GEX = Γ × OI (contracts) × lot × S² × 0.01

₹ change in delta-notional for a 1% NIFTY move. Lot — (—); provider OI is in units and is divided by lot to get contracts.

Call and Put GEX are unsigned. Net GEX applies positioning signs: calls —1, puts —1 (fixed convention).

Gamma: provider value when supplied, else Black-Scholes from the provider IV (r = 6.5%). Contracts with neither are excluded.

Gamma Flip: Black-Scholes gamma is recomputed from each contract's IV at every hypothetical spot (±—%, step —); the flip is the interpolated sign change of aggregate signed GEX.

Option-chain OI does not reveal whether dealers are long or short. This is an assumption-based estimate, not dealer inventory or hedging flow.