Introductory Context
"Gamma peaks at the ATM strike and decreases toward both deep ITM and deep OTM strikes. The gamma distribution forms a bell curve centred at ATM. Near expiry, this bell curve becomes extremely tall and narrow, creating the explosive ATM gamma of expiry Thursday. Higher IV flattens and widens the distribution, spreading gamma across more strikes."
The Gamma Distribution Across Strikes
With Nifty at 24,000, approximate gamma values for a weekly option (7 days, normal VIX):
• 22,000 CE (deep ITM): gamma ≈ 0.0003 — very low
• 23,000 CE (ITM): gamma ≈ 0.0010 — moderate
• 23,500 CE (slightly ITM): gamma ≈ 0.0015
• 24,000 CE (ATM): gamma ≈ 0.0025 — maximum
• 24,500 CE (slightly OTM): gamma ≈ 0.0015 — symmetric with slightly ITM
• 25,000 CE (OTM): gamma ≈ 0.0008 — declining
• 26,000 CE (deep OTM): gamma ≈ 0.0001 — minimal
The pattern: gamma peaks at ATM and falls approximately symmetrically on both sides. ATM options are the most dynamically sensitive. Deep ITM behave like futures with stable delta. Deep OTM are insensitive — small underlying moves create almost no delta change.
How Time Affects the Gamma Distribution
Near Expiry — Tall and Narrow Bell Curve
As expiry approaches, ATM gamma increases dramatically and the range of strikes with significant gamma shrinks. With 1 day remaining: ATM gamma ≈ 0.008 (3× the 7-day level), but gamma at ±100 points away ≈ 0.001. Gamma is concentrated almost entirely at the ATM strike. Near expiry, only ATM options have significant gamma — OTM options are effectively inert unless a very large move occurs.
Far From Expiry — Shorter and Wider Bell Curve
With 30+ days remaining: ATM gamma is lower (≈0.0008) but distributed more evenly across a wider range of strikes. OTM strikes 300 points away still have meaningful gamma — they can experience meaningful delta changes on large moves.
How IV Affects the Gamma Distribution
Higher IV flattens and widens the gamma distribution — OTM strike gamma is higher, ATM gamma is slightly lower. Lower IV concentrates gamma at ATM and reduces it at OTM strikes. Practical implication: in high-VIX environments, OTM options have higher gamma than usual, giving buyers more dynamic sensitivity per position than at the same strike distance in low-VIX conditions.
Gamma Expiry Week Evolution — Monday to Thursday
Monday (5 days): moderate ATM gamma, meaningful gamma across ±200 points. Moderate sensitivity.
Tuesday-Wednesday: ATM gamma rising, gamma at ±100 points still meaningful.
Wednesday afternoon (2 days): ATM gamma significantly elevated. OTM gamma collapsing. Chain becoming bi-modal.
Thursday (final session): ATM gamma at maximum. OTM gamma near zero. ATM options explosive — 50-point moves create 20–40% premium changes. OTM options static.
Tuesday OTM Gamma Collapse
By Thuesday of expiry week, OTM options have near-zero gamma. The position is essentially binary: either Nifty makes a large sudden move and the option expires ITM, or it expires worthless. There is no intermediate positive outcome from theta or gamma. Holding OTM options into Tuesday without a clear large-move catalyst means exit is almost always the correct decision.