Gamma is the Greek that turns small underlying moves into big P&L swings. Why it peaks on expiry day, and why selling naked options near expiry can ruin accounts.
Gamma measures how much Delta itself changes for every ₹1 move in the underlying. If a call has Delta 0.40 and Gamma 0.05, then a ₹1 rise in the underlying makes Delta become 0.45.
Gamma is the second-derivative Greek — it tells you how your directional exposure shifts as the market moves. Most retail traders ignore it. They learn about it the hard way when they sell options into expiry and a small move turns into a big loss.
Gamma is highest where Delta changes fastest — at the at-the-money strike, where a small move flips the option from OTM-ish to ITM-ish.
Gamma also peaks as expiry approaches. With 30 days left, an ATM option's Delta might shift from 0.50 to 0.55 on a small move. With 1 day left, the same move can shift Delta from 0.50 to 0.80 — the option is suddenly almost-in-the-money with much less time for things to change.
Practical implication: an ATM option held into the last day of expiry has 5-10x more Gamma than the same option had a week earlier. Position risk grows even though the absolute price might be smaller.
When you sell an option, you collect Theta daily — that's the income. But you're short Gamma — meaning if the underlying moves toward your strike, your Delta swings against you fast.
Worked example: you sell a NIFTY 22,000 call for ₹40 with NIFTY at 21,950. Your Delta is +0.40 (short call = negative Delta from the call, but you're benefiting from time decay). NIFTY rallies to 22,050 — your short call is now ATM. Delta has flipped from +0.40 to -0.50. Your position is now hurting you on every further point up, AND the move past your strike just cost you ₹50 × 25 = ₹1,250 per lot beyond what Theta is paying back.
This is why expiry-day option selling is so dangerous despite the high Theta. Gamma risk peaks at the same moment Theta peaks.
Some traders intentionally take LONG Gamma positions (long straddles) and trade the underlying around them. Each time the underlying moves, the long straddle's Delta swings; the trader can hedge by trading the underlying back to flat Delta — harvesting the price change as profit.
This is called gamma scalping. It works when realized volatility (actual movement) exceeds implied volatility (priced-in expectation). When IV is cheap relative to realised, long Gamma + Delta hedging produces a positive expected return.
Retail traders don't typically gamma scalp at scale (transaction costs eat the edge for small positions) but understanding the mechanism explains why institutional desks pay up for ATM straddles when IV is low.
Mathematically, Gamma is the second derivative of option price with respect to underlying. It's a convex function for both calls and puts, so the second derivative is always positive. For option buyers this is good (long Gamma); for sellers it means risk increases on adverse moves.
Because Theta is also peaking. The bet is that the market stays close to current spot for the few hours remaining, and the Theta collected exceeds the Gamma losses if the market moves. It's a high-Sharpe but fat-tailed strategy — small wins most days, occasional ruinous losses.
Yes — same mechanics. But individual stock options have lower IV than indices for most names, so Gamma is lower in absolute terms. The biggest Gamma risks in Indian markets remain index options near expiry.
Strota's strategy builder shows net Gamma for any multi-leg position alongside Delta, Theta, and Vega. Broker terminals typically also display option Greeks per position in the F&O tab.
Yes — it's just a hedging strategy combining long options and underlying trades. There's no special regulatory treatment. The practical barrier for retail is transaction costs: small positions don't generate enough scalp revenue to overcome STT and brokerage.