Gamma Γ
Rate of change of Delta for a ₹1 move in the underlying.
Quick Answer
Gamma measures how fast Delta changes as the underlying moves ₹1. If a Nifty at-the-money option has a Gamma of 0.006, a 50-point rally lifts its Delta from 0.50 to about 0.80. Gamma is highest for at-the-money options and rises sharply into expiry, which is what makes short at-the-money positions dangerous.
Gamma — definition
Gamma is the second-order option Greek measuring the rate of change of Delta for a one-rupee move in the underlying, quoted per ₹1 of spot movement.
Gamma — key takeaways
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.
Gamma at a glance
| 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 |
Gamma in simple words
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.
How Gamma behaves — visual
Gamma — 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 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.
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.
Gamma — practical example (Nifty)
Illustrative — Nifty spot 24500, lot size 65
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.
Why Gamma matters in practice
- 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 misconceptions about Gamma
- Misconception: High Gamma is always a good thing for an option buyer.
Reality: High Gamma comes bundled 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 curvature you paid for. - Misconception: Gamma scalping is reliable easy money for retail traders.
Reality: Gamma scalping pays only when realised volatility exceeds the implied volatility you paid — and after brokerage, STT and slippage on the frequent futures adjustments. In practice those frictions eat most of the edge for small Indian retail accounts. - Misconception: A short straddle that stays roughly Delta-neutral cannot lose much.
Reality: Gamma re-creates directional exposure with every move: as the index moves toward one leg, that leg's Delta grows faster than the other shrinks, so the position becomes directional exactly when the move is against you.
Common mistakes with Gamma
- 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.
How professionals use Gamma
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.
Gamma — 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.
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.
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.
Voice search: Gamma 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.
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.
People also ask about Gamma
These questions are answered in detail on their own pages:
Sources & references
- Black, F. & Scholes, M. (1973). “The Pricing of Options and Corporate Liabilities.” Journal of Political Economy, 81(3), 637–654.
- Hull, J. C. Options, Futures, and Other Derivatives (10th ed.). Pearson, 2017.
- Natenberg, S. Option Volatility and Pricing (2nd ed.). McGraw-Hill, 2015.
- NSE India — Equity derivatives (futures & options) product specifications.
Published 22 April 2026. Educational content only — not investment advice.