By 2051, Bihar's maximum population will be 20 crore and minimum 16 crore, said the study by the Patna-based AN Sinha Institute of Social Studies.
In special issue of the institute's journal, director Deewakar said the rising population will pose a big challenge to the state.
"The decision makers will have to provide food, qualitative education, health, employment and other facilities for ... all," he said.
According to the study, Bihar's population can be stabilized by increasing awareness and spreading literacy.
Last year, the Bihar government launched a major initiative to stabilise population and train adolescents on reproductive health and family planning.
Bihar is one of the most densely populated states in India.
In 2001, with an average density of 1,102, Bihar was ahead of West Bengal with 1,029 and Kerala, which is at third place with 859.
In 2011, 211 more people inhabited every sq km of Bihar compared to 2001.
Patna: Bihar's population will be 20 crore by the middle of this century, according to a study.
First Published: Thursday, January 17, 2013, 18:30