Rate of change of Delta for a ₹1 move in the underlying.
Quick answer: Gamma measures how fast Delta changes when the underlying moves — it is the acceleration behind an option's directional exposure, and it peaks for at-the-money options close to expiry.
Simple explanation
If Delta is your speed, Gamma is your acceleration. A high-Gamma option sees its Delta change quickly as Nifty moves, so a position that was mildly directional can suddenly become strongly directional. Gamma is highest for at-the-money options and explodes in the final days before a weekly expiry.
Gamma — visual
How Gamma behaves
Gamma peaks sharply at the at-the-money strike and falls toward zero for deep in- or out-of-the-money options. The peak grows taller as expiry approaches.
Measures
Rate of change of Delta for a ₹1 move in the underlying
Sign
Long options +Γ (buyers) · Short options −Γ (sellers)
Typical range
Always positive for long options; largest ATM, near zero deep ITM/OTM
Order
Second-order
Detailed explanation
Why Gamma matters
Gamma is the second derivative of the option price with respect to the underlying, or equivalently the first derivative of Delta. It tells you how much your Delta — your directional exposure — will change after the next move. Buyers of options are 'long Gamma': their positions get more profitable-directional as the market moves their way and less exposed as it moves against them, a favourable curvature. Sellers are 'short Gamma' and face the opposite: their losses accelerate.
The expiry-day Gamma spike
Gamma concentrates at the ATM strike and rises dramatically as time to expiry shrinks. On Nifty and Bank Nifty weekly expiry days, ATM options have enormous Gamma — a 30-point move can flip an option from 0.4 to 0.6 Delta in minutes. This is why selling naked ATM options into expiry is so dangerous: a small adverse move produces an outsized, accelerating loss.
Gamma scalping
Long-Gamma traders can 'scalp': they hold options and trade the underlying against the changing Delta, buying dips and selling rips that Gamma forces on them, harvesting the movement. The cost of being long Gamma is Theta — you pay time decay for the privilege of favourable curvature. Gamma and Theta are the eternal trade-off.
Short Gamma risk in income strategies
Iron Condors, short straddles and short strangles are all short Gamma. They earn Theta while the market is calm but bleed quickly if it trends, because Gamma makes the losing side's Delta grow faster than the winning side's shrinks. Managing short-Gamma risk — sizing small, adjusting early — is the core skill of a premium seller.
Formula
Gamma formula
Γ = n(d₁) / (S · σ · √T)
n(d₁) is the standard-normal probability density. Gamma is identical for a call and a put at the same strike, and is always positive for long options.
Practical example (Nifty)
Illustrative — Nifty spot 24500, lot size 75
Nifty at 24,500, two days to weekly expiry. Your 24,500 CE has Delta 0.50 and Gamma 0.006. Nifty jumps 50 points to 24,550. New Delta ≈ 0.50 + (0.006 × 50) = 0.80. The option now moves at ₹0.80 per point instead of ₹0.50 — your exposure grew 60% from a single move. For a seller of that call, the loss is accelerating: what started as a ₹0.50/point liability is now ₹0.80/point and climbing.
Practical trading impact
Long Gamma (buying options) rewards big, fast moves and forgives being early; short Gamma (selling) punishes trends and rewards calm.
Gamma risk peaks on expiry day — size positions smaller and adjust sooner when short ATM options into expiry.
Gamma and Theta are inseparable: you cannot be long Gamma without paying Theta, or collect Theta without being short Gamma.
Use Gamma to anticipate how much re-hedging a Delta-neutral book will need — high Gamma means frequent adjustments.
Common mistakes
Selling naked ATM weekly options for the 'easy' Theta and ignoring the Gamma that turns a small move into a large, accelerating loss.
Underestimating how fast Delta shifts near expiry, then getting run over on a 'small' 40-point Nifty move.
Holding long options for Gamma but never actually scalping the movement, so Theta quietly eats the position.
Assuming a Delta-neutral position stays neutral — high Gamma means it un-hedges itself with every move.
