The population of Bihiya sub-district in 2001 was 139,374; this increased to 151,722 by 2011. Likewise, the population of the town of Bihiya itself increased by 28.8%, from 20,741 in 2001 to 26,707 in 2011. The district overall had a sex ratio of 918 in 2011 (917 in rural areas, and 920 in the town of Bihiya itself). In the 0-6 age group, the ratio was higher: 923 in rural areas, 964 in the town of Bihiya, and 928 overall. Members of scheduled castes formed 16.65% of the sub-district's total population, and 9.09% of the population of the town of Bihiya. Likewise, members of scheduled tribes constituted 1.39% of the total population of the sub-district, and 3.21% of the population of the town of Bihiya. The 3.21% of scheduled tribe members in the town of Bihiya was the highest percentage of towns in Bhojpur district in 2011. The literacy rate of the sub-district as a whole was 67.8% in 2011 (69.4% in rural areas, and 78.2% in the town of Bihiya itself).