Donji Popovac is located in the City of Slunj, in Karlovac County at an elevation of 360 meters above sea level and it covers the area of 0.73 km² (0.28 sq. miles). According to the 2011 census report, there were 17 inhabitants. It is entirely populated by Croats. Nearby places: Lumbardenik, Gornji Popovac, Novo Selo, Jame, Slunj, Podmelnica, Donji Lađevac, Rastoke, Gornji Kremen and Mali Vuković.