Bihar is located in the eastern part of the country. Bihar lies mid-way between the humid West Bengal in the east and the sub humid Uttar Pradesh in the west. It is bounded by Nepal in the north and by Jharkhand in the south. The Bihar plain is divided into two unequal halves by the river Ganga which flows through the middle from west to east.

The total area covered by the state of Bihar is 94,163 sq. km. the state is located between 21°-58'-10" N ~ 27°-31'-15" N latitude and between 82°-19'-50" E ~ 88°-17'-40" E longitude. Its average elevation above sea level is 173 Feet.

Bihar is mainly a vast stretch of very fertile flat land. It has several rivers namely Ganga, Son, Bagmati, Kosi, Budhi Gandak, and Falgu. Central parts of Bihar have some small hills, for example the Rajgir hills.

The Himalayan Mountains are to the north of Bihar, in Nepal. To the south is the Chota Nagpur plateau, which was part of Bihar until 2000 but now is part of a separate state called Jharkhand.