It is a surface area of 104 square kilometres (40 sq mi), circumference of 63 kilometres (39 mi), depth of 94 metres (308 ft) and is located at an altitude of 514 metres (1,686 ft).

Lake Inawashiro was formed some 30–40,000 years ago when a tectonic depression was dammed by a major eruption and pyroclastic flow from Mount Bandai.

The water level was considerably less during the Jōmon period as numerous artifacts and ceramic fragments have been found offshore.

The lake water is an important source for irrigation in the Aizu region of western Fukushima Prefecture.

A third canal completed in 1915 supplies the city of Kōriyama with drinking and industrial water.