The 27.6-square-kilometre (10.7 sq mi) lake is located on the border of Øvre Eiker Municipality in Buskerud county and Holmestrand Municipality in Vestfold county (the majority of the lake is in Buskerud).

Eikeren lake also receives water flowing into it from the rivers Hakavikelva and Steinbruelva.

Through this strait, water flows at an average rate of 7 cubic metres per second (250 cu ft/s).

[4][5] During the summer season, Eikeren is served by tourist boat M/S Eikern which runs between the villages of Eidsfoss and Vestfossen.

In 1903, the steamship Stadshauptmand Schwartz carried regular traffic and provided a link between the Kongsberg Railway (Kongsbergbanen) and the Tønsberg–Eidsfoss Line.