A method for calculating a distance to empty (DTE) when setting a path of navigation is provided. The method includes receiving path search cases from a navigation and determining whether the transmitted path search case is a path cancellation, a vehicle arriving at a destination, or the navigation searching for the path. The method determines whether the transmitted path search case is an initially set path or a reset path. When the transmitted path search case is none of the above the method determines whether there is a currently guided. When the path is initially set, the path is reset after, or the path is currently being guided, among the path search cases, a path reflected DTE is displayed through the navigation; and the path reflected DTE is calculated in real time and path reflected prediction fuel efficiency is calculated, after displaying the path reflected DTE.