Professional usage
Professional premium sellers respect Gamma above almost everything: they avoid or heavily reduce short ATM exposure in the final 1–2 days, keep positions small enough to survive a Gamma-driven gap, and adjust the tested side early rather than hoping. Long-Gamma traders, by contrast, deliberately buy Gamma before expected volatility (results, RBI policy, Budget) and scalp the underlying against it.
Key takeaway
Gamma is the acceleration of your directional exposure. It makes long options forgiving and short options dangerous — especially at-the-money and especially near expiry. Every Theta you collect is Gamma risk you have taken on.
Frequently asked questions
What is Gamma in options?
Gamma measures how fast Delta changes when the underlying moves ₹1. It is the acceleration of an option's directional exposure and is highest for at-the-money options near expiry.
Why is Gamma highest at-the-money?
Because a small move around the strike causes the biggest change in the probability of finishing ITM, so Delta shifts fastest there. Deep ITM/OTM options have Delta near 1 or 0, which barely changes.
What does long Gamma vs short Gamma mean?
Long Gamma (option buyers) gain favourable curvature — exposure grows in your favour on moves. Short Gamma (option sellers) face accelerating losses when the market trends against them.
Why is Gamma dangerous on expiry day?
Gamma spikes as time to expiry approaches zero. A small Nifty move can swing an ATM option's Delta dramatically, causing outsized, fast losses for sellers.
What is Gamma scalping?
Holding long options and trading the underlying against the Delta changes Gamma creates — effectively buying low and selling high as the position re-hedges, to harvest movement while paying Theta.
Is Gamma the same for calls and puts?
Yes. At the same strike and expiry, a call and a put have identical Gamma.
How does Gamma relate to Theta?
They are opposites in the trade-off: long Gamma positions pay Theta; short Gamma positions collect Theta. You cannot have positive Gamma and positive Theta at once.
Does Gamma change with volatility?
Yes. Lower implied volatility concentrates Gamma sharply at the ATM strike; higher volatility spreads it out across strikes and lowers the peak.
Which strategies are short Gamma?
Iron Condors, short straddles, short strangles, covered calls and cash-secured puts are all short Gamma — they earn Theta but suffer on large moves.
Should beginners worry about Gamma?
Yes, especially before selling options into expiry. Beginners who understand Gamma avoid the classic trap of collecting small Theta while carrying huge, accelerating tail risk.
How do I read and use Gamma from a broker option chain?
Gamma is shown per share alongside the other Greeks; multiply it by the expected point move to estimate how much your Delta will change. If a Nifty option shows Gamma 0.004 and you expect a 50-point move, Delta will shift by about 0.004 × 50 = 0.20. Traders use this to anticipate how quickly a hedge will drift.
How does Gamma influence my position sizing as a seller?
Because short-Gamma losses accelerate, size by the worst-case move, not the average day. A practical rule for expiry-day ATM selling is to cut lots sharply — often to a quarter or less of your normal size — since a 40–50 point Nifty move can produce a loss several times the premium collected. Size so a Gamma-driven gap does not breach your risk limit.
Is Gamma larger on Bank Nifty or Nifty options?
Per-share Gamma is higher when the underlying price is lower and volatility is lower, so at equal moneyness the raw Gamma numbers differ, but the practical point is that Bank Nifty's bigger point swings make its Gamma bite harder in rupees. A Bank Nifty ATM seller near expiry faces faster Delta changes in rupee terms because the index itself moves more.
Why does Gamma explode on weekly expiry but stay tame on monthly options?
Gamma is inversely related to the square root of time to expiry, so as time shrinks toward zero it spikes for ATM strikes. A weekly option in its final day has enormous ATM Gamma, while a monthly with three weeks left has a broad, gentle Gamma curve. This is why weekly ATM sellers face far more re-hedging and tail risk.
How does India VIX affect Gamma?
Lower India VIX (low IV) concentrates Gamma into a tall, narrow peak right at the ATM strike, making ATM options extremely twitchy. Higher VIX spreads Gamma across a wider band of strikes and lowers the peak, so exposure is less concentrated but affects more strikes. Calm markets paradoxically make ATM Gamma risk sharper.
What is peak Gamma and where does it sit?
