Koilwar is Taluka (Tehsil) in Bhojpur district of Bihar state. Koilwar has 12 areas (postal offices).
| Pin code | Area | District | Taluka | Postal Status |
|---|---|---|---|---|
| 802163 | Babhangawan PIN Code | Bhojpur | Koilwar | Branch Office |
| 802163 | Babura PIN Code | Bhojpur | Koilwar | Branch Office |
| 802163 | Bagmajhauan PIN Code | Bhojpur | Koilwar | Branch Office |
| 802163 | Bandhu Chhapra PIN Code | Bhojpur | Koilwar | Branch Office |
| 802161 | Jamira PIN Code | Bhojpur | Koilwar | Branch Office |
| 802160 | Katkaira PIN Code | Bhojpur | Koilwar | Branch Office |
| 802352 | Nasaratpur PIN Code | Bhojpur | Koilwar | Branch Office |
| 802163 | Naya Mohamad Pur PIN Code | Bhojpur | Koilwar | Sub Office |
| 802160 | Pareo PIN Code | Bhojpur | Koilwar | Branch Office |
| 802163 | Phuhan PIN Code | Bhojpur | Koilwar | Branch Office |
| 802352 | Pratappur PIN Code | Bhojpur | Koilwar | Branch Office |
| 802163 | Purana Haripur PIN Code | Bhojpur | Koilwar | Branch Office |