Sperillen is located in Ådal in Ringerike municipality in the county of Buskerud. The lake has an area of 37 km², has a volume of 13 km³ [], is 123 meters deep at its deepest, and lies 150 meters above sea level
The rivers Begna from the valley of Begnadalen and Urula from the valley of Hedalen flow into the lake from the north. At south, a hydro-electric power station is located at Ringmoen. The lake is well known for its fisheries, and the lake is one of the few with a commercial fishery. Common species are whitefish, char, European perch and trout.