Peak Gamma is the strike with the highest Gamma, which is the at-the-money strike, and its height grows as expiry nears. On expiry day the ATM strike has near-vertical Gamma, so the option's Delta can flip from 0.3 to 0.7 on a small move. Knowing where peak Gamma sits tells you which strike is most dangerous to be short.
How is Gamma risk different for buyers versus sellers in rupee terms?
For a buyer, long Gamma is a free upgrade — a favourable move makes gains accelerate and an adverse move makes losses decelerate, the cost being Theta paid daily. For a seller, short Gamma means the opposite: losing moves accelerate and winning moves fade, so a ₹0.50/point liability can become ₹0.90/point after one push. Buyers pay for curvature; sellers get paid to carry its danger.
What is the relationship between Gamma and Vega?
Both peak for ATM options, but they measure different things: Gamma is sensitivity of Delta to the underlying's price, Vega is sensitivity of price to implied volatility. Long options are long both. A key difference is that Gamma concentrates near expiry while Vega shrinks near expiry, so weeklies are high-Gamma but low-Vega and monthlies are the reverse.
Does Gamma scalping actually make money for retail traders in India?
It can, but only if realised volatility exceeds the implied volatility you paid, and if brokerage plus STT and slippage on frequent futures adjustments do not eat the gains. In practice, the transaction costs of re-hedging Nifty or Bank Nifty futures many times a day make retail Gamma scalping hard; it favours a big, fast realised move over a choppy grind.
Why can a short straddle lose money even if it stays roughly Delta-neutral?
Because Gamma re-creates directional exposure with every move. As the index moves toward one leg, that leg's Delta grows faster than the other leg's shrinks, so the position becomes net directional against you and losses accelerate. Delta-neutral at one instant does not mean neutral after the market moves.
How much re-hedging does high Gamma force on a Delta-neutral book?
High Gamma means Delta drifts quickly, so a neutral book un-hedges itself with every move and needs frequent adjustment. Near expiry the required re-hedging can be almost continuous, which is why professionals reduce ATM exposure into the final sessions rather than fight constant Delta drift and its transaction costs.
Is high Gamma always a good thing for an option buyer?
Not necessarily — high Gamma comes with high Theta. A weekly ATM long has strong Gamma but bleeds heavily each day, so if the big move does not arrive quickly, time decay overwhelms the favourable curvature. Long Gamma only pays off if the underlying actually moves enough to justify the Theta you are paying.
What is the difference between Gamma and Charm?
Both change your Delta, but for different reasons: Gamma changes Delta when the underlying moves, while Charm changes Delta as time passes. Near expiry both are large — Gamma makes Delta lurch on price moves and Charm drags it toward 0 or 1 overnight — which is why expiry-week hedges need constant attention.
Voice search & related questions
Natural-language questions people ask about Gamma.
What is Gamma risk in simple words?
It is the risk that your Delta changes fast when the market moves. For option sellers it means losses can accelerate quickly, especially near expiry.
Why is selling options on expiry day so risky?
Because Gamma is highest then, so a small Nifty move can swing your Delta and turn a tiny loss into a big, fast one.
How do I reduce Gamma risk when I sell options?
Sell further out-of-the-money, avoid the last day or two of expiry, and size small. Lower Gamma strikes change their Delta more slowly.
When is Gamma at its highest?
For at-the-money options in the final sessions before expiry. That is when Delta reacts most sharply to a move.
Should I buy weekly options just for the high Gamma?
Only if you expect a quick, sizable move. High Gamma comes with heavy daily Theta, so a flat market will bleed your premium away.
Can I profit from Gamma without predicting direction?
Yes, through Gamma scalping — hold long options and trade the underlying against the Delta changes. But costs and Theta make it hard for retail traders.
Does Gamma affect calls and puts the same way?
Yes. At the same strike and expiry, a call and a put have identical Gamma.
Why did my Delta-neutral trade suddenly become directional?
Because of Gamma. When the index moved, one leg's Delta grew faster than the other's, so your position stopped being neutral.
Educational content only — not investment advice. Greek values are illustrative and computed from a Black-Scholes model. Options trading involves substantial risk. See our Risk Disclosure and SEBI Disclaimer.