Gamma Exposure
(GEX) Explained
GEX explains why markets sometimes pin to a strike for days and then suddenly accelerate. Understanding dealer gamma hedging turns this from mystery into a readable map of likely price behaviour.
Start with gamma itself
Gamma is the rate at which an option's delta changes as the underlying moves by one point. If a NIFTY call has a delta of 0.40 and a gamma of 0.005, a 1-point rise in NIFTY increases that call's delta to 0.405. Gamma is always positive for option buyers (long options) and negative for option sellers (short options).
ATM options have the highest gamma; deep ITM and deep OTM options have much lower gamma. Gamma also accelerates sharply as expiry approaches — a feature that makes it especially relevant for weekly NIFTY expiry traders. For a deeper foundation, see gamma explained.
What is Gamma Exposure (GEX)?
GEX (Gamma Exposure) aggregates the gamma of all outstanding option contracts in the market, weighted by lot size. In practical terms, it answers: if NIFTY moves by one point, how many rupees worth of underlying must dealers buy or sell to stay delta-neutral?
Market makers and dealers who sell options to retail and institutional traders are typically short gamma. To hedge their short option positions, they delta-hedge continuously — buying the underlying when it falls and selling when it rises. The size and direction of these hedging flows depend on their aggregate gamma exposure. When the number is large, dealer flows have a significant impact on price.
Positive gamma: the stabiliser
When dealers are net long gamma (they have bought more options than they have sold — positive GEX), their hedging behaviour dampens volatility:
- As NIFTY rises, their long calls gain delta → they sell futures/underlying to rebalance → price rise is slowed.
- As NIFTY falls, their long puts gain delta → they buy futures/underlying to rebalance → decline is cushioned.
In a positive gamma environment, you tend to see tighter intraday ranges, mean-reverting behaviour, and prices that struggle to trend cleanly in one direction. The market feels "sticky" around key strikes.
Negative gamma: the accelerator
When dealers are net short gamma (they have sold more options than they have bought — negative GEX), their hedging behaviour amplifies volatility:
- As NIFTY rises, their short calls lose delta → they must buy futures/underlying to rebalance → price rise is accelerated.
- As NIFTY falls, their short puts lose delta → they must sell futures/underlying to rebalance → decline is accelerated.
Negative gamma environments are associated with wider intraday swings, trending behaviour, and fast moves that can surprise traders relying on mean-reversion strategies. India VIX tends to be elevated when the market is in a negative gamma regime.
The gamma flip level
The gamma flip (or zero-gamma level) is the spot price at which aggregate dealer GEX transitions from positive to negative. Below this level, dealers are typically in a negative gamma position; above it, they shift to positive.
The gamma flip is a highly watched level by sophisticated options desks. When spot crosses the gamma flip upward, volatility often compresses as dealers switch from amplifying to dampening. When it crosses downward, volatility tends to expand. Knowing this level helps calibrate strategy selection: sell vol (straddles, iron condors) above the flip; be cautious with short vol below it.
A worked NIFTY example
Suppose NIFTY is near 22,500 (illustrative). Strike 22,500 has the largest call OI and put OI in the weekly series — the maximum open option concentration. Dealers who sold these straddles are short gamma at 22,500. Their hedging creates a pinning force: if NIFTY ticks above 22,500, they sell futures; if it ticks below, they buy futures. The result — a narrow range near 22,500 for most of the week.
On Wednesday, a global risk-off event causes NIFTY to drop sharply through 22,300. Below the gamma flip (say, 22,400), dealer gamma switches negative. Now falling prices cause dealers to sell more futures, which pushes prices down further. The 22,300-to-22,000 range is covered in a single session. The move that looked contained for three days suddenly turns violent — this is the negative gamma cascade that catches range-bound traders off guard.
A NIFTY lot size is 75. Even a 200-point move creates a ₹15,000 per lot swing. In a negative gamma regime, moves like this can happen in under an hour.
How to use GEX practically
- Above the gamma flip (positive GEX): Favour range-bound strategies like iron condors or short straddles. Expect mean-reversion behaviour. Time decay works well for option sellers.
- Below the gamma flip (negative GEX): Favour directional strategies or protective hedges. Avoid naked short options — moves can be faster and larger than SPAN margin accounts for. Consider buying options for defined risk.
- Near the flip level: Be cautious of both sides. The transition between regimes can cause abrupt volatility regime changes.
- Highest positive GEX strike: Acts as a gravitational magnet — similar to but distinct from max pain. Price often oscillates around it during the week before expiry.
Track GEX alongside open interest, PCR, and India VIX for the most complete view of the volatility regime. TradePulse's option chain analysis surfaces the OI concentration data underlying any GEX read.
Common mistakes when applying GEX
- Treating GEX as a buy/sell signal rather than a regime indicator — it tells you how the market might move, not necessarily when.
- Ignoring that retail-dominated markets (like NIFTY weekly near expiry) may have lighter dealer hedging than US equity indices — GEX effects are directionally similar but magnitude differs.
- Confusing strike-level open interest with dealer positioning — not all high-OI strikes represent dealer short gamma; some are retail buyer accumulation.
- Forgetting that gamma spikes near expiry — GEX signals are strongest in the 1–3 days before expiry and require recalibration for the next cycle.
Frequently asked questions
What is gamma exposure (GEX) in options?
GEX measures the total rupee amount of delta hedging that market makers must perform as the underlying moves by one point. It is calculated as the sum of gamma across all open contracts, weighted by lot size and open interest. GEX quantifies the forced buying or selling dealers will generate as the market moves.
What is positive vs negative gamma environment?
In positive gamma, dealers have bought options and must trade against market moves — stabilising volatility. In negative gamma, dealers have sold options and must trade with the market move — amplifying volatility and causing sharper, faster price swings.
What is a gamma flip or zero-gamma level?
The gamma flip level is the spot price at which aggregate dealer gamma transitions from positive to negative. When the market crosses this level, dealer hedging behaviour switches from dampening volatility to amplifying it — often causing a noticeable change in how quickly the market moves.
How does GEX relate to max pain?
Both GEX and max pain can identify price levels the market is attracted to near expiry, but they measure different things. Max pain is the strike where option buyers collectively lose the most. GEX describes real-time dealer hedging flows. GEX is more relevant intraday and during the week; max pain is more relevant in the final hours before expiry.
See open interest and regime data live
TradePulse's option chain displays the OI concentration, PCR and Greeks data that underlies any GEX analysis — free to explore.