Gamma Γ
Rate of change of Delta for a ₹1 move in the underlying.
What is Gamma? 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.
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.
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.
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, lot size 75
Nifty at 20,000, two days to weekly expiry. Your 20,000 CE has Delta 0.50 and Gamma 0.006. Nifty jumps 50 points to 20,050. 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.
Mistakes traders make
- 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.
What professionals do
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?
Why is Gamma highest at-the-money?
What does long Gamma vs short Gamma mean?
Why is Gamma dangerous on expiry day?
What is Gamma scalping?
Is Gamma the same for calls and puts?
How does Gamma relate to Theta?
Does Gamma change with volatility?
Which strategies are short Gamma?
Should beginners worry about Gamma?
Sources & references
Educational content only — not investment advice.