The Bos originates at the Zallenberg at an elevation of 490 metres (1,610 ft) above sea level.

It passes the village of Bosen, part of Nohfelden, on the north and then, after about 3.4 kilometres (2.1 mi), it reaches the Bostalsee.

Its mouth is located about 300 metres (980 ft) south of the village of Eckelhausen, also part of Nohfelden.

On its 5.8-kilometre-long (3.6 mi) course, the Bos drops 111 metres (364 ft), which corresponds to a mean bottom slope of 1.91%.

It drains a 12,634 square kilometres (4,878 sq mi) drainage basin.