Koilwar is a Sub-District (Tehsil/Block/Mandal) in the Bhojpur District of Bihar. As par Census 2011 information the sub-district code of Koilwar is 01424. There are about 14 sub-districts in Bhojpur and Koilwar is one of them. Agiaon, Arrah, Barhara, Behea, Charpokhari, Garhani, Jagdishpur, Piro, Sahar, Sandesh, Shahpur, Tarari, Udwant Nagar etc. are other sub-districts in Bhojpur.There are about 69 villages in Koilwar sub-district, which you can browse from villages list.