Lake Hrutsvatn has an area of 2,2 km². Its greatest depth is 1,5 m and it is situated 3,5 m above sea level. Its discharge is a ditch, which was dug in 1910 and tributes to the rivers Thverlaekur and Andalaekur on their way to lake Frakkavatn.
Road no. 275 passes near the lake and bogs surround it from three sides. The catch consists of small lake char and brown trout. The lake has been netted quite frequently. According to the legend the lake is occupied by a brown ram, which is seen only on autumn nights, before the weather changes for the worse.
The distance from the capital is about 85 km and 30 km from Selfoss.