Harpurnag is a village in Mehsi tehsil in district of Purba Champaran, Bihar, India. As per the data provided by Census of India in 2011, total population of Harpurnag was 3,550 which includes 1,832 males and 1,718 females. Harpurnag covers 185 ha area. Pincode of Harpurnag is 845426.