risk — are structurally better suited to this environment. Breakouts tend to be faded quickly by dealer re-hedging.
- Below the gamma flip, in negative GEX. Expect amplified directional moves. Trending strategies, long options, or directional spreads may suit this environment better. Stop-loss levels become more important because dealer flows no longer cushion dips.
- At large-OI strikes with concentrated GEX. Watch for pinning action — where price gravitates toward a strike as expiry approaches — or for sharp moves if the level is breached with momentum, as dealers may need to re-hedge rapidly.
- Combine with OI and volatility. GEX alone is incomplete. A strike with large GEX but decaying OI (unwinding positions) has less structural weight. Pair GEX with OI changes, IV levels, and regime context for higher-quality reads.
Is GEX a precise forecast?
No. GEX describes the structural mechanics of dealer hedging — it does not predict what price will do. Markets move on sentiment, news, FII flows, and factors outside any model. GEX is best understood as a map of structural friction and amplification, not a signal. A trader who understands why a level is structurally important makes better decisions than one who treats any number mechanically as support or resistance.
How often does the GEX profile shift?
GEX changes continuously with every transaction that shifts open interest. Practically, it is most meaningful to re-read it at market open (using prior day's closing OI), after a significant OI build or unwind mid-session, and in the two days before expiry when gamma expansion changes the profile rapidly. TradePulse refreshes the underlying OI data on a short cycle so the GEX estimate stays current through the session.
Does GEX work equally for NIFTY and Bank Nifty?
The mechanics are identical, but the magnitudes differ. Bank Nifty options tend to have higher absolute gamma per strike due to the index's higher volatility and tighter weekly cycles. This means GEX-driven hedging flows in Bank Nifty can be more pronounced — intraday ranges in negative GEX environments are often sharper than in NIFTY. Both indices should be read with their own GEX profiles rather than applying one reading to the other.
Read the live GEX profile
TradePulse surfaces gamma exposure levels, the gamma flip, and high-OI structural strikes across NIFTY and Bank Nifty — updated through the session alongside open interest and IV.