Dharnai is a village in Sonbhadra Banshi Suryapur tehsil in district of Arwal, Bihar, India. As per the data provided by Census of India in 2011, total population of Dharnai was 2,473 which includes 1,240 males and 1,233 females. Dharnai covers 208 ha area. Pincode of Dharnai is 804421.