ATM IV
The implied volatility of the at-the-money strike — the market's purest single-number read on expected price swings.
Definition
ATM IV (At-the-Money Implied Volatility) is the implied volatility read from the option whose strike is closest to the current spot price of the underlying. On NSE, where Nifty 50 strikes are spaced 50 points apart, the ATM strike is the one immediately at or just below spot. Because the ATM option has no intrinsic value — it is entirely time value — its premium is a direct and clean reflection of how much movement the market expects before expiry. ATM IV is also the starting point of the volatility smile: wings (far OTM strikes) typically carry higher IV due to skew, while ATM represents the base level of expected volatility.
Why it matters
ATM IV is the reference traders reach for first because it has the highest vega of any strike and the deepest liquidity — bid-ask spreads are tightest here, so the price signal is most reliable. When ATM IV is elevated relative to its recent history, option premiums are expensive and strategies that sell options (short straddles, iron condors) are more attractively priced. When ATM IV is low, premium income is thin and buying protection for a directional bet or portfolio hedge is cheap. On weekly NSE expiries — Nifty expires every Thursday, Bank Nifty every Wednesday — ATM IV can collapse dramatically in the final session as theta accelerates, a dynamic every expiry-day trader must understand. Comparing ATM IV between near and far expiries also reveals the term structure: whether the market is pricing in a near-term event risk or treats volatility as flat across time.
Formula
ATM IV is not calculated directly — it is solved iteratively. Given the ATM option's market price P, the Black-Scholes formula is inverted to find the single σ (sigma) that satisfies: P = BS(S, K, T, r, σ), where S is spot, K is the ATM strike, T is time to expiry in years, and r is the risk-free rate. Newton-Raphson or bisection methods converge quickly because the ATM vega (d(BS)/dσ) is at its maximum, making the inversion numerically stable. The result is expressed as an annualised percentage.
Example
Suppose Nifty spot is at 24,350 and the nearest ATM strike is 24,350. The weekly call expiring in 5 days is quoted at ₹105 and the corresponding put at ₹98. Solving Black-Scholes for both gives an IV of roughly 14 percent annualised (illustrative). A trader observing that the same ATM strike carried 22 percent IV last month can conclude that options are currently cheap relative to that recent period — potentially favouring long-vega positions such as a straddle. All figures are hypothetical.
See ATM IV live on TradePulse
TradePulse highlights the ATM row on every option chain so you can read the IV benchmark at a glance.