Why Is the Delta of an ATM Option Approximately 0.5 (Or -0.5)?

The Delta of an At-the-Money (ATM) option is close to 0.5 because it reflects a roughly 50% chance that the option will expire In-the-Money (ITM). If the underlying price moves up by $1, there is a high probability the call option will gain value, and a Delta of 0.5 suggests the option price will capture half of that $1 move.

This represents the point of maximum uncertainty regarding the option's final intrinsic value.