At the Money
An option is 'at the money' (ATM) when the strike price is equal to or very close to the current market price of the underlying stock, resulting in minimal or zero intrinsic value.
At-the-money options occupy the midpoint of the moneyness spectrum. The strike price and the current stock price are essentially identical, which means the option has little to no intrinsic value but often commands the highest amount of time value. This makes ATM options particularly sensitive to implied volatility changes and time decay — the two forces that most influence extrinsic value.
ATM options carry a delta of approximately 0.50 for calls and -0.50 for puts, reflecting roughly a 50-50 chance of expiring in the money. This makes them the most balanced directional bet: a $1 increase in the stock will add roughly $0.50 to an ATM call's value. For traders who want a moderate exposure to price movement without paying the full intrinsic value cost of an ITM option, ATM options are often the preferred starting point.
Because time value is maximized at the money, ATM options are the most sensitive to theta (time decay). An ATM option loses its time value the fastest in absolute dollar terms as expiration approaches, even though ITM options may lose more in relative intrinsic value during a large adverse move. Options sellers who write ATM straddles or short-term ATM covered calls are explicitly targeting this elevated time-value erosion as a source of income.
ATM options also have the highest vega of any strike, meaning their premium changes the most (in dollar terms) for a given change in implied volatility. A volatility spike benefits ATM option buyers and hurts ATM option sellers most dramatically. This is why traders who anticipate a volatility expansion event — such as an earnings announcement or a major economic report — often buy ATM straddles to profit regardless of price direction.
In practice, it is rare for the stock price to sit exactly at a listed strike. Traders often refer to the nearest available strike as 'at the money.' The CBOE calculates the at-the-money strike for index products like the VIX using a weighted average of nearby option premiums, adding nuance to the concept for index traders.